RE: [PATCH v1 3/8] KVM: x86: Allocate performance counter for PEBS event

[Alexander Shishkin]

"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?

Regards,
--
Alex