Merge tag 'kvm-ppc-cve-4.15-2' of git://git.kernel.org/pub/scm/linux/kernel/git/paulus/powerpc

Add PPC KVM ioctl to report vulnerability and workaround status to userspace.

Documentation/virtual/kvm/api.txt

···
 or if no page table is present for the addresses (e.g. when using
 hugepages).
 
+4.108 KVM_PPC_GET_CPU_CHAR
+
+Capability: KVM_CAP_PPC_GET_CPU_CHAR
+Architectures: powerpc
+Type: vm ioctl
+Parameters: struct kvm_ppc_cpu_char (out)
+Returns: 0 on successful completion
+	 -EFAULT if struct kvm_ppc_cpu_char cannot be written
+
+This ioctl gives userspace information about certain characteristics
+of the CPU relating to speculative execution of instructions and
+possible information leakage resulting from speculative execution (see
+CVE-2017-5715, CVE-2017-5753 and CVE-2017-5754).  The information is
+returned in struct kvm_ppc_cpu_char, which looks like this:
+
+struct kvm_ppc_cpu_char {
+	__u64	character;		/* characteristics of the CPU */
+	__u64	behaviour;		/* recommended software behaviour */
+	__u64	character_mask;		/* valid bits in character */
+	__u64	behaviour_mask;		/* valid bits in behaviour */
+};
+
+For extensibility, the character_mask and behaviour_mask fields
+indicate which bits of character and behaviour have been filled in by
+the kernel.  If the set of defined bits is extended in future then
+userspace will be able to tell whether it is running on a kernel that
+knows about the new bits.
+
+The character field describes attributes of the CPU which can help
+with preventing inadvertent information disclosure - specifically,
+whether there is an instruction to flash-invalidate the L1 data cache
+(ori 30,30,0 or mtspr SPRN_TRIG2,rN), whether the L1 data cache is set
+to a mode where entries can only be used by the thread that created
+them, whether the bcctr[l] instruction prevents speculation, and
+whether a speculation barrier instruction (ori 31,31,0) is provided.
+
+The behaviour field describes actions that software should take to
+prevent inadvertent information disclosure, and thus describes which
+vulnerabilities the hardware is subject to; specifically whether the
+L1 data cache should be flushed when returning to user mode from the
+kernel, and whether a speculation barrier should be placed between an
+array bounds check and the array access.
+
+These fields use the same bit definitions as the new
+H_GET_CPU_CHARACTERISTICS hypercall.
+
 5. The kvm_run structure
 ------------------------
 

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

···
 	__u32	ap_encodings[8];
 };
 
+/* For KVM_PPC_GET_CPU_CHAR */
+struct kvm_ppc_cpu_char {
+	__u64	character;		/* characteristics of the CPU */
+	__u64	behaviour;		/* recommended software behaviour */
+	__u64	character_mask;		/* valid bits in character */
+	__u64	behaviour_mask;		/* valid bits in behaviour */
+};
+
+/*
+ * Values for character and character_mask.
+ * These are identical to the values used by H_GET_CPU_CHARACTERISTICS.
+ */
+#define KVM_PPC_CPU_CHAR_SPEC_BAR_ORI31		(1ULL << 63)
+#define KVM_PPC_CPU_CHAR_BCCTRL_SERIALISED	(1ULL << 62)
+#define KVM_PPC_CPU_CHAR_L1D_FLUSH_ORI30	(1ULL << 61)
+#define KVM_PPC_CPU_CHAR_L1D_FLUSH_TRIG2	(1ULL << 60)
+#define KVM_PPC_CPU_CHAR_L1D_THREAD_PRIV	(1ULL << 59)
+#define KVM_PPC_CPU_CHAR_BR_HINT_HONOURED	(1ULL << 58)
+#define KVM_PPC_CPU_CHAR_MTTRIG_THR_RECONF	(1ULL << 57)
+#define KVM_PPC_CPU_CHAR_COUNT_CACHE_DIS	(1ULL << 56)
+
+#define KVM_PPC_CPU_BEHAV_FAVOUR_SECURITY	(1ULL << 63)
+#define KVM_PPC_CPU_BEHAV_L1D_FLUSH_PR		(1ULL << 62)
+#define KVM_PPC_CPU_BEHAV_BNDS_CHK_SPEC_BAR	(1ULL << 61)
+
 /* Per-vcpu XICS interrupt controller state */
 #define KVM_REG_PPC_ICP_STATE	(KVM_REG_PPC | KVM_REG_SIZE_U64 | 0x8c)
 

arch/powerpc/kvm/powerpc.c

···
 #include <asm/iommu.h>
 #include <asm/switch_to.h>
 #include <asm/xive.h>
+#ifdef CONFIG_PPC_PSERIES
+#include <asm/hvcall.h>
+#include <asm/plpar_wrappers.h>
+#endif
 
