Merge tag 'hyperv-next-signed' of git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux

Pull hyper-v updates from Wei Liu:

- a series from Andrea to support channel reassignment

- a series from Vitaly to clean up Vmbus message handling

- a series from Michael to clean up and augment hyperv-tlfs.h

- patches from Andy to clean up GUID usage in Hyper-V code

- a few other misc patches

* tag 'hyperv-next-signed' of git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux: (29 commits)
Drivers: hv: vmbus: Resolve more races involving init_vp_index()
Drivers: hv: vmbus: Resolve race between init_vp_index() and CPU hotplug
vmbus: Replace zero-length array with flexible-array
Driver: hv: vmbus: drop a no long applicable comment
hyper-v: Switch to use UUID types directly
hyper-v: Replace open-coded variant of %*phN specifier
hyper-v: Supply GUID pointer to printf() like functions
hyper-v: Use UUID API for exporting the GUID (part 2)
asm-generic/hyperv: Add definitions for Get/SetVpRegister hypercalls
x86/hyperv: Split hyperv-tlfs.h into arch dependent and independent files
x86/hyperv: Remove HV_PROCESSOR_POWER_STATE #defines
KVM: x86: hyperv: Remove duplicate definitions of Reference TSC Page
drivers: hv: remove redundant assignment to pointer primary_channel
scsi: storvsc: Re-init stor_chns when a channel interrupt is re-assigned
Drivers: hv: vmbus: Introduce the CHANNELMSG_MODIFYCHANNEL message type
Drivers: hv: vmbus: Synchronize init_vp_index() vs. CPU hotplug
Drivers: hv: vmbus: Remove the unused HV_LOCALIZED channel affinity logic
PCI: hv: Prepare hv_compose_msi_msg() for the VMBus-channel-interrupt-to-vCPU reassignment functionality
Drivers: hv: vmbus: Use a spin lock for synchronizing channel scheduling vs. channel removal
hv_utils: Always execute the fcopy and vss callbacks in a tasklet
...

MAINTAINERS

···
 F:	drivers/scsi/storvsc_drv.c
 F:	drivers/uio/uio_hv_generic.c
 F:	drivers/video/fbdev/hyperv_fb.c
+F:	include/asm-generic/hyperv-tlfs.h
 F:	include/asm-generic/mshyperv.h
 F:	include/clocksource/hyperv_timer.h
 F:	include/linux/hyperv.h

arch/x86/include/asm/hyperv-tlfs.h

···
 
 #include <linux/types.h>
 #include <asm/page.h>
-
-/*
- * While not explicitly listed in the TLFS, Hyper-V always runs with a page size
- * of 4096. These definitions are used when communicating with Hyper-V using
- * guest physical pages and guest physical page addresses, since the guest page
- * size may not be 4096 on all architectures.
- */
-#define HV_HYP_PAGE_SHIFT      12
-#define HV_HYP_PAGE_SIZE       BIT(HV_HYP_PAGE_SHIFT)
-#define HV_HYP_PAGE_MASK       (~(HV_HYP_PAGE_SIZE - 1))
-
 /*
  * The below CPUID leaves are present if VersionAndFeatures.HypervisorPresent
  * is set by CPUID(HvCpuIdFunctionVersionAndFeatures).
···
 #define HYPERV_CPUID_MAX			0x4000ffff
 
 /*
- * Feature identification. EAX indicates which features are available
- * to the partition based upon the current partition privileges.
- * These are HYPERV_CPUID_FEATURES.EAX bits.
+ * Aliases for Group A features that have X64 in the name.
+ * On x86/x64 these are HYPERV_CPUID_FEATURES.EAX bits.
  */
 
-/* VP Runtime (HV_X64_MSR_VP_RUNTIME) available */
-#define HV_X64_MSR_VP_RUNTIME_AVAILABLE		BIT(0)
-/* Partition Reference Counter (HV_X64_MSR_TIME_REF_COUNT) available*/
-#define HV_MSR_TIME_REF_COUNT_AVAILABLE		BIT(1)
-/*
- * Basic SynIC MSRs (HV_X64_MSR_SCONTROL through HV_X64_MSR_EOM
- * and HV_X64_MSR_SINT0 through HV_X64_MSR_SINT15) available
- */
-#define HV_X64_MSR_SYNIC_AVAILABLE		BIT(2)
-/*
- * Synthetic Timer MSRs (HV_X64_MSR_STIMER0_CONFIG through
- * HV_X64_MSR_STIMER3_COUNT) available
- */
-#define HV_MSR_SYNTIMER_AVAILABLE		BIT(3)
-/*
- * APIC access MSRs (HV_X64_MSR_EOI, HV_X64_MSR_ICR and HV_X64_MSR_TPR)
- * are available
- */
-#define HV_X64_MSR_APIC_ACCESS_AVAILABLE	BIT(4)
-/* Hypercall MSRs (HV_X64_MSR_GUEST_OS_ID and HV_X64_MSR_HYPERCALL) available*/
-#define HV_X64_MSR_HYPERCALL_AVAILABLE		BIT(5)
-/* Access virtual processor index MSR (HV_X64_MSR_VP_INDEX) available*/
-#define HV_X64_MSR_VP_INDEX_AVAILABLE		BIT(6)
-/* Virtual system reset MSR (HV_X64_MSR_RESET) is available*/
-#define HV_X64_MSR_RESET_AVAILABLE		BIT(7)
-/*
- * Access statistics pages MSRs (HV_X64_MSR_STATS_PARTITION_RETAIL_PAGE,
- * HV_X64_MSR_STATS_PARTITION_INTERNAL_PAGE, HV_X64_MSR_STATS_VP_RETAIL_PAGE,
- * HV_X64_MSR_STATS_VP_INTERNAL_PAGE) available
- */
-#define HV_X64_MSR_STAT_PAGES_AVAILABLE		BIT(8)
-/* Partition reference TSC MSR is available */
-#define HV_MSR_REFERENCE_TSC_AVAILABLE		BIT(9)
-/* Partition Guest IDLE MSR is available */
-#define HV_X64_MSR_GUEST_IDLE_AVAILABLE		BIT(10)
-/*
- * There is a single feature flag that signifies if the partition has access
- * to MSRs with local APIC and TSC frequencies.
- */
-#define HV_X64_ACCESS_FREQUENCY_MSRS		BIT(11)
-/* AccessReenlightenmentControls privilege */
-#define HV_X64_ACCESS_REENLIGHTENMENT		BIT(13)
-/* AccessTscInvariantControls privilege */
-#define HV_X64_ACCESS_TSC_INVARIANT		BIT(15)
+#define HV_X64_MSR_VP_RUNTIME_AVAILABLE		\
+		HV_MSR_VP_RUNTIME_AVAILABLE
+#define HV_X64_MSR_SYNIC_AVAILABLE		\
+		HV_MSR_SYNIC_AVAILABLE
+#define HV_X64_MSR_APIC_ACCESS_AVAILABLE	\
+		HV_MSR_APIC_ACCESS_AVAILABLE
+#define HV_X64_MSR_HYPERCALL_AVAILABLE		\
+		HV_MSR_HYPERCALL_AVAILABLE
+#define HV_X64_MSR_VP_INDEX_AVAILABLE		\
+		HV_MSR_VP_INDEX_AVAILABLE
+#define HV_X64_MSR_RESET_AVAILABLE		\
+		HV_MSR_RESET_AVAILABLE
+#define HV_X64_MSR_GUEST_IDLE_AVAILABLE		\
+		HV_MSR_GUEST_IDLE_AVAILABLE
+#define HV_X64_ACCESS_FREQUENCY_MSRS		\
+		HV_ACCESS_FREQUENCY_MSRS
+#define HV_X64_ACCESS_REENLIGHTENMENT		\
+		HV_ACCESS_REENLIGHTENMENT
+#define HV_X64_ACCESS_TSC_INVARIANT		\
+		HV_ACCESS_TSC_INVARIANT
 
 /*
- * Feature identification: indicates which flags were specified at partition
- * creation. The format is the same as the partition creation flag structure
- * defined in section Partition Creation Flags.
- * These are HYPERV_CPUID_FEATURES.EBX bits.
+ * Aliases for Group B features that have X64 in the name.
+ * On x86/x64 these are HYPERV_CPUID_FEATURES.EBX bits.
  */
-#define HV_X64_CREATE_PARTITIONS		BIT(0)
-#define HV_X64_ACCESS_PARTITION_ID		BIT(1)
-#define HV_X64_ACCESS_MEMORY_POOL		BIT(2)
-#define HV_X64_ADJUST_MESSAGE_BUFFERS		BIT(3)
-#define HV_X64_POST_MESSAGES			BIT(4)
-#define HV_X64_SIGNAL_EVENTS			BIT(5)
-#define HV_X64_CREATE_PORT			BIT(6)
-#define HV_X64_CONNECT_PORT			BIT(7)
-#define HV_X64_ACCESS_STATS			BIT(8)
-#define HV_X64_DEBUGGING			BIT(11)
-#define HV_X64_CPU_POWER_MANAGEMENT		BIT(12)
+#define HV_X64_POST_MESSAGES		HV_POST_MESSAGES
+#define HV_X64_SIGNAL_EVENTS		HV_SIGNAL_EVENTS
 
 /*
- * Feature identification. EDX indicates which miscellaneous features
- * are available to the partition.
- * These are HYPERV_CPUID_FEATURES.EDX bits.
+ * Group D Features.  The bit assignments are custom to each architecture.
+ * On x86/x64 these are HYPERV_CPUID_FEATURES.EDX bits.
  */
 /* The MWAIT instruction is available (per section MONITOR / MWAIT) */
 #define HV_X64_MWAIT_AVAILABLE				BIT(0)
···
  * processor, except for virtual processors that are reported as sibling SMT
  * threads.
  */
-#define HV_X64_NO_NONARCH_CORESHARING                  BIT(18)
+#define HV_X64_NO_NONARCH_CORESHARING			BIT(18)
 
 /* Nested features. These are HYPERV_CPUID_NESTED_FEATURES.EAX bits. */
 #define HV_X64_NESTED_DIRECT_FLUSH			BIT(17)
···
 	} __packed;
 };
 
-/*
- * TSC page layout.
- */
-struct ms_hyperv_tsc_page {
-	volatile u32 tsc_sequence;
-	u32 reserved1;
-	volatile u64 tsc_scale;
-	volatile s64 tsc_offset;
-	u64 reserved2[509];
-}  __packed;
-
-/*
- * The guest OS needs to register the guest ID with the hypervisor.
- * The guest ID is a 64 bit entity and the structure of this ID is
- * specified in the Hyper-V specification:
- *
- * msdn.microsoft.com/en-us/library/windows/hardware/ff542653%28v=vs.85%29.aspx
- *
- * While the current guideline does not specify how Linux guest ID(s)
- * need to be generated, our plan is to publish the guidelines for
- * Linux and other guest operating systems that currently are hosted
- * on Hyper-V. The implementation here conforms to this yet
- * unpublished guidelines.
- *
- *
- * Bit(s)
- * 63 - Indicates if the OS is Open Source or not; 1 is Open Source
- * 62:56 - Os Type; Linux is 0x100
- * 55:48 - Distro specific identification
- * 47:16 - Linux kernel version number
- * 15:0  - Distro specific identification
- *
- *
- */
-
-#define HV_LINUX_VENDOR_ID              0x8100
-
 struct hv_reenlightenment_control {
 	__u64 vector:8;
 	__u64 reserved1:8;
···
 #define HV_X64_MSR_HYPERCALL_PAGE_ADDRESS_MASK	\
 		(~((1ull << HV_X64_MSR_HYPERCALL_PAGE_ADDRESS_SHIFT) - 1))
 
-/*
- * Crash notification (HV_X64_MSR_CRASH_CTL) flags.
- */
-#define HV_CRASH_CTL_CRASH_NOTIFY_MSG		BIT_ULL(62)
-#define HV_CRASH_CTL_CRASH_NOTIFY		BIT_ULL(63)
 #define HV_X64_MSR_CRASH_PARAMS		\
 		(1 + (HV_X64_MSR_CRASH_P4 - HV_X64_MSR_CRASH_P0))
 
 #define HV_IPI_LOW_VECTOR	0x10
 #define HV_IPI_HIGH_VECTOR	0xff
-
-/* Declare the various hypercall operations. */
-#define HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE	0x0002
-#define HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST	0x0003
-#define HVCALL_NOTIFY_LONG_SPIN_WAIT		0x0008
-#define HVCALL_SEND_IPI				0x000b
-#define HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE_EX  0x0013
-#define HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST_EX   0x0014
-#define HVCALL_SEND_IPI_EX			0x0015
-#define HVCALL_POST_MESSAGE			0x005c
-#define HVCALL_SIGNAL_EVENT			0x005d
-#define HVCALL_RETARGET_INTERRUPT		0x007e
-#define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_SPACE 0x00af
-#define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_LIST 0x00b0
 
 #define HV_X64_MSR_VP_ASSIST_PAGE_ENABLE	0x00000001
 #define HV_X64_MSR_VP_ASSIST_PAGE_ADDRESS_SHIFT	12
···
 #define HV_X64_MSR_TSC_REFERENCE_ENABLE		0x00000001
 #define HV_X64_MSR_TSC_REFERENCE_ADDRESS_SHIFT	12
 
