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

[Alexander Graf]

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

Paolo, do you have any strong opinion here?


Alex