Re: [PATCH v2 2/6] KVM: x86/mmu: Fix use of enums in trace_fast_page_fault

[David Matlack <dmatlack@google.com>]

On Mon, Jul 12, 2021 at 09:14:01AM -0700, Ben Gardon wrote:
> On Wed, Jun 30, 2021 at 2:48 PM David Matlack <dmatlack@google.com> wrote:
> >
> > Enum values have to be exported to userspace since the formatting is not
> > done in the kernel. Without doing this perf maps RET_PF_FIXED and
> > RET_PF_SPURIOUS to 0, which results in incorrect output:
> >
> >   $ perf record -a -e kvmmmu:fast_page_fault --filter "ret==3" -- ./access_tracking_perf_test
> >   $ perf script | head -1
> >    [...] new 610006048d25877 spurious 0 fixed 0  <------ should be 1
> >
> > Fix this by exporting the enum values to userspace with TRACE_DEFINE_ENUM.
> >
> > Fixes: c4371c2a682e ("KVM: x86/mmu: Return unique RET_PF_* values if the fault was fixed")
> > Signed-off-by: David Matlack <dmatlack@google.com>
> > ---
> >  arch/x86/kvm/mmu/mmutrace.h | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/arch/x86/kvm/mmu/mmutrace.h b/arch/x86/kvm/mmu/mmutrace.h
> > index efbad33a0645..55c7e0fcda52 100644
> > --- a/arch/x86/kvm/mmu/mmutrace.h
> > +++ b/arch/x86/kvm/mmu/mmutrace.h
> > @@ -244,6 +244,9 @@ TRACE_EVENT(
> >                   __entry->access)
> >  );
> >
> > +TRACE_DEFINE_ENUM(RET_PF_FIXED);
> > +TRACE_DEFINE_ENUM(RET_PF_SPURIOUS);
> > +
> 
> If you're planning to send out a v3 anyway, it might be worth adding
> all the PF return code enums:
> 
> enum {
> RET_PF_RETRY = 0,
> RET_PF_EMULATE,
> RET_PF_INVALID,
> RET_PF_FIXED,
> RET_PF_SPURIOUS,
> };
> 
> Just so that no one has to worry about this in the future.

Will do in v3. Thanks.

> 
> >  TRACE_EVENT(
> >         fast_page_fault,
> >         TP_PROTO(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, u32 error_code,
> > --
> > 2.32.0.93.g670b81a890-goog
> >