kvm: x86: Add "last CPU" to some KVM_EXIT information

More often than not, a failed VM-entry in an x86 production
environment is induced by a defective CPU. To help identify the bad
hardware, include the id of the last logical CPU to run a vCPU in the
information provided to userspace on a KVM exit for failed VM-entry or
for KVM internal errors not associated with emulation. The presence of
this additional information is indicated by a new capability,
KVM_CAP_LAST_CPU.

Signed-off-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Oliver Upton <oupton@google.com>
Reviewed-by: Peter Shier <pshier@google.com>
Message-Id: <20200603235623.245638-5-jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 426f945..1cfe79b 100644 (file)
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -4794,6 +4794,7 @@ hardware_exit_reason.
                /* KVM_EXIT_FAIL_ENTRY */
                struct {
                        __u64 hardware_entry_failure_reason;
+                       __u32 cpu; /* if KVM_LAST_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/svm.c b/arch/x86/kvm/svm/svm.c
index 24b7f32..8ecd46f 100644 (file)
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2947,6 +2947,7 @@ static int handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
                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 = svm->last_cpu;
                dump_vmcb(vcpu);
                return 0;
        }
@@ -2970,8 +2971,9 @@ static int handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
                vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
                vcpu->run->internal.suberror =
                        KVM_INTERNAL_ERROR_UNEXPECTED_EXIT_REASON;
-               vcpu->run->internal.ndata = 1;
+               vcpu->run->internal.ndata = 2;
                vcpu->run->internal.data[0] = exit_code;
+               vcpu->run->internal.data[1] = svm->last_cpu;
                return 0;
        }
 

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 4d8f12c..b52bceb 100644 (file)
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -4781,10 +4781,11 @@ static int handle_exception_nmi(struct kvm_vcpu *vcpu)
            !(is_page_fault(intr_info) && !(error_code & PFERR_RSVD_MASK))) {
                vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
                vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_SIMUL_EX;
-               vcpu->run->internal.ndata = 3;
+               vcpu->run->internal.ndata = 4;
                vcpu->run->internal.data[0] = vect_info;
                vcpu->run->internal.data[1] = intr_info;
                vcpu->run->internal.data[2] = error_code;
+               vcpu->run->internal.data[3] = vmx->last_cpu;
                return 0;
        }
 
@@ -6006,6 +6007,7 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
                vcpu->run->exit_reason = KVM_EXIT_FAIL_ENTRY;
                vcpu->run->fail_entry.hardware_entry_failure_reason
                        = exit_reason;
+               vcpu->run->fail_entry.cpu = vmx->last_cpu;
                return 0;
        }
 
@@ -6014,6 +6016,7 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
                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 = vmx->last_cpu;
                return 0;
        }
 
@@ -6040,6 +6043,8 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
                        vcpu->run->internal.data[3] =
                                vmcs_read64(GUEST_PHYSICAL_ADDRESS);
                }
+               vcpu->run->internal.data[vcpu->run->internal.ndata++] =
+                       vmx->last_cpu;
                return 0;
        }
 
@@ -6095,8 +6100,9 @@ unexpected_vmexit:
        vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
        vcpu->run->internal.suberror =
                        KVM_INTERNAL_ERROR_UNEXPECTED_EXIT_REASON;
-       vcpu->run->internal.ndata = 1;
+       vcpu->run->internal.ndata = 2;
        vcpu->run->internal.data[0] = exit_reason;
+       vcpu->run->internal.data[1] = vmx->last_cpu;
        return 0;
 }
 

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 82f457f..1a0fad1 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3510,6 +3510,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
        case KVM_CAP_MSR_PLATFORM_INFO:
        case KVM_CAP_EXCEPTION_PAYLOAD:
        case KVM_CAP_SET_GUEST_DEBUG:
+       case KVM_CAP_LAST_CPU:
                r = 1;
                break;
        case KVM_CAP_SYNC_REGS:

diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 4fdf303..ff9b335 100644 (file)
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -289,6 +289,7 @@ struct kvm_run {
                /* KVM_EXIT_FAIL_ENTRY */
                struct {
                        __u64 hardware_entry_failure_reason;
+                       __u32 cpu;
                } fail_entry;
                /* KVM_EXIT_EXCEPTION */
                struct {
@@ -1031,6 +1032,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_PPC_SECURE_GUEST 181
 #define KVM_CAP_HALT_POLL 182
 #define KVM_CAP_ASYNC_PF_INT 183
+#define KVM_CAP_LAST_CPU 184
 
 #ifdef KVM_CAP_IRQ_ROUTING