Re: [PATCH 1/5] kvm/x86: fix inversed check for async_pf MSR

[Roman Kagan <rkagan@virtuozzo.com>]

On Fri, Dec 02, 2016 at 04:14:48PM +0200, Mika Penttilä wrote:
> > On Fri, Dec 02, 2016 at 12:45:28PM +0200, Mika Penttilä wrote:
> > > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > > > index bf11fe4..14a46e9 100644
> > > > --- a/arch/x86/kvm/x86.c
> > > > +++ b/arch/x86/kvm/x86.c
> > > > @@ -8402,7 +8402,7 @@ void kvm_arch_async_page_present(struct kvm_vcpu *vcpu,
> > > > bool kvm_arch_can_inject_async_page_present(struct kvm_vcpu *vcpu)
> > > > {
> > > > 	if (!(vcpu->arch.apf.msr_val & KVM_ASYNC_PF_ENABLED))
> > > > -		return true;
> > > > +		return false;
> > > > 
> > > > 
> > > Why do you make this change?
> 
> > Because the code does the opposite of what it's meant to do.
> 
> It could have a better name but returning "true" is right. See below.
> 
>  > > I think kvm_arch_async_page_present() is not
> > > ever called now and neither kvm_del_async_pf_gfn(vcpu, work->arch.gfn);
> 
> > I wonder how you came to such a conclusion?  I certainly see them called
> > on my test machine (you need to have the guest memory swapped out for
> > that, that can be forced e.g. using a memory cgroup).
> 
> if !KVM_ASYNC_PF_ENABLED then kvm_check_async_pf_completion(), it's only call site, never calls it.

How's that?  I don't see any check for it in
kvm_check_async_pf_completion().  Moreover, that's exactly where it does
that check.

> Maybe you had KVM_ASYNC_PF_ENABLED?

Of course I did.  Not sure I get what you mean...

Roman.