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From: Punit Agrawal <punit.agrawal@arm.com>
To: Will Deacon <will.deacon@arm.com>
Cc: kvm@vger.kernel.org, Marc Zyngier <marc.zyngier@arm.com>,
	linux-kernel@vger.kernel.org,
	Steven Rostedt <rostedt@goodmis.org>,
	Peter Zijlstra <peterz@infradead.org>,
	kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 6/9] kvm: arm/arm64: Add host pmu to support VM introspection
Date: Wed, 18 Jan 2017 14:58:20 +0000	[thread overview]
Message-ID: <87bmv4mn3n.fsf@e105922-lin.cambridge.arm.com> (raw)
In-Reply-To: <20170118134558.GF28063@arm.com> (Will Deacon's message of "Wed, 18 Jan 2017 13:45:58 +0000")

Will Deacon <will.deacon@arm.com> writes:

> On Wed, Jan 18, 2017 at 01:01:40PM +0000, Punit Agrawal wrote:
>> Mark Rutland <mark.rutland@arm.com> writes:
>> 
>> > On Wed, Jan 18, 2017 at 11:21:21AM +0000, Marc Zyngier wrote:
>> >> On 10/01/17 11:38, Punit Agrawal wrote:
>> >> > +#define VM_MASK	GENMASK_ULL(31, 0)
>> >> > +#define EVENT_MASK	GENMASK_ULL(32, 39)
>> >> > +#define EVENT_SHIFT	(32)
>> >> > +
>> >> > +#define to_pid(cfg)	((cfg) & VM_MASK)
>> >> > +#define to_event(cfg)	(((cfg) & EVENT_MASK) >> EVENT_SHIFT)
>> >> > +
>> >> > +PMU_FORMAT_ATTR(vm, "config:0-31");
>> >> > +PMU_FORMAT_ATTR(event, "config:32-39");
>> >> 
>> >> I'm a bit confused by these. Can't you get the PID of the VM you're
>> >> tracing directly from perf, without having to encode things?
>> 
>> With perf attached to a PID, the event gets scheduled out when the task
>> is context switched. As the PID of the controlling process was used,
>> none of the vCPU events were counted.
>
> So it sounds like userspace needs to deal with this by attaching to the PIDs
> of the vCPUs. Given that perf kvm seems to have knowledge of vCPUs, it would
> be nice to know why that logic isn't reusable here. Take a look in
> tools/perf/builtin-kvm.c and if it's not up to the job, then perhaps it can
> be improved.

Thanks for the pointer. I'll have a play with perf kvm to see if it can
be leveraged here.

>
> Will
> _______________________________________________
> kvmarm mailing list
> kvmarm@lists.cs.columbia.edu
> https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

  reply	other threads:[~2017-01-18 14:58 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-01-10 11:38 [PATCH v3 0/9] Add support for monitoring guest TLB operations Punit Agrawal
2017-01-10 11:38 ` [PATCH v3 1/9] arm64/kvm: hyp: tlb: use __tlbi() helper Punit Agrawal
2017-01-10 11:38 ` [PATCH v3 2/9] KVM: Track the pid of the VM process Punit Agrawal
2017-01-10 11:38 ` [PATCH v3 3/9] KVM: Add event to trace tlb invalidations Punit Agrawal
2017-01-10 11:38 ` [PATCH v3 4/9] arm: KVM: Handle trappable TLB instructions Punit Agrawal
2017-01-10 11:38 ` [PATCH v3 5/9] arm64: " Punit Agrawal
2017-01-10 11:38 ` [PATCH v3 6/9] kvm: arm/arm64: Add host pmu to support VM introspection Punit Agrawal
2017-01-18 11:21   ` Marc Zyngier
2017-01-18 11:35     ` Mark Rutland
2017-01-18 13:01       ` Punit Agrawal
2017-01-18 13:18         ` Marc Zyngier
2017-01-18 14:51           ` Punit Agrawal
2017-01-18 15:17             ` Mark Rutland
2017-01-18 16:17               ` Punit Agrawal
2017-01-18 18:05                 ` Mark Rutland
2017-01-19 16:42                   ` Christoffer Dall
2017-01-23 11:21                     ` Punit Agrawal
2017-01-18 13:45         ` Will Deacon
2017-01-18 14:58           ` Punit Agrawal [this message]
2017-01-18 13:06     ` Punit Agrawal
2017-01-10 11:38 ` [PATCH v3 7/9] kvm: host_pmu: Add support for tracking guest TLB operations Punit Agrawal
2017-01-10 11:38 ` [PATCH v3 8/9] arm: KVM: Enable support for host pmu Punit Agrawal
2017-01-10 11:38 ` [PATCH v3 9/9] arm64: KVM: Enable support for the " Punit Agrawal

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