Commit 7396d337 authored by Liran Alon's avatar Liran Alon Committed by Paolo Bonzini
Browse files

KVM: x86: Return to userspace with internal error on unexpected exit reason 



Receiving an unexpected exit reason from hardware should be considered
as a severe bug in KVM. Therefore, instead of just injecting #UD to
guest and ignore it, exit to userspace on internal error so that
it could handle it properly (probably by terminating guest).

In addition, prefer to use vcpu_unimpl() instead of WARN_ONCE()
as handling unexpected exit reason should be a rare unexpected
event (that was expected to never happen) and we prefer to print
a message on it every time it occurs to guest.

Furthermore, dump VMCS/VMCB to dmesg to assist diagnosing such cases.

Reviewed-by: default avatarMihai Carabas <mihai.carabas@oracle.com>
Reviewed-by: default avatarNikita Leshenko <nikita.leshchenko@oracle.com>
Reviewed-by: default avatarJoao Martins <joao.m.martins@oracle.com>
Signed-off-by: default avatarLiran Alon <liran.alon@oracle.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 1edce0a9

arch/x86/kvm/svm.c

+8 −3
Original line number Diff line number Diff line
@@ -4981,9 +4981,14 @@ static int handle_exit(struct kvm_vcpu *vcpu) 


	if (exit_code >= ARRAY_SIZE(svm_exit_handlers)

	    || !svm_exit_handlers[exit_code]) {

		WARN_ONCE(1, "svm: unexpected exit reason 0x%x\n", exit_code);

		kvm_queue_exception(vcpu, UD_VECTOR);

		return 1;

		vcpu_unimpl(vcpu, "svm: unexpected exit reason 0x%x\n", exit_code);

		dump_vmcb(vcpu);

		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.data[0] = exit_code;

		return 0;

	}



	return svm_exit_handlers[exit_code](svm);

arch/x86/kvm/vmx/vmx.c

+7 −2
Original line number Diff line number Diff line
@@ -5870,8 +5870,13 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu) 
	else {

		vcpu_unimpl(vcpu, "vmx: unexpected exit reason 0x%x\n",

				exit_reason);

		kvm_queue_exception(vcpu, UD_VECTOR);

		return 1;

		dump_vmcs();

		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.data[0] = exit_reason;

		return 0;

	}

}

include/uapi/linux/kvm.h

+2 −0
Original line number Diff line number Diff line
@@ -243,6 +243,8 @@ struct kvm_hyperv_exit { 
#define KVM_INTERNAL_ERROR_SIMUL_EX	2

/* Encounter unexpected vm-exit due to delivery event. */

#define KVM_INTERNAL_ERROR_DELIVERY_EV	3

/* Encounter unexpected vm-exit reason */

#define KVM_INTERNAL_ERROR_UNEXPECTED_EXIT_REASON	4



/* for KVM_RUN, returned by mmap(vcpu_fd, offset=0) */

struct kvm_run {

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