From mboxrd@z Thu Jan 1 00:00:00 1970 From: Will Deacon Subject: Re: [PATCH v3 6/9] kvm: arm/arm64: Add host pmu to support VM introspection Date: Wed, 18 Jan 2017 13:45:58 +0000 Message-ID: <20170118134558.GF28063@arm.com> References: <20170110113856.7183-1-punit.agrawal@arm.com> <20170110113856.7183-7-punit.agrawal@arm.com> <1a6b8d71-58a5-b29b-3f01-e945deb2baf6@arm.com> <20170118113523.GB3231@leverpostej> <87o9z4msi3.fsf@e105922-lin.cambridge.arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org, Marc Zyngier , linux-kernel@vger.kernel.org, Steven Rostedt , Peter Zijlstra , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org To: Punit Agrawal Return-path: Content-Disposition: inline In-Reply-To: <87o9z4msi3.fsf@e105922-lin.cambridge.arm.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu List-Id: kvm.vger.kernel.org On Wed, Jan 18, 2017 at 01:01:40PM +0000, Punit Agrawal wrote: > Mark Rutland 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. Will