-#define HV_PROCESSOR_POWER_STATE_C0		0
-#define HV_PROCESSOR_POWER_STATE_C1		1
-#define HV_PROCESSOR_POWER_STATE_C2		2
-#define HV_PROCESSOR_POWER_STATE_C3		3
-
-#define HV_FLUSH_ALL_PROCESSORS			BIT(0)
-#define HV_FLUSH_ALL_VIRTUAL_ADDRESS_SPACES	BIT(1)
-#define HV_FLUSH_NON_GLOBAL_MAPPINGS_ONLY	BIT(2)
-#define HV_FLUSH_USE_EXTENDED_RANGE_FORMAT	BIT(3)
-
-enum HV_GENERIC_SET_FORMAT {
-	HV_GENERIC_SET_SPARSE_4K,
-	HV_GENERIC_SET_ALL,
-};
-
-#define HV_PARTITION_ID_SELF                    ((u64)-1)
-
-#define HV_HYPERCALL_RESULT_MASK	GENMASK_ULL(15, 0)
-#define HV_HYPERCALL_FAST_BIT		BIT(16)
-#define HV_HYPERCALL_VARHEAD_OFFSET	17
-#define HV_HYPERCALL_REP_COMP_OFFSET	32
-#define HV_HYPERCALL_REP_COMP_MASK	GENMASK_ULL(43, 32)
-#define HV_HYPERCALL_REP_START_OFFSET	48
-#define HV_HYPERCALL_REP_START_MASK	GENMASK_ULL(59, 48)
-
-/* hypercall status code */
-#define HV_STATUS_SUCCESS			0
-#define HV_STATUS_INVALID_HYPERCALL_CODE	2
-#define HV_STATUS_INVALID_HYPERCALL_INPUT	3
-#define HV_STATUS_INVALID_ALIGNMENT		4
-#define HV_STATUS_INVALID_PARAMETER		5
-#define HV_STATUS_INSUFFICIENT_MEMORY		11
-#define HV_STATUS_INVALID_PORT_ID		17
-#define HV_STATUS_INVALID_CONNECTION_ID		18
-#define HV_STATUS_INSUFFICIENT_BUFFERS		19
-
-/*
- * The Hyper-V TimeRefCount register and the TSC
- * page provide a guest VM clock with 100ns tick rate
- */
-#define HV_CLOCK_HZ (NSEC_PER_SEC/100)
-
-typedef struct _HV_REFERENCE_TSC_PAGE {
-	__u32 tsc_sequence;
-	__u32 res1;
-	__u64 tsc_scale;
-	__s64 tsc_offset;
-}  __packed HV_REFERENCE_TSC_PAGE, *PHV_REFERENCE_TSC_PAGE;
-
-/* Define the number of synthetic interrupt sources. */
-#define HV_SYNIC_SINT_COUNT		(16)
-/* Define the expected SynIC version. */
-#define HV_SYNIC_VERSION_1		(0x1)
-/* Valid SynIC vectors are 16-255. */
-#define HV_SYNIC_FIRST_VALID_VECTOR	(16)
-
-#define HV_SYNIC_CONTROL_ENABLE		(1ULL << 0)
-#define HV_SYNIC_SIMP_ENABLE		(1ULL << 0)
-#define HV_SYNIC_SIEFP_ENABLE		(1ULL << 0)
-#define HV_SYNIC_SINT_MASKED		(1ULL << 16)
-#define HV_SYNIC_SINT_AUTO_EOI		(1ULL << 17)
-#define HV_SYNIC_SINT_VECTOR_MASK	(0xFF)
-
-#define HV_SYNIC_STIMER_COUNT		(4)
-
-/* Define synthetic interrupt controller message constants. */
-#define HV_MESSAGE_SIZE			(256)
-#define HV_MESSAGE_PAYLOAD_BYTE_COUNT	(240)
-#define HV_MESSAGE_PAYLOAD_QWORD_COUNT	(30)
 
 /* Define hypervisor message types. */
 enum hv_message_type {
···
 	HVMSG_GPA_INTERCEPT		= 0x80000001,
 
 	/* Timer notification messages. */
-	HVMSG_TIMER_EXPIRED			= 0x80000010,
+	HVMSG_TIMER_EXPIRED		= 0x80000010,
 
 	/* Error messages. */
 	HVMSG_INVALID_VP_REGISTER_VALUE	= 0x80000020,
 	HVMSG_UNRECOVERABLE_EXCEPTION	= 0x80000021,
-	HVMSG_UNSUPPORTED_FEATURE		= 0x80000022,
+	HVMSG_UNSUPPORTED_FEATURE	= 0x80000022,
 
 	/* Trace buffer complete messages. */
 	HVMSG_EVENTLOG_BUFFERCOMPLETE	= 0x80000040,
 
 	/* Platform-specific processor intercept messages. */
-	HVMSG_X64_IOPORT_INTERCEPT		= 0x80010000,
+	HVMSG_X64_IOPORT_INTERCEPT	= 0x80010000,
 	HVMSG_X64_MSR_INTERCEPT		= 0x80010001,
-	HVMSG_X64_CPUID_INTERCEPT		= 0x80010002,
+	HVMSG_X64_CPUID_INTERCEPT	= 0x80010002,
 	HVMSG_X64_EXCEPTION_INTERCEPT	= 0x80010003,
-	HVMSG_X64_APIC_EOI			= 0x80010004,
-	HVMSG_X64_LEGACY_FP_ERROR		= 0x80010005
+	HVMSG_X64_APIC_EOI		= 0x80010004,
+	HVMSG_X64_LEGACY_FP_ERROR	= 0x80010005
 };
-
-/* Define synthetic interrupt controller message flags. */
-union hv_message_flags {
-	__u8 asu8;
-	struct {
-		__u8 msg_pending:1;
-		__u8 reserved:7;
-	} __packed;
-};
-
-/* Define port identifier type. */
-union hv_port_id {
-	__u32 asu32;
-	struct {
-		__u32 id:24;
-		__u32 reserved:8;
-	} __packed u;
-};
-
-/* Define synthetic interrupt controller message header. */
-struct hv_message_header {
-	__u32 message_type;
-	__u8 payload_size;
-	union hv_message_flags message_flags;
-	__u8 reserved[2];
-	union {
-		__u64 sender;
-		union hv_port_id port;
-	};
-} __packed;
-
-/* Define synthetic interrupt controller message format. */
-struct hv_message {
-	struct hv_message_header header;
-	union {
-		__u64 payload[HV_MESSAGE_PAYLOAD_QWORD_COUNT];
-	} u;
-} __packed;
-
-/* Define the synthetic interrupt message page layout. */
-struct hv_message_page {
-	struct hv_message sint_message[HV_SYNIC_SINT_COUNT];
-} __packed;
-
-/* Define timer message payload structure. */
-struct hv_timer_message_payload {
-	__u32 timer_index;
-	__u32 reserved;
-	__u64 expiration_time;	/* When the timer expired */
-	__u64 delivery_time;	/* When the message was delivered */
-} __packed;
 
 struct hv_nested_enlightenments_control {
 	struct {
···
 
 #define HV_VMX_ENLIGHTENED_CLEAN_FIELD_ALL			0xFFFF
 
-/* Define synthetic interrupt controller flag constants. */
-#define HV_EVENT_FLAGS_COUNT		(256 * 8)
-#define HV_EVENT_FLAGS_LONG_COUNT	(256 / sizeof(unsigned long))
-
-/*
- * Synthetic timer configuration.
- */
-union hv_stimer_config {
-	u64 as_uint64;
-	struct {
-		u64 enable:1;
-		u64 periodic:1;
-		u64 lazy:1;
-		u64 auto_enable:1;
-		u64 apic_vector:8;
-		u64 direct_mode:1;
-		u64 reserved_z0:3;
-		u64 sintx:4;
-		u64 reserved_z1:44;
-	} __packed;
-};
-
-
-/* Define the synthetic interrupt controller event flags format. */
-union hv_synic_event_flags {
-	unsigned long flags[HV_EVENT_FLAGS_LONG_COUNT];
-};
-
-/* Define SynIC control register. */
-union hv_synic_scontrol {
-	u64 as_uint64;
-	struct {
-		u64 enable:1;
-		u64 reserved:63;
-	} __packed;
-};
-
-/* Define synthetic interrupt source. */
-union hv_synic_sint {
-	u64 as_uint64;
-	struct {
-		u64 vector:8;
-		u64 reserved1:8;
-		u64 masked:1;
-		u64 auto_eoi:1;
-		u64 polling:1;
-		u64 reserved2:45;
-	} __packed;
-};
-
-/* Define the format of the SIMP register */
-union hv_synic_simp {
-	u64 as_uint64;
-	struct {
-		u64 simp_enabled:1;
-		u64 preserved:11;
-		u64 base_simp_gpa:52;
-	} __packed;
-};
-
-/* Define the format of the SIEFP register */
-union hv_synic_siefp {
-	u64 as_uint64;
-	struct {
-		u64 siefp_enabled:1;
-		u64 preserved:11;
-		u64 base_siefp_gpa:52;
-	} __packed;
-};
-
-struct hv_vpset {
-	u64 format;
-	u64 valid_bank_mask;
-	u64 bank_contents[];
-} __packed;
-
-/* HvCallSendSyntheticClusterIpi hypercall */
-struct hv_send_ipi {
-	u32 vector;
-	u32 reserved;
-	u64 cpu_mask;
-} __packed;
-
-/* HvCallSendSyntheticClusterIpiEx hypercall */
-struct hv_send_ipi_ex {
-	u32 vector;
-	u32 reserved;
-	struct hv_vpset vp_set;
-} __packed;
-
-/* HvFlushGuestPhysicalAddressSpace hypercalls */
-struct hv_guest_mapping_flush {
-	u64 address_space;
-	u64 flags;
-} __packed;
-
-/*
- *  HV_MAX_FLUSH_PAGES = "additional_pages" + 1. It's limited
- *  by the bitwidth of "additional_pages" in union hv_gpa_page_range.
- */
-#define HV_MAX_FLUSH_PAGES (2048)
-
-/* HvFlushGuestPhysicalAddressList hypercall */
-union hv_gpa_page_range {
-	u64 address_space;
-	struct {
-		u64 additional_pages:11;
-		u64 largepage:1;
-		u64 basepfn:52;
-	} page;
-};
-
-/*
- * All input flush parameters should be in single page. The max flush
- * count is equal with how many entries of union hv_gpa_page_range can
- * be populated into the input parameter page.
- */
-#define HV_MAX_FLUSH_REP_COUNT ((HV_HYP_PAGE_SIZE - 2 * sizeof(u64)) /	\
-				sizeof(union hv_gpa_page_range))
-
-struct hv_guest_mapping_flush_list {
-	u64 address_space;
-	u64 flags;
-	union hv_gpa_page_range gpa_list[HV_MAX_FLUSH_REP_COUNT];
-};
-
-/* HvFlushVirtualAddressSpace, HvFlushVirtualAddressList hypercalls */
-struct hv_tlb_flush {
-	u64 address_space;
-	u64 flags;
-	u64 processor_mask;
-	u64 gva_list[];
-} __packed;
-
-/* HvFlushVirtualAddressSpaceEx, HvFlushVirtualAddressListEx hypercalls */
-struct hv_tlb_flush_ex {
-	u64 address_space;
-	u64 flags;
-	struct hv_vpset hv_vp_set;
-	u64 gva_list[];
-} __packed;
-
 struct hv_partition_assist_pg {
 	u32 tlb_lock_count;
 };
 
-union hv_msi_entry {
-	u64 as_uint64;
-	struct {
-		u32 address;
-		u32 data;
-	} __packed;
-};
 
-struct hv_interrupt_entry {
-	u32 source;			/* 1 for MSI(-X) */
-	u32 reserved1;
-	union hv_msi_entry msi_entry;
-} __packed;
+#include <asm-generic/hyperv-tlfs.h>
 
-/*
- * flags for hv_device_interrupt_target.flags
- */
-#define HV_DEVICE_INTERRUPT_TARGET_MULTICAST		1
-#define HV_DEVICE_INTERRUPT_TARGET_PROCESSOR_SET	2
-
-struct hv_device_interrupt_target {
-	u32 vector;
-	u32 flags;
-	union {
-		u64 vp_mask;
-		struct hv_vpset vp_set;
-	};
-} __packed;
-
-/* HvRetargetDeviceInterrupt hypercall */
-struct hv_retarget_device_interrupt {
-	u64 partition_id;		/* use "self" */
-	u64 device_id;
-	struct hv_interrupt_entry int_entry;
-	u64 reserved2;
-	struct hv_device_interrupt_target int_target;
-} __packed __aligned(8);
 #endif

arch/x86/include/asm/kvm_host.h

···
 	u64 hv_crash_param[HV_X64_MSR_CRASH_PARAMS];
 	u64 hv_crash_ctl;
 
-	HV_REFERENCE_TSC_PAGE tsc_ref;
+	struct ms_hyperv_tsc_page tsc_ref;
 
 	struct idr conn_to_evt;
 

arch/x86/kvm/hyperv.c

···
  * These two equivalencies are implemented in this function.
  */
 static bool compute_tsc_page_parameters(struct pvclock_vcpu_time_info *hv_clock,
-					HV_REFERENCE_TSC_PAGE *tsc_ref)
+					struct ms_hyperv_tsc_page *tsc_ref)
 {
 	u64 max_mul;
 
···
 	u64 gfn;
 
 	BUILD_BUG_ON(sizeof(tsc_seq) != sizeof(hv->tsc_ref.tsc_sequence));
-	BUILD_BUG_ON(offsetof(HV_REFERENCE_TSC_PAGE, tsc_sequence) != 0);
+	BUILD_BUG_ON(offsetof(struct ms_hyperv_tsc_page, tsc_sequence) != 0);
 
 	if (!(hv->hv_tsc_page & HV_X64_MSR_TSC_REFERENCE_ENABLE))
 		return;

drivers/hv/channel.c

···
 EXPORT_SYMBOL_GPL(vmbus_send_tl_connect_request);
 
 /*
+ * Set/change the vCPU (@target_vp) the channel (@child_relid) will interrupt.
+ *
+ * CHANNELMSG_MODIFYCHANNEL messages are aynchronous.  Also, Hyper-V does not
+ * ACK such messages.  IOW we can't know when the host will stop interrupting
+ * the "old" vCPU and start interrupting the "new" vCPU for the given channel.
+ *
+ * The CHANNELMSG_MODIFYCHANNEL message type is supported since VMBus version
+ * VERSION_WIN10_V4_1.
+ */
+int vmbus_send_modifychannel(u32 child_relid, u32 target_vp)
+{
+	struct vmbus_channel_modifychannel conn_msg;
+	int ret;
+
+	memset(&conn_msg, 0, sizeof(conn_msg));
+	conn_msg.header.msgtype = CHANNELMSG_MODIFYCHANNEL;
+	conn_msg.child_relid = child_relid;
+	conn_msg.target_vp = target_vp;
+
+	ret = vmbus_post_msg(&conn_msg, sizeof(conn_msg), true);
+
+	trace_vmbus_send_modifychannel(&conn_msg, ret);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(vmbus_send_modifychannel);
+
+/*
  * create_gpadl_header - Creates a gpadl for the specified buffer
  */
 static int create_gpadl_header(void *kbuffer, u32 size,
···
 }
 EXPORT_SYMBOL_GPL(vmbus_teardown_gpadl);
 
-static void reset_channel_cb(void *arg)
-{
-	struct vmbus_channel *channel = arg;
-
-	channel->onchannel_callback = NULL;
-}
-
 void vmbus_reset_channel_cb(struct vmbus_channel *channel)
 {
+	unsigned long flags;
+
 	/*
 	 * vmbus_on_event(), running in the per-channel tasklet, can race
 	 * with vmbus_close_internal() in the case of SMP guest, e.g., when
 	 * the former is accessing channel->inbound.ring_buffer, the latter
 	 * could be freeing the ring_buffer pages, so here we must stop it
 	 * first.
+	 *
+	 * vmbus_chan_sched() might call the netvsc driver callback function
+	 * that ends up scheduling NAPI work that accesses the ring buffer.
+	 * At this point, we have to ensure that any such work is completed
+	 * and that the channel ring buffer is no longer being accessed, cf.
+	 * the calls to napi_disable() in netvsc_device_remove().
 	 */
 	tasklet_disable(&channel->callback_event);
 
-	channel->sc_creation_callback = NULL;
+	/* See the inline comments in vmbus_chan_sched(). */
+	spin_lock_irqsave(&channel->sched_lock, flags);
+	channel->onchannel_callback = NULL;
+	spin_unlock_irqrestore(&channel->sched_lock, flags);
 
