KVM: x86: Exit to userspace on emulation skip failure (738fece4) · Commits · 戴 / test

Kill a few birds with one stone by forcing an exit to userspace on skip emulation failure. This removes a reference to EMULATE_FAIL, fixes a bug in handle_ept_misconfig() where it would exit to userspace without setting run->exit_reason, and fixes a theoretical bug in SVM's task_switch_interception() where it would overwrite run->exit_reason on a return of EMULATE_USER_EXIT. Note, this technically doesn't fully fix task_switch_interception() as it now incorrectly handles EMULATE_FAIL, but in practice there is no bug as EMULATE_FAIL will never be returned for EMULTYPE_SKIP. Signed-off-by:

Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by:

Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/svm.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -3885,8 +3885,8 @@ static int task_switch_interception(struct vcpu_svm *svm)
		int_type == SVM_EXITINTINFO_TYPE_SOFT \|\|
		(int_type == SVM_EXITINTINFO_TYPE_EXEPT &&
		(int_vec == OF_VECTOR \|\| int_vec == BP_VECTOR))) {
		if (skip_emulated_instruction(&svm->vcpu) != EMULATE_DONE)
		goto fail;
		if (skip_emulated_instruction(&svm->vcpu) == EMULATE_USER_EXIT)
		return 0;
		}

		if (int_type != SVM_EXITINTINFO_TYPE_SOFT)

arch/x86/kvm/x86.c

+7 −2

Original line number	Diff line number	Diff line
		@@ -6306,6 +6306,13 @@ static int handle_emulation_failure(struct kvm_vcpu *vcpu, int emulation_type)
		return EMULATE_DONE;
		}

		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;
		return EMULATE_USER_EXIT;
		}

		kvm_queue_exception(vcpu, UD_VECTOR);

		if (!is_guest_mode(vcpu) && kvm_x86_ops->get_cpl(vcpu) == 0) {
		@@ -6641,8 +6648,6 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu,
		inject_emulated_exception(vcpu);
		return EMULATE_DONE;
		}
		if (emulation_type & EMULTYPE_SKIP)
		return EMULATE_FAIL;
		return handle_emulation_failure(vcpu, emulation_type);
		}
		}

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