On Wed, Oct 30, 2019 at 08:42:10AM +0200, Alexander Shishkin wrote:
> "Kang, Luwei" <luwei.kang@xxxxxxxxx> writes:
>
> >> > static void pmc_reprogram_counter(struct kvm_pmc *pmc, u32 type,
> >> > unsigned config, bool exclude_user,
> >> > bool exclude_kernel, bool intr,
> >> > - bool in_tx, bool in_tx_cp)
> >> > + bool in_tx, bool in_tx_cp, bool pebs)
> >> > {
> >> > struct perf_event *event;
> >> > struct perf_event_attr attr = {
> >> > @@ -111,9 +111,12 @@ static void pmc_reprogram_counter(struct kvm_pmc *pmc, u32 type,
> >> > .exclude_user = exclude_user,
> >> > .exclude_kernel = exclude_kernel,
> >> > .config = config,
> >> > + .precise_ip = pebs ? 1 : 0,
> >> > + .aux_output = pebs ? 1 : 0,
> >>
> >> srsly?
> >
> > Hi Peter,
> > Thanks for review. For aux_output, I think it should be set 1 when the guest wants to enabled PEBS by Intel PT.
>
> attr.aux_output==1 means your group leader should be an intel_pt event
> for this to succeed. Luckily for this instance,
> perf_event_create_kernel_counter() doesn't actually check the
> attr.aux_output.
>
> Also, does 'bool pebs' mean PEBS-via-PT or just a PEBS counter? Or does
> it mean that in kvm it's the same thing?
It means pebs-over-pt, they only allow pebs if the output to pt bit is
set.
