Re: [PATCH v4 0/5] KVM: x86: Intel LBR related perf cleanups

[Sean Christopherson]

On Sat, Sep 17, 2022, Sean Christopherson wrote:
> On Thu, Sep 08, 2022, Peter Zijlstra wrote:
> > On Thu, Sep 01, 2022 at 05:32:53PM +0000, Sean Christopherson wrote:
> > 
> > > Sean Christopherson (5):
> > >   perf/x86/core: Remove unnecessary stubs provided for KVM-only helpers
> > >   perf/x86/core: Drop the unnecessary return value from
> > >     x86_perf_get_lbr()
> > >   KVM: VMX: Move vmx_get_perf_capabilities() definition to vmx.c
> > >   KVM: VMX: Fold vmx_supported_debugctl() into vcpu_supported_debugctl()
> > >   KVM: VMX: Advertise PMU LBRs if and only if perf supports LBRs
> > 
> > These look good to me; how do you want this routed, if through the KVM
> > tree:
> > 
> > Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> 
> Thanks!  If you don't anticipate conflicts in the perf headers, I'll take 'em
> through KVM, patch 01 introduced a new warning that I need to resolve (hopefully
> it doesn't throw a wrench into things).

Rats, patch 01 is flat out wrong.  The stubs for Intel and AMD are necessary
because KVM_{AMD,INTEL} don't strictly require CPU_SUP_{AMD/INTEL}.  KVM_AMD
doesn't have any CPU_SUP_* requirement (which probably should be fixed), and
KVM_INTEL effectively require INTEL || CENTAUR || ZHAOXIN.

x86_perf_get_lbr() can still be cleaned up to fix KVM's benign bug of not checking
the result by zeroing the structure when LBRs are unsupported.

v5 incoming...