-	/* Stop the callback asap */
-	if (channel->target_cpu != get_cpu()) {
-		put_cpu();
-		smp_call_function_single(channel->target_cpu, reset_channel_cb,
-					 channel, true);
-	} else {
-		reset_channel_cb(channel);
-		put_cpu();
-	}
+	channel->sc_creation_callback = NULL;
 
 	/* Re-enable tasklet for use on re-open */
 	tasklet_enable(&channel->callback_event);

drivers/hv/channel_mgmt.c

···
 #include <linux/module.h>
 #include <linux/completion.h>
 #include <linux/delay.h>
+#include <linux/cpu.h>
 #include <linux/hyperv.h>
 #include <asm/mshyperv.h>
 
 #include "hyperv_vmbus.h"
 
-static void init_vp_index(struct vmbus_channel *channel, u16 dev_type);
+static void init_vp_index(struct vmbus_channel *channel);
 
-static const struct vmbus_device vmbus_devs[] = {
+const struct vmbus_device vmbus_devs[] = {
 	/* IDE */
 	{ .dev_type = HV_IDE,
 	  HV_IDE_GUID,
···
 	if (!channel)
 		return NULL;
 
+	spin_lock_init(&channel->sched_lock);
 	spin_lock_init(&channel->lock);
 	init_completion(&channel->rescind_event);
 
 	INIT_LIST_HEAD(&channel->sc_list);
-	INIT_LIST_HEAD(&channel->percpu_list);
 
 	tasklet_init(&channel->callback_event,
 		     vmbus_on_event, (unsigned long)channel);
···
 	kobject_put(&channel->kobj);
 }
 
-static void percpu_channel_enq(void *arg)
+void vmbus_channel_map_relid(struct vmbus_channel *channel)
 {
-	struct vmbus_channel *channel = arg;
-	struct hv_per_cpu_context *hv_cpu
-		= this_cpu_ptr(hv_context.cpu_context);
-
-	list_add_tail_rcu(&channel->percpu_list, &hv_cpu->chan_list);
+	if (WARN_ON(channel->offermsg.child_relid >= MAX_CHANNEL_RELIDS))
+		return;
+	/*
+	 * The mapping of the channel's relid is visible from the CPUs that
+	 * execute vmbus_chan_sched() by the time that vmbus_chan_sched() will
+	 * execute:
+	 *
+	 *  (a) In the "normal (i.e., not resuming from hibernation)" path,
+	 *      the full barrier in smp_store_mb() guarantees that the store
+	 *      is propagated to all CPUs before the add_channel_work work
+	 *      is queued.  In turn, add_channel_work is queued before the
+	 *      channel's ring buffer is allocated/initialized and the
+	 *      OPENCHANNEL message for the channel is sent in vmbus_open().
+	 *      Hyper-V won't start sending the interrupts for the channel
+	 *      before the OPENCHANNEL message is acked.  The memory barrier
+	 *      in vmbus_chan_sched() -> sync_test_and_clear_bit() ensures
+	 *      that vmbus_chan_sched() must find the channel's relid in
+	 *      recv_int_page before retrieving the channel pointer from the
+	 *      array of channels.
+	 *
+	 *  (b) In the "resuming from hibernation" path, the smp_store_mb()
+	 *      guarantees that the store is propagated to all CPUs before
+	 *      the VMBus connection is marked as ready for the resume event
+	 *      (cf. check_ready_for_resume_event()).  The interrupt handler
+	 *      of the VMBus driver and vmbus_chan_sched() can not run before
+	 *      vmbus_bus_resume() has completed execution (cf. resume_noirq).
+	 */
+	smp_store_mb(
+		vmbus_connection.channels[channel->offermsg.child_relid],
+		channel);
 }
 
-static void percpu_channel_deq(void *arg)
+void vmbus_channel_unmap_relid(struct vmbus_channel *channel)
 {
-	struct vmbus_channel *channel = arg;
-
-	list_del_rcu(&channel->percpu_list);
+	if (WARN_ON(channel->offermsg.child_relid >= MAX_CHANNEL_RELIDS))
+		return;
+	WRITE_ONCE(
+		vmbus_connection.channels[channel->offermsg.child_relid],
+		NULL);
 }
-
 
 static void vmbus_release_relid(u32 relid)
 {
···
 
 void hv_process_channel_removal(struct vmbus_channel *channel)
 {
-	struct vmbus_channel *primary_channel;
 	unsigned long flags;
 
-	BUG_ON(!mutex_is_locked(&vmbus_connection.channel_mutex));
+	lockdep_assert_held(&vmbus_connection.channel_mutex);
 	BUG_ON(!channel->rescind);
 
-	if (channel->target_cpu != get_cpu()) {
-		put_cpu();
-		smp_call_function_single(channel->target_cpu,
-					 percpu_channel_deq, channel, true);
-	} else {
-		percpu_channel_deq(channel);
-		put_cpu();
-	}
+	/*
+	 * hv_process_channel_removal() could find INVALID_RELID only for
+	 * hv_sock channels.  See the inline comments in vmbus_onoffer().
+	 */
+	WARN_ON(channel->offermsg.child_relid == INVALID_RELID &&
+		!is_hvsock_channel(channel));
+
+	/*
+	 * Upon suspend, an in-use hv_sock channel is removed from the array of
+	 * channels and the relid is invalidated.  After hibernation, when the
+	 * user-space appplication destroys the channel, it's unnecessary and
+	 * unsafe to remove the channel from the array of channels.  See also
+	 * the inline comments before the call of vmbus_release_relid() below.
+	 */
+	if (channel->offermsg.child_relid != INVALID_RELID)
+		vmbus_channel_unmap_relid(channel);
 
 	if (channel->primary_channel == NULL) {
 		list_del(&channel->listentry);
-
-		primary_channel = channel;
 	} else {
-		primary_channel = channel->primary_channel;
+		struct vmbus_channel *primary_channel = channel->primary_channel;
 		spin_lock_irqsave(&primary_channel->lock, flags);
 		list_del(&channel->sc_list);
 		spin_unlock_irqrestore(&primary_channel->lock, flags);
 	}
 
 	/*
-	 * We need to free the bit for init_vp_index() to work in the case
-	 * of sub-channel, when we reload drivers like hv_netvsc.
+	 * If this is a "perf" channel, updates the hv_numa_map[] masks so that
+	 * init_vp_index() can (re-)use the CPU.
 	 */
-	if (channel->affinity_policy == HV_LOCALIZED)
-		cpumask_clear_cpu(channel->target_cpu,
-				  &primary_channel->alloced_cpus_in_node);
+	if (hv_is_perf_channel(channel))
+		hv_clear_alloced_cpu(channel->target_cpu);
 
 	/*
 	 * Upon suspend, an in-use hv_sock channel is marked as "rescinded" and
···
 		container_of(work, struct vmbus_channel, add_channel_work);
 	struct vmbus_channel *primary_channel = newchannel->primary_channel;
 	unsigned long flags;
-	u16 dev_type;
 	int ret;
-
-	dev_type = hv_get_dev_type(newchannel);
-
-	init_vp_index(newchannel, dev_type);
-
-	if (newchannel->target_cpu != get_cpu()) {
-		put_cpu();
-		smp_call_function_single(newchannel->target_cpu,
-					 percpu_channel_enq,
-					 newchannel, true);
-	} else {
-		percpu_channel_enq(newchannel);
-		put_cpu();
-	}
 
 	/*
 	 * This state is used to indicate a successful open
···
 	if (!newchannel->device_obj)
 		goto err_deq_chan;
 
-	newchannel->device_obj->device_id = dev_type;
+	newchannel->device_obj->device_id = newchannel->device_id;
 	/*
 	 * Add the new device to the bus. This will kick off device-driver
 	 * binding which eventually invokes the device driver's AddDevice()
···
 		spin_unlock_irqrestore(&primary_channel->lock, flags);
 	}
 
-	mutex_unlock(&vmbus_connection.channel_mutex);
+	/* vmbus_process_offer() has mapped the channel. */
+	vmbus_channel_unmap_relid(newchannel);
 
-	if (newchannel->target_cpu != get_cpu()) {
-		put_cpu();
-		smp_call_function_single(newchannel->target_cpu,
-					 percpu_channel_deq,
-					 newchannel, true);
-	} else {
-		percpu_channel_deq(newchannel);
-		put_cpu();
-	}
+	mutex_unlock(&vmbus_connection.channel_mutex);
 
 	vmbus_release_relid(newchannel->offermsg.child_relid);
 
···
 	unsigned long flags;
 	bool fnew = true;
 
+	/*
+	 * Synchronize vmbus_process_offer() and CPU hotplugging:
+	 *
+	 * CPU1				CPU2
+	 *
+	 * [vmbus_process_offer()]	[Hot removal of the CPU]
+	 *
+	 * CPU_READ_LOCK		CPUS_WRITE_LOCK
+	 * LOAD cpu_online_mask		SEARCH chn_list
+	 * STORE target_cpu		LOAD target_cpu
+	 * INSERT chn_list		STORE cpu_online_mask
+	 * CPUS_READ_UNLOCK		CPUS_WRITE_UNLOCK
+	 *
+	 * Forbids: CPU1's LOAD from *not* seing CPU2's STORE &&
+	 * 		CPU2's SEARCH from *not* seeing CPU1's INSERT
+	 *
+	 * Forbids: CPU2's SEARCH from seeing CPU1's INSERT &&
+	 * 		CPU2's LOAD from *not* seing CPU1's STORE
+	 */
+	cpus_read_lock();
+
+	/*
+	 * Serializes the modifications of the chn_list list as well as
+	 * the accesses to next_numa_node_id in init_vp_index().
+	 */
 	mutex_lock(&vmbus_connection.channel_mutex);
+
+	init_vp_index(newchannel);
 
 	/* Remember the channels that should be cleaned up upon suspend. */
 	if (is_hvsock_channel(newchannel) || is_sub_channel(newchannel))
···
 		spin_unlock_irqrestore(&channel->lock, flags);
 	}
 
+	vmbus_channel_map_relid(newchannel);
+
 	mutex_unlock(&vmbus_connection.channel_mutex);
+	cpus_read_unlock();
 
 	/*
 	 * vmbus_process_offer() mustn't call channel->sc_creation_callback()
···
  * We use this state to statically distribute the channel interrupt load.
  */
 static int next_numa_node_id;
-/*
- * init_vp_index() accesses global variables like next_numa_node_id, and
- * it can run concurrently for primary channels and sub-channels: see
- * vmbus_process_offer(), so we need the lock to protect the global
- * variables.
- */
-static DEFINE_SPINLOCK(bind_channel_to_cpu_lock);
 
 /*
  * Starting with Win8, we can statically distribute the incoming
  * channel interrupt load by binding a channel to VCPU.
- * We distribute the interrupt loads to one or more NUMA nodes based on
- * the channel's affinity_policy.
  *
  * For pre-win8 hosts or non-performance critical channels we assign the
- * first CPU in the first NUMA node.
+ * VMBUS_CONNECT_CPU.
+ *
+ * Starting with win8, performance critical channels will be distributed
+ * evenly among all the available NUMA nodes.  Once the node is assigned,
+ * we will assign the CPU based on a simple round robin scheme.
  */
-static void init_vp_index(struct vmbus_channel *channel, u16 dev_type)
+static void init_vp_index(struct vmbus_channel *channel)
 {
-	u32 cur_cpu;
-	bool perf_chn = vmbus_devs[dev_type].perf_device;
-	struct vmbus_channel *primary = channel->primary_channel;
-	int next_node;
+	bool perf_chn = hv_is_perf_channel(channel);
 	cpumask_var_t available_mask;
 	struct cpumask *alloced_mask;
+	u32 target_cpu;
+	int numa_node;
 
 	if ((vmbus_proto_version == VERSION_WS2008) ||
 	    (vmbus_proto_version == VERSION_WIN7) || (!perf_chn) ||
 	    !alloc_cpumask_var(&available_mask, GFP_KERNEL)) {
 		/*
 		 * Prior to win8, all channel interrupts are
-		 * delivered on cpu 0.
+		 * delivered on VMBUS_CONNECT_CPU.
 		 * Also if the channel is not a performance critical
-		 * channel, bind it to cpu 0.
-		 * In case alloc_cpumask_var() fails, bind it to cpu 0.
+		 * channel, bind it to VMBUS_CONNECT_CPU.
+		 * In case alloc_cpumask_var() fails, bind it to
+		 * VMBUS_CONNECT_CPU.
 		 */
-		channel->numa_node = 0;
-		channel->target_cpu = 0;
-		channel->target_vp = hv_cpu_number_to_vp_number(0);
+		channel->numa_node = cpu_to_node(VMBUS_CONNECT_CPU);
+		channel->target_cpu = VMBUS_CONNECT_CPU;
+		channel->target_vp =
+			hv_cpu_number_to_vp_number(VMBUS_CONNECT_CPU);
+		if (perf_chn)
+			hv_set_alloced_cpu(VMBUS_CONNECT_CPU);
 		return;
 	}
 
-	spin_lock(&bind_channel_to_cpu_lock);
-
-	/*
-	 * Based on the channel affinity policy, we will assign the NUMA
-	 * nodes.
-	 */
-
-	if ((channel->affinity_policy == HV_BALANCED) || (!primary)) {
-		while (true) {
-			next_node = next_numa_node_id++;
-			if (next_node == nr_node_ids) {
-				next_node = next_numa_node_id = 0;
-				continue;
-			}
-			if (cpumask_empty(cpumask_of_node(next_node)))
-				continue;
-			break;
+	while (true) {
+		numa_node = next_numa_node_id++;
+		if (numa_node == nr_node_ids) {
+			next_numa_node_id = 0;
+			continue;
 		}
-		channel->numa_node = next_node;
-		primary = channel;
+		if (cpumask_empty(cpumask_of_node(numa_node)))
+			continue;
+		break;
 	}
-	alloced_mask = &hv_context.hv_numa_map[primary->numa_node];
+	channel->numa_node = numa_node;
+	alloced_mask = &hv_context.hv_numa_map[numa_node];
 
 	if (cpumask_weight(alloced_mask) ==
-	    cpumask_weight(cpumask_of_node(primary->numa_node))) {
+	    cpumask_weight(cpumask_of_node(numa_node))) {
 		/*
 		 * We have cycled through all the CPUs in the node;
 		 * reset the alloced map.
···
 		cpumask_clear(alloced_mask);
 	}
 
-	cpumask_xor(available_mask, alloced_mask,
-		    cpumask_of_node(primary->numa_node));
+	cpumask_xor(available_mask, alloced_mask, cpumask_of_node(numa_node));
 
-	cur_cpu = -1;
+	target_cpu = cpumask_first(available_mask);
+	cpumask_set_cpu(target_cpu, alloced_mask);
 
