Re: Tracing KVM with Systemtap

Stefan Hajnoczi
2010-09-22T13:39:38Z

On Wed, Sep 22, 2010 at 1:42 PM, Rayson Ho <rho@redhat.com> wrote:
> On Wed, 2010-09-22 at 13:33 +0100, Stefan Hajnoczi wrote:
>> KVM does not generate code.  Almost all the "emulation" code in the
>> source tree is part of the Tiny Code Generator (TCG) used when KVM is
>> not enabled (e.g. to emulate an ARM board on an x86-64 host).
>
> Thanks, that's what I thought too. Otherwise it would be really slow to
> run KVM :)
>
> But if KVM is not used, and QEMU host & guest are running on the same
> architecture, is TCG off? (Hmm, I guess I can find that answer myself by
> reading the code).

TCG is unused when KVM is enabled. There has been discussion about
building without it for KVM-only builds and qemu-kvm.git can do that
today with a ./configure option.

> Stefan, are you accepting patches? If so, I will create a patch with the
> Systemtap framework & other probes.

I am not a qemu.git or qemu-kvm.git committer but I review patches in
areas that I work in, like tracing. I'll be happy to give you
feedback.

Stefan