On Wed, 2018-03-07 at 16:19 +0100, Paolo Bonzini wrote:
> 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,
What about adding kvm_fast_pio() to also avoid duplication of branching
on 'in' versus 'out'? That seems worthy of a v2.
>
> 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
> >
