Re: [Qemu-devel] [PATCH 6/6] kvm_stat: Add powerpc support

[Michael Ellerman]

On Wed, 2014-06-18 at 02:59 +0200, Alexander Graf wrote:
> On 18.06.14 02:50, Michael Ellerman wrote:
> > On Tue, 2014-06-17 at 10:27 +0200, Alexander Graf wrote:
> >> On 17.06.14 09:54, Michael Ellerman wrote:
> >>> Add support for powerpc platforms. We use uname -m, which allows us to
> >>> detect ppc, ppc64 and ppc64le/el.
> >>>
> >>> Signed-off-by: Michael Ellerman <address@hidden>
> >> Could you please add support for PR KVM tracepoints along the way? There
> >> we do know the exit reason for every single guest <-> host transition. I
> >> would like to move to a similar model with HV in the future, so we can
> >> hopefully just reuse this by then.
> > So I think what you're saying is you want it to somehow support using
> > 'kvm_exit' for PR and 'kvm_userspace_exit' for HV?
> 
> "kvm_userspace_exit" is implemented on both HV and PR. "kvm_exit" is PR 
> only, but I'm hoping we can get it working in HV as well.
> 
> > Or actually use 'kvm_exit' if it exists and fall back to 
> > 'kvm_userspace_exit',
> > so that if HV starts providing 'kvm_exit' the script will pick that up 
> > without
> > further changes.
> 
> They are completely different things. "kvm_userspace_exit" tells us 
> which exits we take from KVM -> QEMU. "kvm_exit" tells us which exits we 
> take from guest -> KVM.
>
> In fact, IIRC x86 also implements kvm_userspace_exit - or at least 
> something very similar to it. It's a completely separate category. 

Right. Everyone implements kvm_userspace_exit, it's in virt/kvm/kvm_main.c

> Maybe it should be a command line switch to distinguish between the count 
> types?

Or just we always read the kvm_userspace_exit counts, and if we find kvm_exit
we expose that as well - with an arch specific set of reasons.

cheers