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

[Kang, Luwei]

> >  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.
     For precise_ip, it is the precise level in perf and set by perf command line in KVM guest, this may not reflect the accurate value (can be 0~3) here. Here set to 1 is used to allocate a counter for PEBS event and set the MSR_IA32_PEBS_ENABLE register. For PMU virtualization, KVM will trap the guest's write operation to PMU registers and allocate/free event counter from host if a counter enable/disable in guest. We can't always deduce the exact parameter of perf command line from the value of the guest writers to the register.

Thanks,
Luwei Kang