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[209.132.180.67]) by mx.google.com with ESMTP id c19si489360otp.3.2019.12.22.04.11.34; Sun, 22 Dec 2019 04:11:46 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726664AbfLVMK4 (ORCPT + 99 others); Sun, 22 Dec 2019 07:10:56 -0500 Received: from inca-roads.misterjones.org ([213.251.177.50]:36670 "EHLO inca-roads.misterjones.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726189AbfLVMK4 (ORCPT ); Sun, 22 Dec 2019 07:10:56 -0500 Received: from 78.163-31-62.static.virginmediabusiness.co.uk ([62.31.163.78] helo=big-swifty.misterjones.org) by cheepnis.misterjones.org with esmtpsa (TLSv1.2:AES256-GCM-SHA384:256) (Exim 4.80) (envelope-from ) id 1ij04T-0007sI-T2; Sun, 22 Dec 2019 13:10:54 +0100 Date: Sun, 22 Dec 2019 12:10:52 +0000 Message-ID: <865zi8imr7.wl-maz@kernel.org> From: Marc Zyngier To: Andrew Murray Cc: Marc Zyngier , Catalin Marinas , Will Deacon , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Sudeep Holla , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v2 15/18] perf: arm_spe: Handle guest/host exclusion flags In-Reply-To: <20191220143025.33853-16-andrew.murray@arm.com> References: <20191220143025.33853-1-andrew.murray@arm.com> <20191220143025.33853-16-andrew.murray@arm.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 EasyPG/1.0.0 Emacs/26 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 62.31.163.78 X-SA-Exim-Rcpt-To: andrew.murray@arm.com, marc.zyngier@arm.com, catalin.marinas@arm.com, will.deacon@arm.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, sudeep.holla@arm.com, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on cheepnis.misterjones.org); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 20 Dec 2019 14:30:22 +0000, Andrew Murray wrote: > > A side effect of supporting the SPE in guests is that we prevent the > host from collecting data whilst inside a guest thus creating a black-out > window. This occurs because instead of emulating the SPE, we share it > with our guests. > > Let's accurately describe our capabilities by using the perf exclude > flags to prevent !exclude_guest and exclude_host flags from being used. > > Signed-off-by: Andrew Murray > --- > drivers/perf/arm_spe_pmu.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/perf/arm_spe_pmu.c b/drivers/perf/arm_spe_pmu.c > index 2d24af4cfcab..3703dbf459de 100644 > --- a/drivers/perf/arm_spe_pmu.c > +++ b/drivers/perf/arm_spe_pmu.c > @@ -679,6 +679,9 @@ static int arm_spe_pmu_event_init(struct perf_event *event) > if (attr->exclude_idle) > return -EOPNOTSUPP; > > + if (!attr->exclude_guest || attr->exclude_host) > + return -EOPNOTSUPP; > + I have the opposite approach. If the host decides to profile the guest, why should that be denied? If there is a black hole, it should take place in the guest. Today, the host does expect this to work, and there is no way that we unconditionally allow it to regress. M. -- Jazz is not dead, it just smells funny.