On 06/03/2018 21:58, Sean Christopherson wrote:
> Fast emulation of processor I/O for IN was disabled on x86 (both VMX
> and SVM) some years ago due to a buggy implementation. The addition
> of kvm_fast_pio_in(), used by SVM, re-introduced (functional!) fast
> emulation of IN. Piggyback SVM's work and use kvm_fast_pio_in() on
> VMX instead of performing full emulation of IN.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
There's a little code duplication that would be nice to avoid, moving
kvm_skip_emulated_instruction to kvm_fast_pio_{in,out}. Otherwise,
Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Paolo
> ---
> arch/x86/kvm/vmx.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 051dab74e4e9..c8a8391e95e5 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -6231,15 +6231,15 @@ static int handle_io(struct kvm_vcpu *vcpu)
>
> exit_qualification = vmcs_readl(EXIT_QUALIFICATION);
> string = (exit_qualification & 16) != 0;
> - in = (exit_qualification & 8) != 0;
>
> ++vcpu->stat.io_exits;
>
> - if (string || in)
> + if (string)
> return emulate_instruction(vcpu, 0) == EMULATE_DONE;
>
> port = exit_qualification >> 16;
> size = (exit_qualification & 7) + 1;
> + in = (exit_qualification & 8) != 0;
>
> ret = kvm_skip_emulated_instruction(vcpu);
>
> @@ -6247,7 +6247,10 @@ static int handle_io(struct kvm_vcpu *vcpu)
> * TODO: we might be squashing a KVM_GUESTDBG_SINGLESTEP-triggered
> * KVM_EXIT_DEBUG here.
> */
> - return kvm_fast_pio_out(vcpu, size, port) && ret;
> + if (in)
> + return kvm_fast_pio_in(vcpu, size, port) && ret;
> + else
> + return kvm_fast_pio_out(vcpu, size, port) && ret;
> }
>
> static void
>