-	if (primary->affinity_policy == HV_LOCALIZED) {
-		/*
-		 * Normally Hyper-V host doesn't create more subchannels
-		 * than there are VCPUs on the node but it is possible when not
-		 * all present VCPUs on the node are initialized by guest.
-		 * Clear the alloced_cpus_in_node to start over.
-		 */
-		if (cpumask_equal(&primary->alloced_cpus_in_node,
-				  cpumask_of_node(primary->numa_node)))
-			cpumask_clear(&primary->alloced_cpus_in_node);
-	}
-
-	while (true) {
-		cur_cpu = cpumask_next(cur_cpu, available_mask);
-		if (cur_cpu >= nr_cpu_ids) {
-			cur_cpu = -1;
-			cpumask_copy(available_mask,
-				     cpumask_of_node(primary->numa_node));
-			continue;
-		}
-
-		if (primary->affinity_policy == HV_LOCALIZED) {
-			/*
-			 * NOTE: in the case of sub-channel, we clear the
-			 * sub-channel related bit(s) in
-			 * primary->alloced_cpus_in_node in
-			 * hv_process_channel_removal(), so when we
-			 * reload drivers like hv_netvsc in SMP guest, here
-			 * we're able to re-allocate
-			 * bit from primary->alloced_cpus_in_node.
-			 */
-			if (!cpumask_test_cpu(cur_cpu,
-					      &primary->alloced_cpus_in_node)) {
-				cpumask_set_cpu(cur_cpu,
-						&primary->alloced_cpus_in_node);
-				cpumask_set_cpu(cur_cpu, alloced_mask);
-				break;
-			}
-		} else {
-			cpumask_set_cpu(cur_cpu, alloced_mask);
-			break;
-		}
-	}
-
-	channel->target_cpu = cur_cpu;
-	channel->target_vp = hv_cpu_number_to_vp_number(cur_cpu);
-
-	spin_unlock(&bind_channel_to_cpu_lock);
+	channel->target_cpu = target_cpu;
+	channel->target_vp = hv_cpu_number_to_vp_number(target_cpu);
 
 	free_cpumask_var(available_mask);
 }
···
 	       sizeof(struct vmbus_channel_offer_channel));
 	channel->monitor_grp = (u8)offer->monitorid / 32;
 	channel->monitor_bit = (u8)offer->monitorid % 32;
+	channel->device_id = hv_get_dev_type(channel);
 }
 
 /*
···
 	oldchannel = find_primary_channel_by_offer(offer);
 
 	if (oldchannel != NULL) {
-		atomic_dec(&vmbus_connection.offer_in_progress);
-
 		/*
 		 * We're resuming from hibernation: all the sub-channel and
 		 * hv_sock channels we had before the hibernation should have
···
 		 * primary channel that we had before the hibernation.
 		 */
 
+		/*
+		 * { Initially: channel relid = INVALID_RELID,
+		 *		channels[valid_relid] = NULL }
+		 *
+		 * CPU1					CPU2
+		 *
+		 * [vmbus_onoffer()]			[vmbus_device_release()]
+		 *
+		 * LOCK channel_mutex			LOCK channel_mutex
+		 * STORE channel relid = valid_relid	LOAD r1 = channel relid
+		 * MAP_RELID channel			if (r1 != INVALID_RELID)
+		 * UNLOCK channel_mutex			  UNMAP_RELID channel
+		 *					UNLOCK channel_mutex
+		 *
+		 * Forbids: r1 == valid_relid &&
+		 * 		channels[valid_relid] == channel
+		 *
+		 * Note.  r1 can be INVALID_RELID only for an hv_sock channel.
+		 * None of the hv_sock channels which were present before the
+		 * suspend are re-offered upon the resume.  See the WARN_ON()
+		 * in hv_process_channel_removal().
+		 */
+		mutex_lock(&vmbus_connection.channel_mutex);
+
+		atomic_dec(&vmbus_connection.offer_in_progress);
+
 		WARN_ON(oldchannel->offermsg.child_relid != INVALID_RELID);
 		/* Fix up the relid. */
 		oldchannel->offermsg.child_relid = offer->child_relid;
 
 		offer_sz = sizeof(*offer);
-		if (memcmp(offer, &oldchannel->offermsg, offer_sz) == 0) {
-			check_ready_for_resume_event();
-			return;
+		if (memcmp(offer, &oldchannel->offermsg, offer_sz) != 0) {
+			/*
+			 * This is not an error, since the host can also change
+			 * the other field(s) of the offer, e.g. on WS RS5
+			 * (Build 17763), the offer->connection_id of the
+			 * Mellanox VF vmbus device can change when the host
+			 * reoffers the device upon resume.
+			 */
+			pr_debug("vmbus offer changed: relid=%d\n",
+				 offer->child_relid);
+
+			print_hex_dump_debug("Old vmbus offer: ",
+					     DUMP_PREFIX_OFFSET, 16, 4,
+					     &oldchannel->offermsg, offer_sz,
+					     false);
+			print_hex_dump_debug("New vmbus offer: ",
+					     DUMP_PREFIX_OFFSET, 16, 4,
+					     offer, offer_sz, false);
+
+			/* Fix up the old channel. */
+			vmbus_setup_channel_state(oldchannel, offer);
 		}
 
-		/*
-		 * This is not an error, since the host can also change the
-		 * other field(s) of the offer, e.g. on WS RS5 (Build 17763),
-		 * the offer->connection_id of the Mellanox VF vmbus device
-		 * can change when the host reoffers the device upon resume.
-		 */
-		pr_debug("vmbus offer changed: relid=%d\n",
-			 offer->child_relid);
-
-		print_hex_dump_debug("Old vmbus offer: ", DUMP_PREFIX_OFFSET,
-				     16, 4, &oldchannel->offermsg, offer_sz,
-				     false);
-		print_hex_dump_debug("New vmbus offer: ", DUMP_PREFIX_OFFSET,
-				     16, 4, offer, offer_sz, false);
-
-		/* Fix up the old channel. */
-		vmbus_setup_channel_state(oldchannel, offer);
-
+		/* Add the channel back to the array of channels. */
+		vmbus_channel_map_relid(oldchannel);
 		check_ready_for_resume_event();
 
+		mutex_unlock(&vmbus_connection.channel_mutex);
 		return;
 	}
 
···
 	 * offer comes in first and then the rescind.
 	 * Since we process these events in work elements,
 	 * and with preemption, we may end up processing
-	 * the events out of order. Given that we handle these
-	 * work elements on the same CPU, this is possible only
-	 * in the case of preemption. In any case wait here
-	 * until the offer processing has moved beyond the
-	 * point where the channel is discoverable.
+	 * the events out of order.  We rely on the synchronization
+	 * provided by offer_in_progress and by channel_mutex for
+	 * ordering these events:
+	 *
+	 * { Initially: offer_in_progress = 1 }
+	 *
+	 * CPU1				CPU2
+	 *
+	 * [vmbus_onoffer()]		[vmbus_onoffer_rescind()]
+	 *
+	 * LOCK channel_mutex		WAIT_ON offer_in_progress == 0
+	 * DECREMENT offer_in_progress	LOCK channel_mutex
+	 * STORE channels[]		LOAD channels[]
+	 * UNLOCK channel_mutex		UNLOCK channel_mutex
+	 *
+	 * Forbids: CPU2's LOAD from *not* seeing CPU1's STORE
 	 */
 
 	while (atomic_read(&vmbus_connection.offer_in_progress) != 0) {
···
 /* Channel message dispatch table */
 const struct vmbus_channel_message_table_entry
 channel_message_table[CHANNELMSG_COUNT] = {
-	{ CHANNELMSG_INVALID,			0, NULL },
-	{ CHANNELMSG_OFFERCHANNEL,		0, vmbus_onoffer },
-	{ CHANNELMSG_RESCIND_CHANNELOFFER,	0, vmbus_onoffer_rescind },
-	{ CHANNELMSG_REQUESTOFFERS,		0, NULL },
-	{ CHANNELMSG_ALLOFFERS_DELIVERED,	1, vmbus_onoffers_delivered },
-	{ CHANNELMSG_OPENCHANNEL,		0, NULL },
-	{ CHANNELMSG_OPENCHANNEL_RESULT,	1, vmbus_onopen_result },
-	{ CHANNELMSG_CLOSECHANNEL,		0, NULL },
-	{ CHANNELMSG_GPADL_HEADER,		0, NULL },
-	{ CHANNELMSG_GPADL_BODY,		0, NULL },
-	{ CHANNELMSG_GPADL_CREATED,		1, vmbus_ongpadl_created },
-	{ CHANNELMSG_GPADL_TEARDOWN,		0, NULL },
-	{ CHANNELMSG_GPADL_TORNDOWN,		1, vmbus_ongpadl_torndown },
-	{ CHANNELMSG_RELID_RELEASED,		0, NULL },
-	{ CHANNELMSG_INITIATE_CONTACT,		0, NULL },
-	{ CHANNELMSG_VERSION_RESPONSE,		1, vmbus_onversion_response },
-	{ CHANNELMSG_UNLOAD,			0, NULL },
-	{ CHANNELMSG_UNLOAD_RESPONSE,		1, vmbus_unload_response },
-	{ CHANNELMSG_18,			0, NULL },
-	{ CHANNELMSG_19,			0, NULL },
-	{ CHANNELMSG_20,			0, NULL },
-	{ CHANNELMSG_TL_CONNECT_REQUEST,	0, NULL },
-	{ CHANNELMSG_22,			0, NULL },
-	{ CHANNELMSG_TL_CONNECT_RESULT,		0, NULL },
+	{ CHANNELMSG_INVALID,			0, NULL, 0},
+	{ CHANNELMSG_OFFERCHANNEL,		0, vmbus_onoffer,
+		sizeof(struct vmbus_channel_offer_channel)},
+	{ CHANNELMSG_RESCIND_CHANNELOFFER,	0, vmbus_onoffer_rescind,
+		sizeof(struct vmbus_channel_rescind_offer) },
+	{ CHANNELMSG_REQUESTOFFERS,		0, NULL, 0},
+	{ CHANNELMSG_ALLOFFERS_DELIVERED,	1, vmbus_onoffers_delivered, 0},
+	{ CHANNELMSG_OPENCHANNEL,		0, NULL, 0},
+	{ CHANNELMSG_OPENCHANNEL_RESULT,	1, vmbus_onopen_result,
+		sizeof(struct vmbus_channel_open_result)},
+	{ CHANNELMSG_CLOSECHANNEL,		0, NULL, 0},
+	{ CHANNELMSG_GPADL_HEADER,		0, NULL, 0},
+	{ CHANNELMSG_GPADL_BODY,		0, NULL, 0},
+	{ CHANNELMSG_GPADL_CREATED,		1, vmbus_ongpadl_created,
+		sizeof(struct vmbus_channel_gpadl_created)},
+	{ CHANNELMSG_GPADL_TEARDOWN,		0, NULL, 0},
+	{ CHANNELMSG_GPADL_TORNDOWN,		1, vmbus_ongpadl_torndown,
+		sizeof(struct vmbus_channel_gpadl_torndown) },
+	{ CHANNELMSG_RELID_RELEASED,		0, NULL, 0},
+	{ CHANNELMSG_INITIATE_CONTACT,		0, NULL, 0},
+	{ CHANNELMSG_VERSION_RESPONSE,		1, vmbus_onversion_response,
+		sizeof(struct vmbus_channel_version_response)},
+	{ CHANNELMSG_UNLOAD,			0, NULL, 0},
+	{ CHANNELMSG_UNLOAD_RESPONSE,		1, vmbus_unload_response, 0},
+	{ CHANNELMSG_18,			0, NULL, 0},
+	{ CHANNELMSG_19,			0, NULL, 0},
+	{ CHANNELMSG_20,			0, NULL, 0},
+	{ CHANNELMSG_TL_CONNECT_REQUEST,	0, NULL, 0},
+	{ CHANNELMSG_MODIFYCHANNEL,		0, NULL, 0},
+	{ CHANNELMSG_TL_CONNECT_RESULT,		0, NULL, 0},
 };
 
 /*
···
  *
  * This is invoked in the vmbus worker thread context.
  */
-void vmbus_onmessage(void *context)
+void vmbus_onmessage(struct vmbus_channel_message_header *hdr)
 {
-	struct hv_message *msg = context;
-	struct vmbus_channel_message_header *hdr;
-
-	hdr = (struct vmbus_channel_message_header *)msg->u.payload;
-
 	trace_vmbus_on_message(hdr);
 
 	/*

drivers/hv/connection.c

···
 int vmbus_negotiate_version(struct vmbus_channel_msginfo *msginfo, u32 version)
 {
 	int ret = 0;
-	unsigned int cur_cpu;
 	struct vmbus_channel_initiate_contact *msg;
 	unsigned long flags;
 
···
 
 	msg->monitor_page1 = virt_to_phys(vmbus_connection.monitor_pages[0]);
 	msg->monitor_page2 = virt_to_phys(vmbus_connection.monitor_pages[1]);
-	/*
-	 * We want all channel messages to be delivered on CPU 0.
-	 * This has been the behavior pre-win8. This is not
-	 * perf issue and having all channel messages delivered on CPU 0
-	 * would be ok.
-	 * For post win8 hosts, we support receiving channel messagges on
-	 * all the CPUs. This is needed for kexec to work correctly where
-	 * the CPU attempting to connect may not be CPU 0.
-	 */
-	if (version >= VERSION_WIN8_1) {
-		cur_cpu = get_cpu();
-		msg->target_vcpu = hv_cpu_number_to_vp_number(cur_cpu);
-		vmbus_connection.connect_cpu = cur_cpu;
-		put_cpu();
-	} else {
-		msg->target_vcpu = 0;
-		vmbus_connection.connect_cpu = 0;
-	}
+	msg->target_vcpu = hv_cpu_number_to_vp_number(VMBUS_CONNECT_CPU);
 
 	/*
 	 * Add to list before we send the request since we may
···
 	pr_info("Vmbus version:%d.%d\n",
 		version >> 16, version & 0xFFFF);
 
+	vmbus_connection.channels = kcalloc(MAX_CHANNEL_RELIDS,
+					    sizeof(struct vmbus_channel *),
+					    GFP_KERNEL);
+	if (vmbus_connection.channels == NULL) {
+		ret = -ENOMEM;
+		goto cleanup;
+	}
+
 	kfree(msginfo);
 	return 0;
 
···
  */
 struct vmbus_channel *relid2channel(u32 relid)
 {
-	struct vmbus_channel *channel;
-	struct vmbus_channel *found_channel  = NULL;
-	struct list_head *cur, *tmp;
-	struct vmbus_channel *cur_sc;
-
-	BUG_ON(!mutex_is_locked(&vmbus_connection.channel_mutex));
-
-	list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
-		if (channel->offermsg.child_relid == relid) {
-			found_channel = channel;
-			break;
-		} else if (!list_empty(&channel->sc_list)) {
-			/*
-			 * Deal with sub-channels.
-			 */
-			list_for_each_safe(cur, tmp, &channel->sc_list) {
-				cur_sc = list_entry(cur, struct vmbus_channel,
-							sc_list);
-				if (cur_sc->offermsg.child_relid == relid) {
-					found_channel = cur_sc;
-					break;
-				}
-			}
-		}
-	}
-
-	return found_channel;
+	if (WARN_ON(relid >= MAX_CHANNEL_RELIDS))
+		return NULL;
+	return READ_ONCE(vmbus_connection.channels[relid]);
 }
 
