> On 14 Dec 2019, at 2:20, Jim Mattson <jmattson@xxxxxxxxxx> wrote:
>
> More often than not, a failed VM-entry in a production environment is
> the result of a defective CPU (at least, insofar as Intel x86 is
> concerned). To aid in identifying the bad hardware, add the logical
> CPU to the information provided to userspace on a KVM exit with reason
> KVM_EXIT_FAIL_ENTRY. The presence of this additional information is
> indicated by a new capability, KVM_CAP_FAILED_ENTRY_CPU.
>
> Signed-off-by: Jim Mattson <jmattson@xxxxxxxxxx>
> Reviewed-by: Oliver Upton <oupton@xxxxxxxxxx>
> Cc: Liran Alon <liran.alon@xxxxxxxxxx>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Reviewed-by: Liran Alon <liran.alon@xxxxxxxxxx>
BTW, one could argue that receiving an unexpected exit-reason (i.e. KVM_INTERNAL_ERROR_UNEXPECTED_EXIT_REASON)
could also only occur in production either from a KVM bug or from a defective CPU. Similar to failed VM-entry.
Should we add similar behaviour to that as-well?
-Liran
> ---
> Documentation/virt/kvm/api.txt | 1 +
> arch/x86/kvm/svm.c | 1 +
> arch/x86/kvm/vmx/vmx.c | 2 ++
> arch/x86/kvm/x86.c | 1 +
> include/uapi/linux/kvm.h | 2 ++
> 5 files changed, 7 insertions(+)
>
> diff --git a/Documentation/virt/kvm/api.txt b/Documentation/virt/kvm/api.txt
> index ebb37b34dcfc..6e5d92406b65 100644
> --- a/Documentation/virt/kvm/api.txt
> +++ b/Documentation/virt/kvm/api.txt
> @@ -4245,6 +4245,7 @@ hardware_exit_reason.
> /* KVM_EXIT_FAIL_ENTRY */
> struct {
> __u64 hardware_entry_failure_reason;
> + __u32 cpu; /* if KVM_CAP_FAILED_ENTRY_CPU */
> } fail_entry;
>
> If exit_reason is KVM_EXIT_FAIL_ENTRY, the vcpu could not be run due
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 122d4ce3b1ab..e07c5ce3ac93 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -4980,6 +4980,7 @@ static int handle_exit(struct kvm_vcpu *vcpu)
> kvm_run->exit_reason = KVM_EXIT_FAIL_ENTRY;
> kvm_run->fail_entry.hardware_entry_failure_reason
> = svm->vmcb->control.exit_code;
> + kvm_run->fail_entry.cpu = vcpu->cpu;
> dump_vmcb(vcpu);
> return 0;
> }
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index e3394c839dea..17d1a1676fc0 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -5846,6 +5846,7 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu)
> vcpu->run->exit_reason = KVM_EXIT_FAIL_ENTRY;
> vcpu->run->fail_entry.hardware_entry_failure_reason
> = exit_reason;
> + vcpu->run->fail_entry.cpu = vcpu->cpu;
> return 0;
> }
>
> @@ -5854,6 +5855,7 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu)
> vcpu->run->exit_reason = KVM_EXIT_FAIL_ENTRY;
> vcpu->run->fail_entry.hardware_entry_failure_reason
> = vmcs_read32(VM_INSTRUCTION_ERROR);
> + vcpu->run->fail_entry.cpu = vcpu->cpu;
> return 0;
> }
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index cf917139de6b..9e89a32056d1 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -3273,6 +3273,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> case KVM_CAP_GET_MSR_FEATURES:
> case KVM_CAP_MSR_PLATFORM_INFO:
> case KVM_CAP_EXCEPTION_PAYLOAD:
> + case KVM_CAP_FAILED_ENTRY_CPU:
> r = 1;
> break;
> case KVM_CAP_SYNC_REGS:
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index f0a16b4adbbd..09ba7174456d 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -277,6 +277,7 @@ struct kvm_run {
> /* KVM_EXIT_FAIL_ENTRY */
> struct {
> __u64 hardware_entry_failure_reason;
> + __u32 cpu;
> } fail_entry;
> /* KVM_EXIT_EXCEPTION */
> struct {
> @@ -1009,6 +1010,7 @@ struct kvm_ppc_resize_hpt {
> #define KVM_CAP_PPC_GUEST_DEBUG_SSTEP 176
> #define KVM_CAP_ARM_NISV_TO_USER 177
> #define KVM_CAP_ARM_INJECT_EXT_DABT 178
> +#define KVM_CAP_FAILED_ENTRY_CPU 179
>
> #ifdef KVM_CAP_IRQ_ROUTING
>
> --
> 2.24.1.735.g03f4e72817-goog
>
