From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752360AbdARNsH (ORCPT ); Wed, 18 Jan 2017 08:48:07 -0500 Received: from foss.arm.com ([217.140.101.70]:53616 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751691AbdARNsG (ORCPT ); Wed, 18 Jan 2017 08:48:06 -0500 Date: Wed, 18 Jan 2017 13:45:58 +0000 From: Will Deacon To: Punit Agrawal Cc: Mark Rutland , Marc Zyngier , kvm@vger.kernel.org, Peter Zijlstra , linux-kernel@vger.kernel.org, Steven Rostedt , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu Subject: Re: [PATCH v3 6/9] kvm: arm/arm64: Add host pmu to support VM introspection 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-Disposition: inline In-Reply-To: <87o9z4msi3.fsf@e105922-lin.cambridge.arm.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@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