kvm: Allow build-time configuration of KVM device assignment

We hope to at some point deprecate KVM legacy device assignment in
favor of VFIO-based assignment. Towards that end, allow legacy
device assignment to be deconfigured.

Signed-off-by: Alex Williamson <[e-mail]>
Reviewed-by: Alexander Graf <[e-mail]>
Acked-by: Michael S. Tsirkin <[e-mail]>
Signed-off-by: Gleb Natapov <[e-mail]>

arch/ia64/include/uapi/asm/kvm.h

···
 /* Select x86 specific features in <linux/kvm.h> */
 #define __KVM_HAVE_IOAPIC
 #define __KVM_HAVE_IRQ_LINE
-#define __KVM_HAVE_DEVICE_ASSIGNMENT
 
 /* Architectural interrupt line count. */
 #define KVM_NR_INTERRUPTS 256

arch/ia64/kvm/Kconfig

···
 	tristate "Kernel-based Virtual Machine (KVM) support"
 	depends on BROKEN
 	depends on HAVE_KVM && MODULES
-	# for device assignment:
-	depends on PCI
 	depends on BROKEN
 	select PREEMPT_NOTIFIERS
 	select ANON_INODES
···
 	---help---
 	  Provides support for KVM on Itanium 2 processors equipped with the VT
 	  extensions.
+
+config KVM_DEVICE_ASSIGNMENT
+	bool "KVM legacy PCI device assignment support"
+	depends on KVM && PCI && IOMMU_API
+	default y
+	---help---
+	  Provide support for legacy PCI device assignment through KVM.  The
+	  kernel now also supports a full featured userspace device driver
+	  framework through VFIO, which supersedes much of this support.
+
+	  If unsure, say Y.
 
 source drivers/vhost/Kconfig
 

arch/ia64/kvm/Makefile

···
 asflags-y := -Ivirt/kvm -Iarch/ia64/kvm/
 
 common-objs = $(addprefix ../../../virt/kvm/, kvm_main.o ioapic.o \
-		coalesced_mmio.o irq_comm.o assigned-dev.o irqchip.o)
+		coalesced_mmio.o irq_comm.o)
 
-ifeq ($(CONFIG_IOMMU_API),y)
-common-objs += $(addprefix ../../../virt/kvm/, iommu.o)
+ifeq ($(CONFIG_KVM_DEVICE_ASSIGNMENT),y)
+common-objs += $(addprefix ../../../virt/kvm/, assigned-dev.o iommu.o)
 endif
 
 kvm-objs := $(common-objs) kvm-ia64.o kvm_fw.o

arch/ia64/kvm/kvm-ia64.c

···
 void kvm_arch_destroy_vm(struct kvm *kvm)
 {
 	kvm_iommu_unmap_guest(kvm);
-#ifdef  KVM_CAP_DEVICE_ASSIGNMENT
 	kvm_free_all_assigned_devices(kvm);
-#endif
 	kfree(kvm->arch.vioapic);
 	kvm_release_vm_pages(kvm);
 }

arch/x86/include/uapi/asm/kvm.h

···
 #define __KVM_HAVE_PIT
 #define __KVM_HAVE_IOAPIC
 #define __KVM_HAVE_IRQ_LINE
-#define __KVM_HAVE_DEVICE_ASSIGNMENT
 #define __KVM_HAVE_MSI
 #define __KVM_HAVE_USER_NMI
 #define __KVM_HAVE_GUEST_DEBUG

arch/x86/kvm/Kconfig

···
 	tristate "Kernel-based Virtual Machine (KVM) support"
 	depends on HAVE_KVM
 	depends on HIGH_RES_TIMERS
-	# for device assignment:
-	depends on PCI
 	# for TASKSTATS/TASK_DELAY_ACCT:
 	depends on NET
 	select PREEMPT_NOTIFIERS
···
 	---help---
 	 This option adds a R/W kVM module parameter 'mmu_audit', which allows
 	 audit  KVM MMU at runtime.
+
+config KVM_DEVICE_ASSIGNMENT
+	bool "KVM legacy PCI device assignment support"
+	depends on KVM && PCI && IOMMU_API
+	default y
+	---help---
+	  Provide support for legacy PCI device assignment through KVM.  The
+	  kernel now also supports a full featured userspace device driver
+	  framework through VFIO, which supersedes much of this support.
+
+	  If unsure, say Y.
 
