Re: [PATCH] x86: events: Do not return bogus capabilities if PMU is broken

[Paolo Bonzini]

On 6/1/22 13:07, Peter Zijlstra wrote:
> On Wed, Jun 01, 2022 at 05:42:56AM -0400, Paolo Bonzini wrote:
> > From: Like Xu <likexu@xxxxxxxxxxx>
> >
> > If the PMU is broken due to firmware issues, check_hw_exists() will return
> > false but perf_get_x86_pmu_capability() will still return data from x86_pmu.
> > Likewise if some of the hotplug callbacks cannot be installed the contents
> > of x86_pmu will not be reverted.
> >
> > Handle the failure in both cases by clearing x86_pmu if init_hw_perf_events()
> > or reverts to software events only.
> >
> > Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
>
> No SoB from Like,

And hardly any code from him either except for a single memset, :) but 
I'll add

	Signed-off-by: Like Xu <likexu@xxxxxxxxxxx>
	Co-developed-by: Like Xu <likexu@xxxxxxxxxxx>

(I have hooks that notice this when pushing, but they don't help with 
git-send-email...).


> > @@ -2982,6 +2985,11 @@ unsigned long perf_misc_flags(struct pt_regs *regs)
> >   
> >   void perf_get_x86_pmu_capability(struct x86_pmu_capability *cap)
> >   {
> > +	if (!x86_pmu.name) {
>
> We have x86_pmu_initialized(), the implementation is a bit daft, but
> might as well use it here too, no?

Yes, thanks.

Paolo