 #include "timing.h"
 #include "irq.h"
···
 #ifdef CONFIG_KVM_XICS
 	case KVM_CAP_IRQ_XICS:
 #endif
+	case KVM_CAP_PPC_GET_CPU_CHAR:
 		r = 1;
 		break;
 
···
 	return r;
 }
 
+#ifdef CONFIG_PPC_BOOK3S_64
+/*
+ * These functions check whether the underlying hardware is safe
+ * against attacks based on observing the effects of speculatively
+ * executed instructions, and whether it supplies instructions for
+ * use in workarounds.  The information comes from firmware, either
+ * via the device tree on powernv platforms or from an hcall on
+ * pseries platforms.
+ */
+#ifdef CONFIG_PPC_PSERIES
+static int pseries_get_cpu_char(struct kvm_ppc_cpu_char *cp)
+{
+	struct h_cpu_char_result c;
+	unsigned long rc;
+
+	if (!machine_is(pseries))
+		return -ENOTTY;
+
+	rc = plpar_get_cpu_characteristics(&c);
+	if (rc == H_SUCCESS) {
+		cp->character = c.character;
+		cp->behaviour = c.behaviour;
+		cp->character_mask = KVM_PPC_CPU_CHAR_SPEC_BAR_ORI31 |
+			KVM_PPC_CPU_CHAR_BCCTRL_SERIALISED |
+			KVM_PPC_CPU_CHAR_L1D_FLUSH_ORI30 |
+			KVM_PPC_CPU_CHAR_L1D_FLUSH_TRIG2 |
+			KVM_PPC_CPU_CHAR_L1D_THREAD_PRIV |
+			KVM_PPC_CPU_CHAR_BR_HINT_HONOURED |
+			KVM_PPC_CPU_CHAR_MTTRIG_THR_RECONF |
+			KVM_PPC_CPU_CHAR_COUNT_CACHE_DIS;
+		cp->behaviour_mask = KVM_PPC_CPU_BEHAV_FAVOUR_SECURITY |
+			KVM_PPC_CPU_BEHAV_L1D_FLUSH_PR |
+			KVM_PPC_CPU_BEHAV_BNDS_CHK_SPEC_BAR;
+	}
+	return 0;
+}
+#else
+static int pseries_get_cpu_char(struct kvm_ppc_cpu_char *cp)
+{
+	return -ENOTTY;
+}
+#endif
+
+static inline bool have_fw_feat(struct device_node *fw_features,
+				const char *state, const char *name)
+{
+	struct device_node *np;
+	bool r = false;
+
+	np = of_get_child_by_name(fw_features, name);
+	if (np) {
+		r = of_property_read_bool(np, state);
+		of_node_put(np);
+	}
+	return r;
+}
+
+static int kvmppc_get_cpu_char(struct kvm_ppc_cpu_char *cp)
+{
+	struct device_node *np, *fw_features;
+	int r;
+
+	memset(cp, 0, sizeof(*cp));
+	r = pseries_get_cpu_char(cp);
+	if (r != -ENOTTY)
+		return r;
+
+	np = of_find_node_by_name(NULL, "ibm,opal");
+	if (np) {
+		fw_features = of_get_child_by_name(np, "fw-features");
+		of_node_put(np);
+		if (!fw_features)
+			return 0;
+		if (have_fw_feat(fw_features, "enabled",
+				 "inst-spec-barrier-ori31,31,0"))
+			cp->character |= KVM_PPC_CPU_CHAR_SPEC_BAR_ORI31;
+		if (have_fw_feat(fw_features, "enabled",
+				 "fw-bcctrl-serialized"))
+			cp->character |= KVM_PPC_CPU_CHAR_BCCTRL_SERIALISED;
+		if (have_fw_feat(fw_features, "enabled",
