linux-kernel - Re: [PATCH v4 04/38] perf: Add a EVENT

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Message-ID: <800f99f6-a1bf-41f3-bc65-67fbe4c61368@linux.intel.com>
Date: Tue, 20 May 2025 14:50:27 -0400
From: "Liang, Kan" <kan.liang@...ux.intel.com>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Mingwei Zhang <mizhang@...gle.com>, Peter Zijlstra
 <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 Arnaldo Carvalho de Melo <acme@...nel.org>,
 Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini
 <pbonzini@...hat.com>, Mark Rutland <mark.rutland@....com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
 Adrian Hunter <adrian.hunter@...el.com>, Liang@...gle.com,
 "H. Peter Anvin" <hpa@...or.com>, linux-perf-users@...r.kernel.org,
 linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
 linux-kselftest@...r.kernel.org, Yongwei Ma <yongwei.ma@...el.com>,
 Xiong Zhang <xiong.y.zhang@...ux.intel.com>,
 Dapeng Mi <dapeng1.mi@...ux.intel.com>, Jim Mattson <jmattson@...gle.com>,
 Sandipan Das <sandipan.das@....com>, Zide Chen <zide.chen@...el.com>,
 Eranian Stephane <eranian@...gle.com>, Shukla Manali
 <Manali.Shukla@....com>, Nikunj Dadhania <nikunj.dadhania@....com>
Subject: Re: [PATCH v4 04/38] perf: Add a EVENT_GUEST flag

On 2025-05-20 1:51 p.m., Namhyung Kim wrote:
>>>> @@ -1089,6 +1094,7 @@ struct bpf_perf_event_data_kern {
>>>>   */
>>>>  struct perf_cgroup_info {
>>>>  	struct perf_time_ctx		time;
>>>> +	struct perf_time_ctx		timeguest;
>>>>  	int				active;
>>>>  };
>>>>  
>>>> diff --git a/kernel/events/core.c b/kernel/events/core.c
>>>> index e38c8b5e8086..7a2115b2c5c1 100644
>>>> --- a/kernel/events/core.c
>>>> +++ b/kernel/events/core.c
>>>> @@ -163,7 +163,8 @@ enum event_type_t {
>>>>  	/* see ctx_resched() for details */
>>>>  	EVENT_CPU	= 0x10,
>>>>  	EVENT_CGROUP	= 0x20,
>>>> -	EVENT_FLAGS	= EVENT_CGROUP,
>>>> +	EVENT_GUEST	= 0x40,
>>> It's not clear to me if this flag is for events to include guests or
>>> exclude them.  Can you please add a comment?
>>>
>> /*
>>  * There are guest events. The for_each_epc() iteration can
>>  * skip those PMUs which doesn't support guest events via the
>>  * MEDIATED_VPMU. It is also used to indicate the start/end of
>>  * guest events to calculate the guest running time.
>>  */
> Thanks for the explanation.  So it's for events with !exclude_guest on
> host 

The above "guest events" means that the events in a guest. The KVM
should only invokes the interface when a guest requires PMU.

For the host, for now, only the event with exclude_guest is supported.
The !exclude_guest event on host must be failed to be created if there
is a running VM.

and to do some operation only for host-only events on mediated
> vPMUs.

Yes.

Update the comments as below.

/*
 * There are events in a guest enabled with MEDIATED_VPMU.
 * The flag can be used in two places.
 * - The for_each_epc() iteration can skip those PMUs which
 *   doesn't support the events in a guest via the MEDIATED_VPMU.
 * - Indicate the start/end point of the events in a guest.
 *   The guest running time can be deducted for the
 *   host-only (exclude_guest) events.
 */

Thanks,
Kan