 /*

drivers/hv/hv.c

···
 			pr_err("Unable to allocate post msg page\n");
 			goto err;
 		}
-
-		INIT_LIST_HEAD(&hv_cpu->chan_list);
 	}
 
 	return 0;
···
 	unsigned long flags;
 
 	/*
+	 * Hyper-V does not provide a way to change the connect CPU once
+	 * it is set; we must prevent the connect CPU from going offline.
+	 */
+	if (cpu == VMBUS_CONNECT_CPU)
+		return -EBUSY;
+
+	/*
 	 * Search for channels which are bound to the CPU we're about to
-	 * cleanup. In case we find one and vmbus is still connected we need to
-	 * fail, this will effectively prevent CPU offlining. There is no way
-	 * we can re-bind channels to different CPUs for now.
+	 * cleanup.  In case we find one and vmbus is still connected, we
+	 * fail; this will effectively prevent CPU offlining.
+	 *
+	 * TODO: Re-bind the channels to different CPUs.
 	 */
 	mutex_lock(&vmbus_connection.channel_mutex);
 	list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {

drivers/hv/hv_fcopy.c

···
 {
 	/* Transaction is finished, reset the state here to avoid races. */
 	fcopy_transaction.state = HVUTIL_READY;
-	hv_fcopy_onchannelcallback(channel);
+	tasklet_schedule(&((struct vmbus_channel *)channel)->callback_event);
 }
 
 static void fcopy_timeout_func(struct work_struct *dummy)

drivers/hv/hv_snapshot.c

···
 {
 	/* Transaction is finished, reset the state here to avoid races. */
 	vss_transaction.state = HVUTIL_READY;
-	hv_vss_onchannelcallback(channel);
+	tasklet_schedule(&((struct vmbus_channel *)channel)->callback_event);
 }
 
 /*

drivers/hv/hv_trace.h

···
 			   __entry->monitorid = offer->monitorid;
 			   __entry->is_ddc_int = offer->is_dedicated_interrupt;
 			   __entry->connection_id = offer->connection_id;
-			   memcpy(__entry->if_type,
-				  &offer->offer.if_type.b, 16);
-			   memcpy(__entry->if_instance,
-				  &offer->offer.if_instance.b, 16);
+			   export_guid(__entry->if_type, &offer->offer.if_type);
+			   export_guid(__entry->if_instance, &offer->offer.if_instance);
 			   __entry->chn_flags = offer->offer.chn_flags;
 			   __entry->mmio_mb = offer->offer.mmio_megabytes;
 			   __entry->sub_idx = offer->offer.sub_channel_index;
···
 	    TP_printk("sending guest_endpoint_id %pUl, host_service_id %pUl, "
 		      "ret %d",
 		      __entry->guest_id, __entry->host_id, __entry->ret
+		    )
+	);
+
+TRACE_EVENT(vmbus_send_modifychannel,
+	    TP_PROTO(const struct vmbus_channel_modifychannel *msg,
+		     int ret),
+	    TP_ARGS(msg, ret),
+	    TP_STRUCT__entry(
+		    __field(u32, child_relid)
+		    __field(u32, target_vp)
+		    __field(int, ret)
+		    ),
+	    TP_fast_assign(
+		    __entry->child_relid = msg->child_relid;
+		    __entry->target_vp = msg->target_vp;
+		    __entry->ret = ret;
+		    ),
+	    TP_printk("binding child_relid 0x%x to target_vp 0x%x, ret %d",
+		      __entry->child_relid, __entry->target_vp, __entry->ret
 		    )
 	);
 

drivers/hv/hyperv_vmbus.h

···
 	 * basis.
 	 */
 	struct tasklet_struct msg_dpc;
-
-	/*
-	 * To optimize the mapping of relid to channel, maintain
-	 * per-cpu list of the channels based on their CPU affinity.
-	 */
-	struct list_head chan_list;
 };
 
 struct hv_context {
···
 /* TODO: Need to make this configurable */
 #define MAX_NUM_CHANNELS_SUPPORTED	256
 
+#define MAX_CHANNEL_RELIDS					\
+	max(MAX_NUM_CHANNELS_SUPPORTED, HV_EVENT_FLAGS_COUNT)
 
 enum vmbus_connect_state {
 	DISCONNECTED,
···
 
 #define MAX_SIZE_CHANNEL_MESSAGE	HV_MESSAGE_PAYLOAD_BYTE_COUNT
 
-struct vmbus_connection {
-	/*
-	 * CPU on which the initial host contact was made.
-	 */
-	int connect_cpu;
+/*
+ * The CPU that Hyper-V will interrupt for VMBUS messages, such as
+ * CHANNELMSG_OFFERCHANNEL and CHANNELMSG_RESCIND_CHANNELOFFER.
+ */
+#define VMBUS_CONNECT_CPU	0
 
+struct vmbus_connection {
 	u32 msg_conn_id;
 
 	atomic_t offer_in_progress;
···
 	/* List of channels */
 	struct list_head chn_list;
 	struct mutex channel_mutex;
+
+	/* Array of channels */
+	struct vmbus_channel **channels;
 
 	/*
 	 * An offer message is handled first on the work_queue, and then
···
 	enum vmbus_channel_message_type message_type;
 	enum vmbus_message_handler_type handler_type;
 	void (*message_handler)(struct vmbus_channel_message_header *msg);
+	u32 min_payload_len;
 };
 
 extern const struct vmbus_channel_message_table_entry
···
 			   struct vmbus_channel *channel);
 
 void vmbus_remove_channel_attr_group(struct vmbus_channel *channel);
+
+void vmbus_channel_map_relid(struct vmbus_channel *channel);
+void vmbus_channel_unmap_relid(struct vmbus_channel *channel);
 
 struct vmbus_channel *relid2channel(u32 relid);
 
···
 {
 	if (!channel)
 		return;
-
-	if (in_interrupt() && (channel->target_cpu == smp_processor_id())) {
-		cb(channel);
-		return;
-	}
-	smp_call_function_single(channel->target_cpu, cb, channel, true);
+	cb(channel);
 }
 
 enum hvutil_device_state {
···
 	INTERRUPT_DELAY = 0,
 	MESSAGE_DELAY   = 1,
 };
+
+extern const struct vmbus_device vmbus_devs[];
+
+static inline bool hv_is_perf_channel(struct vmbus_channel *channel)
+{
+	return vmbus_devs[channel->device_id].perf_device;
+}
+
+static inline bool hv_is_alloced_cpu(unsigned int cpu)
+{
+	struct vmbus_channel *channel, *sc;
+
+	lockdep_assert_held(&vmbus_connection.channel_mutex);
+	/*
+	 * List additions/deletions as well as updates of the target CPUs are
+	 * protected by channel_mutex.
+	 */
+	list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
+		if (!hv_is_perf_channel(channel))
+			continue;
+		if (channel->target_cpu == cpu)
+			return true;
+		list_for_each_entry(sc, &channel->sc_list, sc_list) {
+			if (sc->target_cpu == cpu)
+				return true;
+		}
+	}
+	return false;
+}
+
+static inline void hv_set_alloced_cpu(unsigned int cpu)
+{
+	cpumask_set_cpu(cpu, &hv_context.hv_numa_map[cpu_to_node(cpu)]);
+}
+
+static inline void hv_clear_alloced_cpu(unsigned int cpu)
+{
+	if (hv_is_alloced_cpu(cpu))
+		return;
+	cpumask_clear_cpu(cpu, &hv_context.hv_numa_map[cpu_to_node(cpu)]);
+}
+
+static inline void hv_update_alloced_cpus(unsigned int old_cpu,
+					  unsigned int new_cpu)
+{
+	hv_set_alloced_cpu(new_cpu);
+	hv_clear_alloced_cpu(old_cpu);
+}
 
 #ifdef CONFIG_HYPERV_TESTING
 

drivers/hv/vmbus_drv.c

···
 	return 0;
 }
 
-#define VMBUS_ALIAS_LEN ((sizeof((struct hv_vmbus_device_id *)0)->guid) * 2)
-static void print_alias_name(struct hv_device *hv_dev, char *alias_name)
-{
-	int i;
-	for (i = 0; i < VMBUS_ALIAS_LEN; i += 2)
-		sprintf(&alias_name[i], "%02x", hv_dev->dev_type.b[i/2]);
-}
-
 static u8 channel_monitor_group(const struct vmbus_channel *channel)
 {
 	return (u8)channel->offermsg.monitorid / 32;
···
 	if (!hv_dev->channel)
 		return -ENODEV;
 	return sprintf(buf, "{%pUl}\n",
-		       hv_dev->channel->offermsg.offer.if_type.b);
+		       &hv_dev->channel->offermsg.offer.if_type);
 }
 static DEVICE_ATTR_RO(class_id);
 
···
 	if (!hv_dev->channel)
 		return -ENODEV;
 	return sprintf(buf, "{%pUl}\n",
-		       hv_dev->channel->offermsg.offer.if_instance.b);
+		       &hv_dev->channel->offermsg.offer.if_instance);
 }
 static DEVICE_ATTR_RO(device_id);
 
···
 			     struct device_attribute *dev_attr, char *buf)
 {
 	struct hv_device *hv_dev = device_to_hv_device(dev);
-	char alias_name[VMBUS_ALIAS_LEN + 1];
 
-	print_alias_name(hv_dev, alias_name);
-	return sprintf(buf, "vmbus:%s\n", alias_name);
+	return sprintf(buf, "vmbus:%*phN\n", UUID_SIZE, &hv_dev->dev_type);
 }
 static DEVICE_ATTR_RO(modalias);
 
···
 static int vmbus_uevent(struct device *device, struct kobj_uevent_env *env)
 {
 	struct hv_device *dev = device_to_hv_device(device);
-	int ret;
-	char alias_name[VMBUS_ALIAS_LEN + 1];
+	const char *format = "MODALIAS=vmbus:%*phN";
 
-	print_alias_name(dev, alias_name);
-	ret = add_uevent_var(env, "MODALIAS=vmbus:%s", alias_name);
-	return ret;
+	return add_uevent_var(env, format, UUID_SIZE, &dev->dev_type);
 }
 
 static const struct hv_vmbus_device_id *
···
 
 struct onmessage_work_context {
 	struct work_struct work;
-	struct hv_message msg;
+	struct {
+		struct hv_message_header header;
+		u8 payload[];
+	} msg;
 };
 
 static void vmbus_onmessage_work(struct work_struct *work)
···
 
 	ctx = container_of(work, struct onmessage_work_context,
 			   work);
-	vmbus_onmessage(&ctx->msg);
+	vmbus_onmessage((struct vmbus_channel_message_header *)
+			&ctx->msg.payload);
 	kfree(ctx);
 }
 
···
 	struct onmessage_work_context *ctx;
 	u32 message_type = msg->header.message_type;
 
+	/*
+	 * 'enum vmbus_channel_message_type' is supposed to always be 'u32' as
+	 * it is being used in 'struct vmbus_channel_message_header' definition
+	 * which is supposed to match hypervisor ABI.
+	 */
+	BUILD_BUG_ON(sizeof(enum vmbus_channel_message_type) != sizeof(u32));
+
 	if (message_type == HVMSG_NONE)
 		/* no msg */
 		return;
···
 		goto msg_handled;
 	}
 
+	if (msg->header.payload_size > HV_MESSAGE_PAYLOAD_BYTE_COUNT) {
+		WARN_ONCE(1, "payload size is too large (%d)\n",
+			  msg->header.payload_size);
+		goto msg_handled;
+	}
+
 	entry = &channel_message_table[hdr->msgtype];
 
 	if (!entry->message_handler)
 		goto msg_handled;
 
+	if (msg->header.payload_size < entry->min_payload_len) {
+		WARN_ONCE(1, "message too short: msgtype=%d len=%d\n",
+			  hdr->msgtype, msg->header.payload_size);
+		goto msg_handled;
+	}
+
 	if (entry->handler_type	== VMHT_BLOCKING) {
-		ctx = kmalloc(sizeof(*ctx), GFP_ATOMIC);
+		ctx = kmalloc(sizeof(*ctx) + msg->header.payload_size,
+			      GFP_ATOMIC);
 		if (ctx == NULL)
 			return;
 
 		INIT_WORK(&ctx->work, vmbus_onmessage_work);
-		memcpy(&ctx->msg, msg, sizeof(*msg));
+		memcpy(&ctx->msg, msg, sizeof(msg->header) +
+		       msg->header.payload_size);
 
 		/*
 		 * The host can generate a rescind message while we
 		 * may still be handling the original offer. We deal with
-		 * this condition by ensuring the processing is done on the
-		 * same CPU.
+		 * this condition by relying on the synchronization provided
+		 * by offer_in_progress and by channel_mutex.  See also the
+		 * inline comments in vmbus_onoffer_rescind().
 		 */
 		switch (hdr->msgtype) {
 		case CHANNELMSG_RESCIND_CHANNELOFFER:
 			/*
 			 * If we are handling the rescind message;
 			 * schedule the work on the global work queue.
+			 *
+			 * The OFFER message and the RESCIND message should
+			 * not be handled by the same serialized work queue,
+			 * because the OFFER handler may call vmbus_open(),
+			 * which tries to open the channel by sending an
+			 * OPEN_CHANNEL message to the host and waits for
+			 * the host's response; however, if the host has
+			 * rescinded the channel before it receives the
+			 * OPEN_CHANNEL message, the host just silently
+			 * ignores the OPEN_CHANNEL message; as a result,
+			 * the guest's OFFER handler hangs for ever, if we
+			 * handle the RESCIND message in the same serialized
+			 * work queue: the RESCIND handler can not start to
+			 * run before the OFFER handler finishes.
 			 */
-			schedule_work_on(vmbus_connection.connect_cpu,
-					 &ctx->work);
+			schedule_work(&ctx->work);
 			break;
 
 		case CHANNELMSG_OFFERCHANNEL:
+			/*
+			 * The host sends the offer message of a given channel
+			 * before sending the rescind message of the same
+			 * channel.  These messages are sent to the guest's
+			 * connect CPU; the guest then starts processing them
+			 * in the tasklet handler on this CPU:
+			 *
+			 * VMBUS_CONNECT_CPU
+			 *
+			 * [vmbus_on_msg_dpc()]
+			 * atomic_inc()  // CHANNELMSG_OFFERCHANNEL
+			 * queue_work()
+			 * ...
+			 * [vmbus_on_msg_dpc()]
+			 * schedule_work()  // CHANNELMSG_RESCIND_CHANNELOFFER
+			 *
+			 * We rely on the memory-ordering properties of the
+			 * queue_work() and schedule_work() primitives, which
+			 * guarantee that the atomic increment will be visible
+			 * to the CPUs which will execute the offer & rescind
+			 * works by the time these works will start execution.
+			 */
 			atomic_inc(&vmbus_connection.offer_in_progress);
-			queue_work_on(vmbus_connection.connect_cpu,
-				      vmbus_connection.work_queue,
-				      &ctx->work);
-			break;
+			fallthrough;
 
 		default:
 			queue_work(vmbus_connection.work_queue, &ctx->work);
···
 	WARN_ON(!is_hvsock_channel(channel));
 
