Commit 1aa561b1 authored by Jim Mattson's avatar Jim Mattson Committed by Paolo Bonzini
Browse files

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: default avatarJim Mattson <jmattson@google.com>
Reviewed-by: default avatarOliver Upton <oupton@google.com>
Reviewed-by: default avatarPeter Shier <pshier@google.com>
Message-Id: <20200603235623.245638-5-jmattson@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 80a1684c

Documentation/virt/kvm/api.rst

+1 −0
Original line number Diff line number Diff line
@@ -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

arch/x86/kvm/svm/svm.c

+3 −1
Original line number Diff line number Diff line
@@ -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;

	}

arch/x86/kvm/vmx/vmx.c

+8 −2
Original line number Diff line number Diff line
@@ -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 @@ static int vmx_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_reason;

	vcpu->run->internal.data[1] = vmx->last_cpu;

	return 0;

}

arch/x86/kvm/x86.c

+1 −0
Original line number Diff line number Diff line
@@ -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:

include/uapi/linux/kvm.h

+2 −0
Original line number Diff line number Diff line
@@ -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