Re: [PATCH v2 1/3] KVM: X86: Trace vcpu_id for vmexit

[Peter Xu <peterx@redhat.com>]

On Wed, Sep 04, 2019 at 10:26:58AM -0700, Sean Christopherson wrote:
> On Thu, Aug 15, 2019 at 06:34:56PM +0800, Peter Xu wrote:
> > Tracing the ID helps to pair vmenters and vmexits for guests with
> > multiple vCPUs.
> > 
> > Reviewed-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>
> > Signed-off-by: Peter Xu <peterx@redhat.com>
> > ---
> >  arch/x86/kvm/trace.h | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
> > index b5c831e79094..c682f3f7f998 100644
> > --- a/arch/x86/kvm/trace.h
> > +++ b/arch/x86/kvm/trace.h
> > @@ -232,17 +232,20 @@ TRACE_EVENT(kvm_exit,
> >  		__field(	u32,	        isa             )
> >  		__field(	u64,	        info1           )
> >  		__field(	u64,	        info2           )
> > +		__field(	int,	        vcpu_id         )
> 
> It doesn't actually affect anything, but vcpu_id is stored and printed as
> an 'unsigned int' everywhere else in the trace code.  Stylistically I like
> that approach even though struct kvm_vcpu holds it as a signed int.

True.  I can switch to unsigned int to get aligned with the rest if
there's other comment to address.  Though from codebase-wise I would
even prefer signed because it gives us a chance to set an invalid vcpu
id (-1) where necessary, or notice something severly wrong when <-1.
After all it should far cover our usage (IIUC max vcpu id should be
512 cross archs).

Thanks,

-- 
Peter Xu