 	/*
-	 * sizeof(*ctx) is small and the allocation should really not fail,
+	 * Allocation size is small and the allocation should really not fail,
 	 * otherwise the state of the hv_sock connections ends up in limbo.
 	 */
-	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL | __GFP_NOFAIL);
+	ctx = kzalloc(sizeof(*ctx) + sizeof(*rescind),
+		      GFP_KERNEL | __GFP_NOFAIL);
 
 	/*
 	 * So far, these are not really used by Linux. Just set them to the
···
 	ctx->msg.header.payload_size = sizeof(*rescind);
 
 	/* These values are actually used by Linux. */
-	rescind = (struct vmbus_channel_rescind_offer *)ctx->msg.u.payload;
+	rescind = (struct vmbus_channel_rescind_offer *)ctx->msg.payload;
 	rescind->header.msgtype = CHANNELMSG_RESCIND_CHANNELOFFER;
 	rescind->child_relid = channel->offermsg.child_relid;
 
 	INIT_WORK(&ctx->work, vmbus_onmessage_work);
 
-	queue_work_on(vmbus_connection.connect_cpu,
-		      vmbus_connection.work_queue,
-		      &ctx->work);
+	queue_work(vmbus_connection.work_queue, &ctx->work);
 }
 #endif /* CONFIG_PM_SLEEP */
-
-/*
- * Direct callback for channels using other deferred processing
- */
-static void vmbus_channel_isr(struct vmbus_channel *channel)
-{
-	void (*callback_fn)(void *);
-
-	callback_fn = READ_ONCE(channel->onchannel_callback);
-	if (likely(callback_fn != NULL))
-		(*callback_fn)(channel->channel_callback_context);
-}
 
 /*
  * Schedule all channels with events pending
···
 		return;
 
 	for_each_set_bit(relid, recv_int_page, maxbits) {
+		void (*callback_fn)(void *context);
 		struct vmbus_channel *channel;
 
 		if (!sync_test_and_clear_bit(relid, recv_int_page))
···
 		if (relid == 0)
 			continue;
 
+		/*
+		 * Pairs with the kfree_rcu() in vmbus_chan_release().
+		 * Guarantees that the channel data structure doesn't
+		 * get freed while the channel pointer below is being
+		 * dereferenced.
+		 */
 		rcu_read_lock();
 
 		/* Find channel based on relid */
-		list_for_each_entry_rcu(channel, &hv_cpu->chan_list, percpu_list) {
-			if (channel->offermsg.child_relid != relid)
-				continue;
+		channel = relid2channel(relid);
+		if (channel == NULL)
+			goto sched_unlock_rcu;
 
-			if (channel->rescind)
-				continue;
+		if (channel->rescind)
+			goto sched_unlock_rcu;
 
-			trace_vmbus_chan_sched(channel);
+		/*
+		 * Make sure that the ring buffer data structure doesn't get
+		 * freed while we dereference the ring buffer pointer.  Test
+		 * for the channel's onchannel_callback being NULL within a
+		 * sched_lock critical section.  See also the inline comments
+		 * in vmbus_reset_channel_cb().
+		 */
+		spin_lock(&channel->sched_lock);
 
-			++channel->interrupts;
+		callback_fn = channel->onchannel_callback;
+		if (unlikely(callback_fn == NULL))
+			goto sched_unlock;
 
-			switch (channel->callback_mode) {
-			case HV_CALL_ISR:
-				vmbus_channel_isr(channel);
-				break;
+		trace_vmbus_chan_sched(channel);
 
-			case HV_CALL_BATCHED:
-				hv_begin_read(&channel->inbound);
-				/* fallthrough */
-			case HV_CALL_DIRECT:
-				tasklet_schedule(&channel->callback_event);
-			}
+		++channel->interrupts;
+
+		switch (channel->callback_mode) {
+		case HV_CALL_ISR:
+			(*callback_fn)(channel->channel_callback_context);
+			break;
+
+		case HV_CALL_BATCHED:
+			hv_begin_read(&channel->inbound);
+			fallthrough;
+		case HV_CALL_DIRECT:
+			tasklet_schedule(&channel->callback_event);
 		}
 
+sched_unlock:
+		spin_unlock(&channel->sched_lock);
+sched_unlock_rcu:
 		rcu_read_unlock();
 	}
 }
···
 {
 	int ret;
 
-	/* Hypervisor initialization...setup hypercall page..etc */
 	ret = hv_init();
 	if (ret != 0) {
 		pr_err("Unable to initialize the hypervisor - 0x%x\n", ret);
···
 	return attribute->show(chan, buf);
 }
 
+static ssize_t vmbus_chan_attr_store(struct kobject *kobj,
+				     struct attribute *attr, const char *buf,
+				     size_t count)
+{
+	const struct vmbus_chan_attribute *attribute
+		= container_of(attr, struct vmbus_chan_attribute, attr);
+	struct vmbus_channel *chan
+		= container_of(kobj, struct vmbus_channel, kobj);
+
+	if (!attribute->store)
+		return -EIO;
+
+	return attribute->store(chan, buf, count);
+}
+
 static const struct sysfs_ops vmbus_chan_sysfs_ops = {
 	.show = vmbus_chan_attr_show,
+	.store = vmbus_chan_attr_store,
 };
 
 static ssize_t out_mask_show(struct vmbus_channel *channel, char *buf)
···
 }
 static VMBUS_CHAN_ATTR_RO(write_avail);
 
-static ssize_t show_target_cpu(struct vmbus_channel *channel, char *buf)
+static ssize_t target_cpu_show(struct vmbus_channel *channel, char *buf)
 {
 	return sprintf(buf, "%u\n", channel->target_cpu);
 }
-static VMBUS_CHAN_ATTR(cpu, S_IRUGO, show_target_cpu, NULL);
+static ssize_t target_cpu_store(struct vmbus_channel *channel,
+				const char *buf, size_t count)
+{
+	u32 target_cpu, origin_cpu;
+	ssize_t ret = count;
+
+	if (vmbus_proto_version < VERSION_WIN10_V4_1)
+		return -EIO;
+
+	if (sscanf(buf, "%uu", &target_cpu) != 1)
+		return -EIO;
+
+	/* Validate target_cpu for the cpumask_test_cpu() operation below. */
+	if (target_cpu >= nr_cpumask_bits)
+		return -EINVAL;
+
+	/* No CPUs should come up or down during this. */
+	cpus_read_lock();
+
+	if (!cpumask_test_cpu(target_cpu, cpu_online_mask)) {
+		cpus_read_unlock();
+		return -EINVAL;
+	}
+
+	/*
+	 * Synchronizes target_cpu_store() and channel closure:
+	 *
+	 * { Initially: state = CHANNEL_OPENED }
+	 *
+	 * CPU1				CPU2
+	 *
+	 * [target_cpu_store()]		[vmbus_disconnect_ring()]
+	 *
+	 * LOCK channel_mutex		LOCK channel_mutex
+	 * LOAD r1 = state		LOAD r2 = state
+	 * IF (r1 == CHANNEL_OPENED)	IF (r2 == CHANNEL_OPENED)
+	 *   SEND MODIFYCHANNEL		  STORE state = CHANNEL_OPEN
+	 *   [...]			  SEND CLOSECHANNEL
+	 * UNLOCK channel_mutex		UNLOCK channel_mutex
+	 *
+	 * Forbids: r1 == r2 == CHANNEL_OPENED (i.e., CPU1's LOCK precedes
+	 * 		CPU2's LOCK) && CPU2's SEND precedes CPU1's SEND
+	 *
+	 * Note.  The host processes the channel messages "sequentially", in
+	 * the order in which they are received on a per-partition basis.
+	 */
+	mutex_lock(&vmbus_connection.channel_mutex);
+
+	/*
+	 * Hyper-V will ignore MODIFYCHANNEL messages for "non-open" channels;
+	 * avoid sending the message and fail here for such channels.
+	 */
+	if (channel->state != CHANNEL_OPENED_STATE) {
+		ret = -EIO;
+		goto cpu_store_unlock;
+	}
+
+	origin_cpu = channel->target_cpu;
+	if (target_cpu == origin_cpu)
+		goto cpu_store_unlock;
+
+	if (vmbus_send_modifychannel(channel->offermsg.child_relid,
+				     hv_cpu_number_to_vp_number(target_cpu))) {
+		ret = -EIO;
+		goto cpu_store_unlock;
+	}
+
+	/*
+	 * Warning.  At this point, there is *no* guarantee that the host will
+	 * have successfully processed the vmbus_send_modifychannel() request.
+	 * See the header comment of vmbus_send_modifychannel() for more info.
+	 *
+	 * Lags in the processing of the above vmbus_send_modifychannel() can
+	 * result in missed interrupts if the "old" target CPU is taken offline
+	 * before Hyper-V starts sending interrupts to the "new" target CPU.
+	 * But apart from this offlining scenario, the code tolerates such
+	 * lags.  It will function correctly even if a channel interrupt comes
+	 * in on a CPU that is different from the channel target_cpu value.
+	 */
+
+	channel->target_cpu = target_cpu;
+	channel->target_vp = hv_cpu_number_to_vp_number(target_cpu);
+	channel->numa_node = cpu_to_node(target_cpu);
+
+	/* See init_vp_index(). */
+	if (hv_is_perf_channel(channel))
+		hv_update_alloced_cpus(origin_cpu, target_cpu);
+
+	/* Currently set only for storvsc channels. */
+	if (channel->change_target_cpu_callback) {
+		(*channel->change_target_cpu_callback)(channel,
+				origin_cpu, target_cpu);
+	}
+
+cpu_store_unlock:
+	mutex_unlock(&vmbus_connection.channel_mutex);
+	cpus_read_unlock();
+	return ret;
+}
+static VMBUS_CHAN_ATTR(cpu, 0644, target_cpu_show, target_cpu_store);
 
 static ssize_t channel_pending_show(struct vmbus_channel *channel,
 				    char *buf)
···
 	int ret;
 
 	dev_set_name(&child_device_obj->device, "%pUl",
-		     child_device_obj->channel->offermsg.offer.if_instance.b);
+		     &child_device_obj->channel->offermsg.offer.if_instance);
 
 	child_device_obj->device.bus = &hv_bus;
 	child_device_obj->device.parent = &hv_acpi_dev->dev;
···
 
 	list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
 		/*
-		 * Invalidate the field. Upon resume, vmbus_onoffer() will fix
-		 * up the field, and the other fields (if necessary).
+		 * Remove the channel from the array of channels and invalidate
+		 * the channel's relid.  Upon resume, vmbus_onoffer() will fix
+		 * up the relid (and other fields, if necessary) and add the
+		 * channel back to the array.
 		 */
+		vmbus_channel_unmap_relid(channel);
 		channel->offermsg.child_relid = INVALID_RELID;
 
 		if (is_hvsock_channel(channel)) {
···
 	hv_debug_rm_all_dir();
 
 	vmbus_free_channels();
+	kfree(vmbus_connection.channels);
 
 	if (ms_hyperv.misc_features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE) {
 		kmsg_dump_unregister(&hv_kmsg_dumper);

drivers/net/hyperv/netvsc.c

···
 
 	RCU_INIT_POINTER(net_device_ctx->nvdev, NULL);
 
-	/* And disassociate NAPI context from device */
-	for (i = 0; i < net_device->num_chn; i++)
+	/* Disable NAPI and disassociate its context from the device. */
+	for (i = 0; i < net_device->num_chn; i++) {
+		/* See also vmbus_reset_channel_cb(). */
+		napi_disable(&net_device->chan_table[i].napi);
 		netif_napi_del(&net_device->chan_table[i].napi);
+	}
 
 	/*
 	 * At this point, no one should be accessing net_device

drivers/pci/controller/pci-hyperv.c

···
 {
 	struct irq_cfg *cfg = irqd_cfg(data);
 	struct hv_pcibus_device *hbus;
+	struct vmbus_channel *channel;
 	struct hv_pci_dev *hpdev;
 	struct pci_bus *pbus;
 	struct pci_dev *pdev;
 	struct cpumask *dest;
-	unsigned long flags;
 	struct compose_comp_ctxt comp;
 	struct tran_int_desc *int_desc;
 	struct {
···
 	dest = irq_data_get_effective_affinity_mask(data);
 	pbus = pdev->bus;
 	hbus = container_of(pbus->sysdata, struct hv_pcibus_device, sysdata);
+	channel = hbus->hdev->channel;
 	hpdev = get_pcichild_wslot(hbus, devfn_to_wslot(pdev->devfn));
 	if (!hpdev)
 		goto return_null_message;
···
 	}
 
 	/*
+	 * Prevents hv_pci_onchannelcallback() from running concurrently
+	 * in the tasklet.
+	 */
+	tasklet_disable(&channel->callback_event);
+
+	/*
 	 * Since this function is called with IRQ locks held, can't
 	 * do normal wait for completion; instead poll.
 	 */
 	while (!try_wait_for_completion(&comp.comp_pkt.host_event)) {
+		unsigned long flags;
+
 		/* 0xFFFF means an invalid PCI VENDOR ID. */
 		if (hv_pcifront_get_vendor_id(hpdev) == 0xFFFF) {
 			dev_err_once(&hbus->hdev->device,
 				     "the device has gone\n");
-			goto free_int_desc;
+			goto enable_tasklet;
 		}
 
 		/*
-		 * When the higher level interrupt code calls us with
-		 * interrupt disabled, we must poll the channel by calling
-		 * the channel callback directly when channel->target_cpu is
-		 * the current CPU. When the higher level interrupt code
-		 * calls us with interrupt enabled, let's add the
-		 * local_irq_save()/restore() to avoid race:
-		 * hv_pci_onchannelcallback() can also run in tasklet.
+		 * Make sure that the ring buffer data structure doesn't get
+		 * freed while we dereference the ring buffer pointer.  Test
+		 * for the channel's onchannel_callback being NULL within a
+		 * sched_lock critical section.  See also the inline comments
+		 * in vmbus_reset_channel_cb().
 		 */
-		local_irq_save(flags);
-
-		if (hbus->hdev->channel->target_cpu == smp_processor_id())
-			hv_pci_onchannelcallback(hbus);
-
-		local_irq_restore(flags);
+		spin_lock_irqsave(&channel->sched_lock, flags);
+		if (unlikely(channel->onchannel_callback == NULL)) {
+			spin_unlock_irqrestore(&channel->sched_lock, flags);
+			goto enable_tasklet;
+		}
+		hv_pci_onchannelcallback(hbus);
+		spin_unlock_irqrestore(&channel->sched_lock, flags);
 
 		if (hpdev->state == hv_pcichild_ejecting) {
 			dev_err_once(&hbus->hdev->device,
 				     "the device is being ejected\n");
-			goto free_int_desc;
+			goto enable_tasklet;
 		}
 
 		udelay(100);
 	}
+
+	tasklet_enable(&channel->callback_event);
 
 	if (comp.comp_pkt.completion_status < 0) {
 		dev_err(&hbus->hdev->device,
···
 	put_pcichild(hpdev);
 	return;
 
