On 05/11/2017 15:21, Liran Alon wrote:
> From: Liran Alon <liran.alon@xxxxxxxxxxxxxxxxxx>
>
> On this case, handle_emulation_failure() fills kvm_run with
> internal-error information which it expects to be delivered
> to user-mode for further processing.
> However, the code reports a wrong return-value which makes KVM to never
> return to user-mode on this scenario.
>
> Fixes: 6d77dbfc88e3 ("KVM: inject #UD if instruction emulation fails and exit to
> userspace")
>
> Signed-off-by: Liran Alon <liran.alon@xxxxxxxxxx>
> Reviewed-by: Nikita Leshenko <nikita.leshchenko@xxxxxxxxxx>
> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> ---
> arch/x86/kvm/x86.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 03869eb7fcd6..f4edb4baf441 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -5413,7 +5413,7 @@ static int handle_emulation_failure(struct kvm_vcpu *vcpu)
> vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
> vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION;
> vcpu->run->internal.ndata = 0;
> - r = EMULATE_FAIL;
> + r = EMULATE_USER_EXIT;
> }
> kvm_queue_exception(vcpu, UD_VECTOR);
>
>
You should still get an emulation failure when the emulator is invoked
by mmu.c:
case EMULATE_USER_EXIT:
++vcpu->stat.mmio_exits;
/* fall through */
case EMULATE_FAIL:
return 0;
What is the caller of x86_emulate_instruction that you are interested
in? #UD is not affected, because emulation_type has EMULTYPE_TRAP_UD
set and therefore x86_emulate_instruction exits before invoking
handle_emulation_failure.
Thanks,
Paolo
