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-rw-r--r--Documentation/virt/kvm/api.rst20
-rw-r--r--arch/x86/include/asm/kvm_host.h6
-rw-r--r--arch/x86/kvm/x86.c40
-rw-r--r--include/uapi/linux/kvm.h23
4 files changed, 85 insertions, 4 deletions
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 5d8db4922df6..3b6e3b1628b4 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -6546,6 +6546,7 @@ KVM_RUN_BUS_LOCK flag is used to distinguish between them.
This capability can be used to check / enable 2nd DAWR feature provided
by POWER10 processor.
+
7.24 KVM_CAP_VM_COPY_ENC_CONTEXT_FROM
-------------------------------------
@@ -6603,6 +6604,25 @@ present in the "ibm,hypertas-functions" device-tree property.
This capability is enabled for hypervisors on platforms like POWER9
that support radix MMU.
+7.27 KVM_CAP_EXIT_ON_EMULATION_FAILURE
+--------------------------------------
+
+:Architectures: x86
+:Parameters: args[0] whether the feature should be enabled or not
+
+When this capability is enabled, an emulation failure will result in an exit
+to userspace with KVM_INTERNAL_ERROR (except when the emulator was invoked
+to handle a VMware backdoor instruction). Furthermore, KVM will now provide up
+to 15 instruction bytes for any exit to userspace resulting from an emulation
+failure. When these exits to userspace occur use the emulation_failure struct
+instead of the internal struct. They both have the same layout, but the
+emulation_failure struct matches the content better. It also explicitly
+defines the 'flags' field which is used to describe the fields in the struct
+that are valid (ie: if KVM_INTERNAL_ERROR_EMULATION_FLAG_INSTRUCTION_BYTES is
+set in the 'flags' field then both 'insn_size' and 'insn_bytes' have valid data
+in them.)
+
+
8. Other capabilities.
======================
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 3cd496c8acb8..c9ec5c76c438 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1114,6 +1114,12 @@ struct kvm_arch {
bool exception_payload_enabled;
bool bus_lock_detection_enabled;
+ /*
+ * If exit_on_emulation_error is set, and the in-kernel instruction
+ * emulator fails to emulate an instruction, allow userspace
+ * the opportunity to look at it.
+ */
+ bool exit_on_emulation_error;
/* Deflect RDMSR and WRMSR to user space when they trigger a #GP */
u32 user_space_msr_mask;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a7c7b2b28de7..17468d983fbd 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4010,6 +4010,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
#endif
case KVM_CAP_VM_COPY_ENC_CONTEXT_FROM:
case KVM_CAP_SREGS2:
+ case KVM_CAP_EXIT_ON_EMULATION_FAILURE:
r = 1;
break;
case KVM_CAP_EXIT_HYPERCALL:
@@ -5649,6 +5650,13 @@ split_irqchip_unlock:
kvm->arch.hypercall_exit_enabled = cap->args[0];
r = 0;
break;
+ case KVM_CAP_EXIT_ON_EMULATION_FAILURE:
+ r = -EINVAL;
+ if (cap->args[0] & ~1)
+ break;
+ kvm->arch.exit_on_emulation_error = cap->args[0];
+ r = 0;
+ break;
default:
r = -EINVAL;
break;
@@ -7444,8 +7452,33 @@ void kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq, int inc_eip)
}
EXPORT_SYMBOL_GPL(kvm_inject_realmode_interrupt);
+static void prepare_emulation_failure_exit(struct kvm_vcpu *vcpu)
+{
+ struct x86_emulate_ctxt *ctxt = vcpu->arch.emulate_ctxt;
+ u32 insn_size = ctxt->fetch.end - ctxt->fetch.data;
+ struct kvm_run *run = vcpu->run;
+
+ run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
+ run->emulation_failure.suberror = KVM_INTERNAL_ERROR_EMULATION;
+ run->emulation_failure.ndata = 0;
+ run->emulation_failure.flags = 0;
+
+ if (insn_size) {
+ run->emulation_failure.ndata = 3;
+ run->emulation_failure.flags |=
+ KVM_INTERNAL_ERROR_EMULATION_FLAG_INSTRUCTION_BYTES;
+ run->emulation_failure.insn_size = insn_size;
+ memset(run->emulation_failure.insn_bytes, 0x90,
+ sizeof(run->emulation_failure.insn_bytes));
+ memcpy(run->emulation_failure.insn_bytes,
+ ctxt->fetch.data, insn_size);
+ }
+}
+
static int handle_emulation_failure(struct kvm_vcpu *vcpu, int emulation_type)
{
+ struct kvm *kvm = vcpu->kvm;
+
++vcpu->stat.insn_emulation_fail;
trace_kvm_emulate_insn_failed(vcpu);
@@ -7454,10 +7487,9 @@ static int handle_emulation_failure(struct kvm_vcpu *vcpu, int emulation_type)
return 1;
}
- if (emulation_type & EMULTYPE_SKIP) {
- vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
- vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION;
- vcpu->run->internal.ndata = 0;
+ if (kvm->arch.exit_on_emulation_error ||
+ (emulation_type & EMULTYPE_SKIP)) {
+ prepare_emulation_failure_exit(vcpu);
return 0;
}
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index f1ba602260f6..68c9e6d8bbda 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -280,6 +280,9 @@ struct kvm_xen_exit {
/* Encounter unexpected vm-exit reason */
#define KVM_INTERNAL_ERROR_UNEXPECTED_EXIT_REASON 4
+/* Flags that describe what fields in emulation_failure hold valid data. */
+#define KVM_INTERNAL_ERROR_EMULATION_FLAG_INSTRUCTION_BYTES (1ULL << 0)
+
/* for KVM_RUN, returned by mmap(vcpu_fd, offset=0) */
struct kvm_run {
/* in */
@@ -383,6 +386,25 @@ struct kvm_run {
__u32 ndata;
__u64 data[16];
} internal;
+ /*
+ * KVM_INTERNAL_ERROR_EMULATION
+ *
+ * "struct emulation_failure" is an overlay of "struct internal"
+ * that is used for the KVM_INTERNAL_ERROR_EMULATION sub-type of
+ * KVM_EXIT_INTERNAL_ERROR. Note, unlike other internal error
+ * sub-types, this struct is ABI! It also needs to be backwards
+ * compatible with "struct internal". Take special care that
+ * "ndata" is correct, that new fields are enumerated in "flags",
+ * and that each flag enumerates fields that are 64-bit aligned
+ * and sized (so that ndata+internal.data[] is valid/accurate).
+ */
+ struct {
+ __u32 suberror;
+ __u32 ndata;
+ __u64 flags;
+ __u8 insn_size;
+ __u8 insn_bytes[15];
+ } emulation_failure;
/* KVM_EXIT_OSI */
struct {
__u64 gprs[32];
@@ -1088,6 +1110,7 @@ struct kvm_ppc_resize_hpt {
#define KVM_CAP_EXIT_HYPERCALL 201
#define KVM_CAP_PPC_RPT_INVALIDATE 202
#define KVM_CAP_BINARY_STATS_FD 203
+#define KVM_CAP_EXIT_ON_EMULATION_FAILURE 204
#ifdef KVM_CAP_IRQ_ROUTING