+enable_tasklet:
+	tasklet_enable(&channel->callback_event);
 free_int_desc:
 	kfree(int_desc);
 drop_reference:

drivers/scsi/storvsc_drv.c

···
 
 }
 
+static void storvsc_change_target_cpu(struct vmbus_channel *channel, u32 old,
+				      u32 new)
+{
+	struct storvsc_device *stor_device;
+	struct vmbus_channel *cur_chn;
+	bool old_is_alloced = false;
+	struct hv_device *device;
+	unsigned long flags;
+	int cpu;
+
+	device = channel->primary_channel ?
+			channel->primary_channel->device_obj
+				: channel->device_obj;
+	stor_device = get_out_stor_device(device);
+	if (!stor_device)
+		return;
+
+	/* See storvsc_do_io() -> get_og_chn(). */
+	spin_lock_irqsave(&device->channel->lock, flags);
+
+	/*
+	 * Determines if the storvsc device has other channels assigned to
+	 * the "old" CPU to update the alloced_cpus mask and the stor_chns
+	 * array.
+	 */
+	if (device->channel != channel && device->channel->target_cpu == old) {
+		cur_chn = device->channel;
+		old_is_alloced = true;
+		goto old_is_alloced;
+	}
+	list_for_each_entry(cur_chn, &device->channel->sc_list, sc_list) {
+		if (cur_chn == channel)
+			continue;
+		if (cur_chn->target_cpu == old) {
+			old_is_alloced = true;
+			goto old_is_alloced;
+		}
+	}
+
+old_is_alloced:
+	if (old_is_alloced)
+		WRITE_ONCE(stor_device->stor_chns[old], cur_chn);
+	else
+		cpumask_clear_cpu(old, &stor_device->alloced_cpus);
+
+	/* "Flush" the stor_chns array. */
+	for_each_possible_cpu(cpu) {
+		if (stor_device->stor_chns[cpu] && !cpumask_test_cpu(
+					cpu, &stor_device->alloced_cpus))
+			WRITE_ONCE(stor_device->stor_chns[cpu], NULL);
+	}
+
+	WRITE_ONCE(stor_device->stor_chns[new], channel);
+	cpumask_set_cpu(new, &stor_device->alloced_cpus);
+
+	spin_unlock_irqrestore(&device->channel->lock, flags);
+}
+
 static void handle_sc_creation(struct vmbus_channel *new_sc)
 {
 	struct hv_device *device = new_sc->primary_channel->device_obj;
···
 		dev_err(dev, "Failed to open sub-channel: err=%d\n", ret);
 		return;
 	}
+
+	new_sc->change_target_cpu_callback = storvsc_change_target_cpu;
 
 	/* Add the sub-channel to the array of available channels. */
 	stor_device->stor_chns[new_sc->target_cpu] = new_sc;
···
 					 GFP_KERNEL);
 	if (stor_device->stor_chns == NULL)
 		return -ENOMEM;
+
+	device->channel->change_target_cpu_callback = storvsc_change_target_cpu;
 
 	stor_device->stor_chns[device->channel->target_cpu] = device->channel;
 	cpumask_set_cpu(device->channel->target_cpu,
···
 	const struct cpumask *node_mask;
 	int num_channels, tgt_cpu;
 
-	if (stor_device->num_sc == 0)
+	if (stor_device->num_sc == 0) {
+		stor_device->stor_chns[q_num] = stor_device->device->channel;
 		return stor_device->device->channel;
+	}
 
 	/*
 	 * Our channel array is sparsley populated and we
···
 	 * The strategy is simple:
 	 * I. Ensure NUMA locality
 	 * II. Distribute evenly (best effort)
-	 * III. Mapping is persistent.
 	 */
 
 	node_mask = cpumask_of_node(cpu_to_node(q_num));
···
 		if (cpumask_test_cpu(tgt_cpu, node_mask))
 			num_channels++;
 	}
-	if (num_channels == 0)
+	if (num_channels == 0) {
+		stor_device->stor_chns[q_num] = stor_device->device->channel;
 		return stor_device->device->channel;
+	}
 
 	hash_qnum = q_num;
 	while (hash_qnum >= num_channels)
···
 	struct storvsc_device *stor_device;
 	struct vstor_packet *vstor_packet;
 	struct vmbus_channel *outgoing_channel, *channel;
+	unsigned long flags;
 	int ret = 0;
 	const struct cpumask *node_mask;
 	int tgt_cpu;
···
 
 	request->device  = device;
 	/*
-	 * Select an an appropriate channel to send the request out.
+	 * Select an appropriate channel to send the request out.
 	 */
-	if (stor_device->stor_chns[q_num] != NULL) {
-		outgoing_channel = stor_device->stor_chns[q_num];
+	/* See storvsc_change_target_cpu(). */
+	outgoing_channel = READ_ONCE(stor_device->stor_chns[q_num]);
+	if (outgoing_channel != NULL) {
 		if (outgoing_channel->target_cpu == q_num) {
 			/*
 			 * Ideally, we want to pick a different channel if
···
 					continue;
 				if (tgt_cpu == q_num)
 					continue;
-				channel = stor_device->stor_chns[tgt_cpu];
+				channel = READ_ONCE(
+					stor_device->stor_chns[tgt_cpu]);
+				if (channel == NULL)
+					continue;
 				if (hv_get_avail_to_write_percent(
 							&channel->outbound)
 						> ring_avail_percent_lowater) {
···
 			for_each_cpu(tgt_cpu, &stor_device->alloced_cpus) {
 				if (cpumask_test_cpu(tgt_cpu, node_mask))
 					continue;
-				channel = stor_device->stor_chns[tgt_cpu];
+				channel = READ_ONCE(
+					stor_device->stor_chns[tgt_cpu]);
+				if (channel == NULL)
+					continue;
 				if (hv_get_avail_to_write_percent(
 							&channel->outbound)
 						> ring_avail_percent_lowater) {
···
 			}
 		}
 	} else {
+		spin_lock_irqsave(&device->channel->lock, flags);
+		outgoing_channel = stor_device->stor_chns[q_num];
+		if (outgoing_channel != NULL) {
+			spin_unlock_irqrestore(&device->channel->lock, flags);
+			goto found_channel;
+		}
 		outgoing_channel = get_og_chn(stor_device, q_num);
+		spin_unlock_irqrestore(&device->channel->lock, flags);
 	}
 
 found_channel:

