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From:   Alexander Shishkin <alexander.shishkin@linux.intel.com>
To:     "Kang\, Luwei" <luwei.kang@intel.com>,
        Peter Zijlstra <peterz@infradead.org>
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Subject: RE: [PATCH v1 3/8] KVM: x86: Allocate performance counter for PEBS event
In-Reply-To: <82D7661F83C1A047AF7DC287873BF1E173835B1A@SHSMSX104.ccr.corp.intel.com>
References: <1572217877-26484-1-git-send-email-luwei.kang@intel.com> <1572217877-26484-4-git-send-email-luwei.kang@intel.com> <20191029144612.GK4097@hirez.programming.kicks-ass.net> <82D7661F83C1A047AF7DC287873BF1E173835B1A@SHSMSX104.ccr.corp.intel.com>
Date:   Wed, 30 Oct 2019 08:42:10 +0200
Message-ID: <87o8xyg2f1.fsf@ashishki-desk.ger.corp.intel.com>
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"Kang, Luwei" <luwei.kang@intel.com> 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