+				 "inst-l1d-flush-ori30,30,0"))
+			cp->character |= KVM_PPC_CPU_CHAR_L1D_FLUSH_ORI30;
+		if (have_fw_feat(fw_features, "enabled",
+				 "inst-l1d-flush-trig2"))
+			cp->character |= KVM_PPC_CPU_CHAR_L1D_FLUSH_TRIG2;
+		if (have_fw_feat(fw_features, "enabled",
+				 "fw-l1d-thread-split"))
+			cp->character |= KVM_PPC_CPU_CHAR_L1D_THREAD_PRIV;
+		if (have_fw_feat(fw_features, "enabled",
+				 "fw-count-cache-disabled"))
+			cp->character |= KVM_PPC_CPU_CHAR_COUNT_CACHE_DIS;
+		cp->character_mask = KVM_PPC_CPU_CHAR_SPEC_BAR_ORI31 |
+			KVM_PPC_CPU_CHAR_BCCTRL_SERIALISED |
+			KVM_PPC_CPU_CHAR_L1D_FLUSH_ORI30 |
+			KVM_PPC_CPU_CHAR_L1D_FLUSH_TRIG2 |
+			KVM_PPC_CPU_CHAR_L1D_THREAD_PRIV |
+			KVM_PPC_CPU_CHAR_COUNT_CACHE_DIS;
+
+		if (have_fw_feat(fw_features, "enabled",
+				 "speculation-policy-favor-security"))
+			cp->behaviour |= KVM_PPC_CPU_BEHAV_FAVOUR_SECURITY;
+		if (!have_fw_feat(fw_features, "disabled",
+				  "needs-l1d-flush-msr-pr-0-to-1"))
+			cp->behaviour |= KVM_PPC_CPU_BEHAV_L1D_FLUSH_PR;
+		if (!have_fw_feat(fw_features, "disabled",
+				  "needs-spec-barrier-for-bound-checks"))
+			cp->behaviour |= KVM_PPC_CPU_BEHAV_BNDS_CHK_SPEC_BAR;
+		cp->behaviour_mask = KVM_PPC_CPU_BEHAV_FAVOUR_SECURITY |
+			KVM_PPC_CPU_BEHAV_L1D_FLUSH_PR |
+			KVM_PPC_CPU_BEHAV_BNDS_CHK_SPEC_BAR;
+
+		of_node_put(fw_features);
+	}
+
+	return 0;
+}
+#endif
+
 long kvm_arch_vm_ioctl(struct file *filp,
                        unsigned int ioctl, unsigned long arg)
 {
···
 			goto out;
 		r = kvm->arch.kvm_ops->get_rmmu_info(kvm, &info);
 		if (r >= 0 && copy_to_user(argp, &info, sizeof(info)))
+			r = -EFAULT;
+		break;
+	}
+	case KVM_PPC_GET_CPU_CHAR: {
+		struct kvm_ppc_cpu_char cpuchar;
+
+		r = kvmppc_get_cpu_char(&cpuchar);
+		if (r >= 0 && copy_to_user(argp, &cpuchar, sizeof(cpuchar)))
 			r = -EFAULT;
 		break;
 	}

include/uapi/linux/kvm.h

···
 #define KVM_CAP_HYPERV_SYNIC2 148
 #define KVM_CAP_HYPERV_VP_INDEX 149
 #define KVM_CAP_S390_AIS_MIGRATION 150
+#define KVM_CAP_PPC_GET_CPU_CHAR 151
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
···
 #define KVM_PPC_CONFIGURE_V3_MMU  _IOW(KVMIO,  0xaf, struct kvm_ppc_mmuv3_cfg)
 /* Available with KVM_CAP_PPC_RADIX_MMU */
 #define KVM_PPC_GET_RMMU_INFO	  _IOW(KVMIO,  0xb0, struct kvm_ppc_rmmu_info)
+/* Available with KVM_CAP_PPC_GET_CPU_CHAR */
+#define KVM_PPC_GET_CPU_CHAR	  _IOR(KVMIO,  0xb1, struct kvm_ppc_cpu_char)
 
 /* ioctl for vm fd */
 #define KVM_CREATE_DEVICE	  _IOWR(KVMIO,  0xe0, struct kvm_create_device)