include/asm-generic/hyperv-tlfs.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*
+ * This file contains definitions from Hyper-V Hypervisor Top-Level Functional
+ * Specification (TLFS):
+ * https://docs.microsoft.com/en-us/virtualization/hyper-v-on-windows/reference/tlfs
+ */
+
+#ifndef _ASM_GENERIC_HYPERV_TLFS_H
+#define _ASM_GENERIC_HYPERV_TLFS_H
+
+#include <linux/types.h>
+#include <linux/bits.h>
+#include <linux/time64.h>
+
+/*
+ * While not explicitly listed in the TLFS, Hyper-V always runs with a page size
+ * of 4096. These definitions are used when communicating with Hyper-V using
+ * guest physical pages and guest physical page addresses, since the guest page
+ * size may not be 4096 on all architectures.
+ */
+#define HV_HYP_PAGE_SHIFT      12
+#define HV_HYP_PAGE_SIZE       BIT(HV_HYP_PAGE_SHIFT)
+#define HV_HYP_PAGE_MASK       (~(HV_HYP_PAGE_SIZE - 1))
+
+/*
+ * Hyper-V provides two categories of flags relevant to guest VMs.  The
+ * "Features" category indicates specific functionality that is available
+ * to guests on this particular instance of Hyper-V. The "Features"
+ * are presented in four groups, each of which is 32 bits. The group A
+ * and B definitions are common across architectures and are listed here.
+ * However, not all flags are relevant on all architectures.
+ *
+ * Groups C and D vary across architectures and are listed in the
+ * architecture specific portion of hyperv-tlfs.h. Some of these flags exist
+ * on multiple architectures, but the bit positions are different so they
+ * cannot appear in the generic portion of hyperv-tlfs.h.
+ *
+ * The "Enlightenments" category provides recommendations on whether to use
+ * specific enlightenments that are available. The Enlighenments are a single
+ * group of 32 bits, but they vary across architectures and are listed in
+ * the architecture specific portion of hyperv-tlfs.h.
+ */
+
+/*
+ * Group A Features.
+ */
+
+/* VP Runtime register available */
+#define HV_MSR_VP_RUNTIME_AVAILABLE		BIT(0)
+/* Partition Reference Counter available*/
+#define HV_MSR_TIME_REF_COUNT_AVAILABLE		BIT(1)
+/* Basic SynIC register available */
+#define HV_MSR_SYNIC_AVAILABLE			BIT(2)
+/* Synthetic Timer registers available */
+#define HV_MSR_SYNTIMER_AVAILABLE		BIT(3)
+/* Virtual APIC assist and VP assist page registers available */
+#define HV_MSR_APIC_ACCESS_AVAILABLE		BIT(4)
+/* Hypercall and Guest OS ID registers available*/
+#define HV_MSR_HYPERCALL_AVAILABLE		BIT(5)
+/* Access virtual processor index register available*/
+#define HV_MSR_VP_INDEX_AVAILABLE		BIT(6)
+/* Virtual system reset register available*/
+#define HV_MSR_RESET_AVAILABLE			BIT(7)
+/* Access statistics page registers available */
+#define HV_MSR_STAT_PAGES_AVAILABLE		BIT(8)
+/* Partition reference TSC register is available */
+#define HV_MSR_REFERENCE_TSC_AVAILABLE		BIT(9)
+/* Partition Guest IDLE register is available */
+#define HV_MSR_GUEST_IDLE_AVAILABLE		BIT(10)
+/* Partition local APIC and TSC frequency registers available */
+#define HV_ACCESS_FREQUENCY_MSRS		BIT(11)
+/* AccessReenlightenmentControls privilege */
+#define HV_ACCESS_REENLIGHTENMENT		BIT(13)
+/* AccessTscInvariantControls privilege */
+#define HV_ACCESS_TSC_INVARIANT			BIT(15)
+
+/*
+ * Group B features.
+ */
+#define HV_CREATE_PARTITIONS			BIT(0)
+#define HV_ACCESS_PARTITION_ID			BIT(1)
+#define HV_ACCESS_MEMORY_POOL			BIT(2)
+#define HV_ADJUST_MESSAGE_BUFFERS		BIT(3)
+#define HV_POST_MESSAGES			BIT(4)
+#define HV_SIGNAL_EVENTS			BIT(5)
+#define HV_CREATE_PORT				BIT(6)
+#define HV_CONNECT_PORT				BIT(7)
+#define HV_ACCESS_STATS				BIT(8)
+#define HV_DEBUGGING				BIT(11)
+#define HV_CPU_POWER_MANAGEMENT			BIT(12)
+
+
+/*
+ * TSC page layout.
+ */
+struct ms_hyperv_tsc_page {
+	volatile u32 tsc_sequence;
+	u32 reserved1;
+	volatile u64 tsc_scale;
+	volatile s64 tsc_offset;
+} __packed;
+
+/*
+ * The guest OS needs to register the guest ID with the hypervisor.
+ * The guest ID is a 64 bit entity and the structure of this ID is
+ * specified in the Hyper-V specification:
+ *
+ * msdn.microsoft.com/en-us/library/windows/hardware/ff542653%28v=vs.85%29.aspx
+ *
+ * While the current guideline does not specify how Linux guest ID(s)
+ * need to be generated, our plan is to publish the guidelines for
+ * Linux and other guest operating systems that currently are hosted
+ * on Hyper-V. The implementation here conforms to this yet
+ * unpublished guidelines.
+ *
+ *
+ * Bit(s)
+ * 63 - Indicates if the OS is Open Source or not; 1 is Open Source
+ * 62:56 - Os Type; Linux is 0x100
+ * 55:48 - Distro specific identification
+ * 47:16 - Linux kernel version number
+ * 15:0  - Distro specific identification
+ *
+ *
+ */
+
+#define HV_LINUX_VENDOR_ID              0x8100
+
+/*
+ * Crash notification flags.
+ */
+#define HV_CRASH_CTL_CRASH_NOTIFY_MSG		BIT_ULL(62)
+#define HV_CRASH_CTL_CRASH_NOTIFY		BIT_ULL(63)
+
+/* Declare the various hypercall operations. */
+#define HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE	0x0002
+#define HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST	0x0003
+#define HVCALL_NOTIFY_LONG_SPIN_WAIT		0x0008
+#define HVCALL_SEND_IPI				0x000b
+#define HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE_EX	0x0013
+#define HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST_EX	0x0014
+#define HVCALL_SEND_IPI_EX			0x0015
+#define HVCALL_GET_VP_REGISTERS			0x0050
+#define HVCALL_SET_VP_REGISTERS			0x0051
+#define HVCALL_POST_MESSAGE			0x005c
+#define HVCALL_SIGNAL_EVENT			0x005d
+#define HVCALL_RETARGET_INTERRUPT		0x007e
+#define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_SPACE 0x00af
+#define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_LIST 0x00b0
+
+#define HV_FLUSH_ALL_PROCESSORS			BIT(0)
+#define HV_FLUSH_ALL_VIRTUAL_ADDRESS_SPACES	BIT(1)
+#define HV_FLUSH_NON_GLOBAL_MAPPINGS_ONLY	BIT(2)
+#define HV_FLUSH_USE_EXTENDED_RANGE_FORMAT	BIT(3)
+
+enum HV_GENERIC_SET_FORMAT {
+	HV_GENERIC_SET_SPARSE_4K,
+	HV_GENERIC_SET_ALL,
+};
+
+#define HV_PARTITION_ID_SELF		((u64)-1)
+#define HV_VP_INDEX_SELF		((u32)-2)
+
+#define HV_HYPERCALL_RESULT_MASK	GENMASK_ULL(15, 0)
+#define HV_HYPERCALL_FAST_BIT		BIT(16)
+#define HV_HYPERCALL_VARHEAD_OFFSET	17
+#define HV_HYPERCALL_REP_COMP_OFFSET	32
+#define HV_HYPERCALL_REP_COMP_1		BIT_ULL(32)
+#define HV_HYPERCALL_REP_COMP_MASK	GENMASK_ULL(43, 32)
+#define HV_HYPERCALL_REP_START_OFFSET	48
+#define HV_HYPERCALL_REP_START_MASK	GENMASK_ULL(59, 48)
+
+/* hypercall status code */
+#define HV_STATUS_SUCCESS			0
+#define HV_STATUS_INVALID_HYPERCALL_CODE	2
+#define HV_STATUS_INVALID_HYPERCALL_INPUT	3
+#define HV_STATUS_INVALID_ALIGNMENT		4
+#define HV_STATUS_INVALID_PARAMETER		5
+#define HV_STATUS_INSUFFICIENT_MEMORY		11
+#define HV_STATUS_INVALID_PORT_ID		17
+#define HV_STATUS_INVALID_CONNECTION_ID		18
+#define HV_STATUS_INSUFFICIENT_BUFFERS		19
+
+/*
+ * The Hyper-V TimeRefCount register and the TSC
+ * page provide a guest VM clock with 100ns tick rate
+ */
+#define HV_CLOCK_HZ (NSEC_PER_SEC/100)
+
+/* Define the number of synthetic interrupt sources. */
+#define HV_SYNIC_SINT_COUNT		(16)
+/* Define the expected SynIC version. */
+#define HV_SYNIC_VERSION_1		(0x1)
+/* Valid SynIC vectors are 16-255. */
+#define HV_SYNIC_FIRST_VALID_VECTOR	(16)
+
+#define HV_SYNIC_CONTROL_ENABLE		(1ULL << 0)
+#define HV_SYNIC_SIMP_ENABLE		(1ULL << 0)
+#define HV_SYNIC_SIEFP_ENABLE		(1ULL << 0)
+#define HV_SYNIC_SINT_MASKED		(1ULL << 16)
+#define HV_SYNIC_SINT_AUTO_EOI		(1ULL << 17)
+#define HV_SYNIC_SINT_VECTOR_MASK	(0xFF)
+
+#define HV_SYNIC_STIMER_COUNT		(4)
+
+/* Define synthetic interrupt controller message constants. */
+#define HV_MESSAGE_SIZE			(256)
+#define HV_MESSAGE_PAYLOAD_BYTE_COUNT	(240)
+#define HV_MESSAGE_PAYLOAD_QWORD_COUNT	(30)
+
+/* Define synthetic interrupt controller message flags. */
+union hv_message_flags {
+	__u8 asu8;
+	struct {
+		__u8 msg_pending:1;
+		__u8 reserved:7;
+	} __packed;
+};
+
+/* Define port identifier type. */
+union hv_port_id {
+	__u32 asu32;
+	struct {
+		__u32 id:24;
+		__u32 reserved:8;
+	} __packed u;
+};
+
+/* Define synthetic interrupt controller message header. */
+struct hv_message_header {
+	__u32 message_type;
+	__u8 payload_size;
+	union hv_message_flags message_flags;
+	__u8 reserved[2];
+	union {
+		__u64 sender;
+		union hv_port_id port;
+	};
+} __packed;
+
+/* Define synthetic interrupt controller message format. */
+struct hv_message {
+	struct hv_message_header header;
+	union {
+		__u64 payload[HV_MESSAGE_PAYLOAD_QWORD_COUNT];
+	} u;
+} __packed;
+
+/* Define the synthetic interrupt message page layout. */
+struct hv_message_page {
+	struct hv_message sint_message[HV_SYNIC_SINT_COUNT];
+} __packed;
+
+/* Define timer message payload structure. */
+struct hv_timer_message_payload {
+	__u32 timer_index;
+	__u32 reserved;
+	__u64 expiration_time;	/* When the timer expired */
+	__u64 delivery_time;	/* When the message was delivered */
+} __packed;
+
+
+/* Define synthetic interrupt controller flag constants. */
+#define HV_EVENT_FLAGS_COUNT		(256 * 8)
+#define HV_EVENT_FLAGS_LONG_COUNT	(256 / sizeof(unsigned long))
+
+/*
+ * Synthetic timer configuration.
+ */
+union hv_stimer_config {
+	u64 as_uint64;
+	struct {
+		u64 enable:1;
+		u64 periodic:1;
+		u64 lazy:1;
+		u64 auto_enable:1;
+		u64 apic_vector:8;
+		u64 direct_mode:1;
+		u64 reserved_z0:3;
+		u64 sintx:4;
+		u64 reserved_z1:44;
+	} __packed;
+};
+
+
+/* Define the synthetic interrupt controller event flags format. */
+union hv_synic_event_flags {
+	unsigned long flags[HV_EVENT_FLAGS_LONG_COUNT];
+};
+
+/* Define SynIC control register. */
+union hv_synic_scontrol {
+	u64 as_uint64;
+	struct {
+		u64 enable:1;
+		u64 reserved:63;
+	} __packed;
+};
+
+/* Define synthetic interrupt source. */
+union hv_synic_sint {
+	u64 as_uint64;
+	struct {
+		u64 vector:8;
+		u64 reserved1:8;
+		u64 masked:1;
+		u64 auto_eoi:1;
+		u64 polling:1;
+		u64 reserved2:45;
+	} __packed;
+};
+
+/* Define the format of the SIMP register */
+union hv_synic_simp {
+	u64 as_uint64;
+	struct {
+		u64 simp_enabled:1;
+		u64 preserved:11;
+		u64 base_simp_gpa:52;
+	} __packed;
+};
+
+/* Define the format of the SIEFP register */
+union hv_synic_siefp {
+	u64 as_uint64;
+	struct {
+		u64 siefp_enabled:1;
+		u64 preserved:11;
+		u64 base_siefp_gpa:52;
+	} __packed;
+};
+
+struct hv_vpset {
+	u64 format;
+	u64 valid_bank_mask;
+	u64 bank_contents[];
+} __packed;
+
+/* HvCallSendSyntheticClusterIpi hypercall */
+struct hv_send_ipi {
+	u32 vector;
+	u32 reserved;
+	u64 cpu_mask;
+} __packed;
+
+/* HvCallSendSyntheticClusterIpiEx hypercall */
+struct hv_send_ipi_ex {
+	u32 vector;
+	u32 reserved;
+	struct hv_vpset vp_set;
+} __packed;
+
+/* HvFlushGuestPhysicalAddressSpace hypercalls */
+struct hv_guest_mapping_flush {
+	u64 address_space;
+	u64 flags;
+} __packed;
+
+/*
+ *  HV_MAX_FLUSH_PAGES = "additional_pages" + 1. It's limited
+ *  by the bitwidth of "additional_pages" in union hv_gpa_page_range.
+ */
+#define HV_MAX_FLUSH_PAGES (2048)
+
+/* HvFlushGuestPhysicalAddressList hypercall */
+union hv_gpa_page_range {
+	u64 address_space;
+	struct {
+		u64 additional_pages:11;
+		u64 largepage:1;
+		u64 basepfn:52;
+	} page;
+};
+
+/*
+ * All input flush parameters should be in single page. The max flush
+ * count is equal with how many entries of union hv_gpa_page_range can
+ * be populated into the input parameter page.
+ */
+#define HV_MAX_FLUSH_REP_COUNT ((HV_HYP_PAGE_SIZE - 2 * sizeof(u64)) /	\
+				sizeof(union hv_gpa_page_range))
+
+struct hv_guest_mapping_flush_list {
+	u64 address_space;
+	u64 flags;
+	union hv_gpa_page_range gpa_list[HV_MAX_FLUSH_REP_COUNT];
+};
+
+/* HvFlushVirtualAddressSpace, HvFlushVirtualAddressList hypercalls */
+struct hv_tlb_flush {
+	u64 address_space;
+	u64 flags;
+	u64 processor_mask;
+	u64 gva_list[];
+} __packed;
+
+/* HvFlushVirtualAddressSpaceEx, HvFlushVirtualAddressListEx hypercalls */
+struct hv_tlb_flush_ex {
+	u64 address_space;
+	u64 flags;
+	struct hv_vpset hv_vp_set;
+	u64 gva_list[];
+} __packed;
+
+/* HvRetargetDeviceInterrupt hypercall */
+union hv_msi_entry {
+	u64 as_uint64;
+	struct {
+		u32 address;
+		u32 data;
+	} __packed;
+};
+
+struct hv_interrupt_entry {
+	u32 source;			/* 1 for MSI(-X) */
+	u32 reserved1;
+	union hv_msi_entry msi_entry;
+} __packed;
+
+/*
+ * flags for hv_device_interrupt_target.flags
+ */
+#define HV_DEVICE_INTERRUPT_TARGET_MULTICAST		1
+#define HV_DEVICE_INTERRUPT_TARGET_PROCESSOR_SET	2
+
+struct hv_device_interrupt_target {
+	u32 vector;
+	u32 flags;
+	union {
+		u64 vp_mask;
+		struct hv_vpset vp_set;
+	};
+} __packed;
+
+struct hv_retarget_device_interrupt {
+	u64 partition_id;		/* use "self" */
+	u64 device_id;
+	struct hv_interrupt_entry int_entry;
+	u64 reserved2;
+	struct hv_device_interrupt_target int_target;
+} __packed __aligned(8);
+
+
+/* HvGetVpRegisters hypercall input with variable size reg name list*/
+struct hv_get_vp_registers_input {
+	struct {
+		u64 partitionid;
+		u32 vpindex;
+		u8  inputvtl;
+		u8  padding[3];
+	} header;
+	struct input {
+		u32 name0;
+		u32 name1;
+	} element[];
+} __packed;
+
+
+/* HvGetVpRegisters returns an array of these output elements */
+struct hv_get_vp_registers_output {
+	union {
+		struct {
+			u32 a;
+			u32 b;
+			u32 c;
+			u32 d;
+		} as32 __packed;
+		struct {
+			u64 low;
+			u64 high;
+		} as64 __packed;
+	};
+};
+
+/* HvSetVpRegisters hypercall with variable size reg name/value list*/
+struct hv_set_vp_registers_input {
+	struct {
+		u64 partitionid;
+		u32 vpindex;
+		u8  inputvtl;
+		u8  padding[3];
+	} header;
+	struct {
+		u32 name;
+		u32 padding1;
+		u64 padding2;
+		u64 valuelow;
+		u64 valuehigh;
+	} element[];
+} __packed;
+
+#endif

include/linux/hyperv.h

···
 	 * Ring data starts here + RingDataStartOffset
 	 * !!! DO NOT place any fields below this !!!
 	 */
-	u8 buffer[0];
+	u8 buffer[];
 } __packed;
 
 struct hv_ring_buffer_info {
···
 struct gpa_range {
 	u32 byte_count;
 	u32 byte_offset;
-	u64 pfn_array[0];
+	u64 pfn_array[];
 };
 
 /*
···
 	CHANNELMSG_19				= 19,
 	CHANNELMSG_20				= 20,
 	CHANNELMSG_TL_CONNECT_REQUEST		= 21,
-	CHANNELMSG_22				= 22,
+	CHANNELMSG_MODIFYCHANNEL		= 22,
 	CHANNELMSG_TL_CONNECT_RESULT		= 23,
 	CHANNELMSG_COUNT
 };
···
 	u32 gpadl;
 	u16 range_buflen;
 	u16 rangecount;
-	struct gpa_range range[0];
+	struct gpa_range range[];
 } __packed;
 
 /* This is the followup packet that contains more PFNs. */
···
 	struct vmbus_channel_message_header header;
 	u32 msgnumber;
 	u32 gpadl;
-	u64 pfn[0];
+	u64 pfn[];
 } __packed;
 
 struct vmbus_channel_gpadl_created {
···
 	struct vmbus_channel_message_header header;
 	guid_t guest_endpoint_id;
 	guid_t host_service_id;
+} __packed;
+
+/* Modify Channel parameters, cf. vmbus_send_modifychannel() */
+struct vmbus_channel_modifychannel {
+	struct vmbus_channel_message_header header;
+	u32 child_relid;
+	u32 target_vp;
 } __packed;
 
 struct vmbus_channel_version_response {
···
 	 * The channel message that goes out on the "wire".
 	 * It will contain at minimum the VMBUS_CHANNEL_MESSAGE_HEADER header
 	 */
-	unsigned char msg[0];
+	unsigned char msg[];
 };
 
 struct vmbus_close_msg {
···
 		u32 id:24;
 		u32 reserved:8;
 	} u;
-};
-
-enum hv_numa_policy {
-	HV_BALANCED = 0,
-	HV_LOCALIZED,
 };
 
 enum vmbus_device_type {
···
 	void (*onchannel_callback)(void *context);
 	void *channel_callback_context;
 
+	void (*change_target_cpu_callback)(struct vmbus_channel *channel,
+			u32 old, u32 new);
+
+	/*
+	 * Synchronize channel scheduling and channel removal; see the inline
+	 * comments in vmbus_chan_sched() and vmbus_reset_channel_cb().
+	 */
+	spinlock_t sched_lock;
+
 	/*
 	 * A channel can be marked for one of three modes of reading:
 	 *   BATCHED - callback called from taslket and should read
···
 	u32 target_vp;
 	/* The corresponding CPUID in the guest */
 	u32 target_cpu;
-	/*
-	 * State to manage the CPU affiliation of channels.
-	 */
-	struct cpumask alloced_cpus_in_node;
 	int numa_node;
 	/*
 	 * Support for sub-channels. For high performance devices,
···
 	 * Support per-channel state for use by vmbus drivers.
 	 */
 	void *per_channel_state;
-	/*
-	 * To support per-cpu lookup mapping of relid to channel,
-	 * link up channels based on their CPU affinity.
-	 */
-	struct list_head percpu_list;
 
 	/*
 	 * Defer freeing channel until after all cpu's have
···
 	 */
 	bool low_latency;
 
-	/*
-	 * NUMA distribution policy:
-	 * We support two policies:
-	 * 1) Balanced: Here all performance critical channels are
-	 *    distributed evenly amongst all the NUMA nodes.
-	 *    This policy will be the default policy.
-	 * 2) Localized: All channels of a given instance of a
-	 *    performance critical service will be assigned CPUs
-	 *    within a selected NUMA node.
-	 */
-	enum hv_numa_policy affinity_policy;
-
 	bool probe_done;
+
+	/*
+	 * Cache the device ID here for easy access; this is useful, in
+	 * particular, in situations where the channel's device_obj has
+	 * not been allocated/initialized yet.
+	 */
+	u16 device_id;
 
 	/*
 	 * We must offload the handling of the primary/sub channels
···
 	return c->offermsg.offer.sub_channel_index != 0;
 }
 
-static inline void set_channel_affinity_state(struct vmbus_channel *c,
-					      enum hv_numa_policy policy)
-{
-	c->affinity_policy = policy;
-}
-
 static inline void set_channel_read_mode(struct vmbus_channel *c,
 					enum hv_callback_mode mode)
 {
···
 	c->low_latency = false;
 }
 
-void vmbus_onmessage(void *context);
+void vmbus_onmessage(struct vmbus_channel_message_header *hdr);
 
 int vmbus_request_offers(void);
 
···
 
 int vmbus_send_tl_connect_request(const guid_t *shv_guest_servie_id,
 				  const guid_t *shv_host_servie_id);
+int vmbus_send_modifychannel(u32 child_relid, u32 target_vp);
 void vmbus_set_event(struct vmbus_channel *channel);
 
 /* Get the start of the ring buffer. */

include/linux/mod_devicetable.h

···
  * For Hyper-V devices we use the device guid as the id.
  */
 struct hv_vmbus_device_id {
-	uuid_le guid;
+	guid_t guid;
 	kernel_ulong_t driver_data;	/* Data private to the driver */
 };