 # OK, it's a little counter-intuitive to do this, but it puts it neatly under
 # the virtualization menu.

arch/x86/kvm/Makefile

···
 
 kvm-y			+= $(addprefix ../../../virt/kvm/, kvm_main.o ioapic.o \
 				coalesced_mmio.o irq_comm.o eventfd.o \
-				assigned-dev.o irqchip.o)
-kvm-$(CONFIG_IOMMU_API)	+= $(addprefix ../../../virt/kvm/, iommu.o)
+				irqchip.o)
+kvm-$(CONFIG_KVM_DEVICE_ASSIGNMENT)	+= $(addprefix ../../../virt/kvm/, \
+				assigned-dev.o iommu.o)
 kvm-$(CONFIG_KVM_ASYNC_PF)	+= $(addprefix ../../../virt/kvm/, async_pf.o)
 
 kvm-y			+= x86.o mmu.o emulate.o i8259.o irq.o lapic.o \

arch/x86/kvm/x86.c

···
 	case KVM_CAP_USER_NMI:
 	case KVM_CAP_REINJECT_CONTROL:
 	case KVM_CAP_IRQ_INJECT_STATUS:
-	case KVM_CAP_ASSIGN_DEV_IRQ:
 	case KVM_CAP_IRQFD:
 	case KVM_CAP_IOEVENTFD:
 	case KVM_CAP_PIT2:
···
 	case KVM_CAP_XSAVE:
 	case KVM_CAP_ASYNC_PF:
 	case KVM_CAP_GET_TSC_KHZ:
-	case KVM_CAP_PCI_2_3:
 	case KVM_CAP_KVMCLOCK_CTRL:
 	case KVM_CAP_READONLY_MEM:
+#ifdef CONFIG_KVM_DEVICE_ASSIGNMENT
+	case KVM_CAP_ASSIGN_DEV_IRQ:
+	case KVM_CAP_PCI_2_3:
+#endif
 		r = 1;
 		break;
 	case KVM_CAP_COALESCED_MMIO:

include/linux/kvm_host.h

···
 
 int kvm_arch_init_vm(struct kvm *kvm, unsigned long type);
 void kvm_arch_destroy_vm(struct kvm *kvm);
-void kvm_free_all_assigned_devices(struct kvm *kvm);
 void kvm_arch_sync_events(struct kvm *kvm);
 
 int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu);
···
 /* For vcpu->arch.iommu_flags */
 #define KVM_IOMMU_CACHE_COHERENCY	0x1
 
-#ifdef CONFIG_IOMMU_API
+#ifdef CONFIG_KVM_DEVICE_ASSIGNMENT
 int kvm_iommu_map_pages(struct kvm *kvm, struct kvm_memory_slot *slot);
 void kvm_iommu_unmap_pages(struct kvm *kvm, struct kvm_memory_slot *slot);
 int kvm_iommu_map_guest(struct kvm *kvm);
···
 		      struct kvm_assigned_dev_kernel *assigned_dev);
 int kvm_deassign_device(struct kvm *kvm,
 			struct kvm_assigned_dev_kernel *assigned_dev);
-#else /* CONFIG_IOMMU_API */
+#else
 static inline int kvm_iommu_map_pages(struct kvm *kvm,
 				      struct kvm_memory_slot *slot)
 {
···
 {
 }
 
-static inline int kvm_iommu_map_guest(struct kvm *kvm)
-{
-	return -ENODEV;
-}
-
 static inline int kvm_iommu_unmap_guest(struct kvm *kvm)
 {
 	return 0;
 }
-
-static inline int kvm_assign_device(struct kvm *kvm,
-		struct kvm_assigned_dev_kernel *assigned_dev)
-{
-	return 0;
-}
-
-static inline int kvm_deassign_device(struct kvm *kvm,
-		struct kvm_assigned_dev_kernel *assigned_dev)
-{
-	return 0;
-}
-#endif /* CONFIG_IOMMU_API */
+#endif
 
 static inline void __guest_enter(void)
 {
···
 
 #endif
 
-#ifdef __KVM_HAVE_DEVICE_ASSIGNMENT
+#ifdef CONFIG_KVM_DEVICE_ASSIGNMENT
 
 long kvm_vm_ioctl_assigned_device(struct kvm *kvm, unsigned ioctl,
 				  unsigned long arg);
+
+void kvm_free_all_assigned_devices(struct kvm *kvm);
 
 #else
 
···
 {
 	return -ENOTTY;
 }
+
+static inline void kvm_free_all_assigned_devices(struct kvm *kvm) {}
 
 #endif
 

include/uapi/linux/kvm.h

···
 #define KVM_CAP_MP_STATE 14
 #define KVM_CAP_COALESCED_MMIO 15
 #define KVM_CAP_SYNC_MMU 16  /* Changes to host mmap are reflected in guest */
-#ifdef __KVM_HAVE_DEVICE_ASSIGNMENT
 #define KVM_CAP_DEVICE_ASSIGNMENT 17
-#endif
 #define KVM_CAP_IOMMU 18
 #ifdef __KVM_HAVE_MSI
 #define KVM_CAP_DEVICE_MSI 20
···
 #endif
 #define KVM_CAP_IRQ_ROUTING 25
 #define KVM_CAP_IRQ_INJECT_STATUS 26
-#ifdef __KVM_HAVE_DEVICE_ASSIGNMENT
 #define KVM_CAP_DEVICE_DEASSIGNMENT 27
-#endif
 #ifdef __KVM_HAVE_MSIX
 #define KVM_CAP_DEVICE_MSIX 28
 #endif