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Tue, 20 Apr 2021 13:26:57 +0000 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 363D3610A1; Tue, 20 Apr 2021 13:26:56 +0000 (UTC) Received: from 78.163-31-62.static.virginmediabusiness.co.uk ([62.31.163.78] helo=why.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94) (envelope-from ) id 1lYqOy-008UxS-VS; Tue, 20 Apr 2021 14:26:53 +0100 Date: Tue, 20 Apr 2021 14:26:52 +0100 Message-ID: <878s5dqe77.wl-maz@kernel.org> From: Marc Zyngier To: Yoan Picchi Cc: james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, catalin.marinas@arm.com, will@kernel.org Subject: Re: [PATCH v2 3/3] KVM: arm64: Add irq_exit counter for kvm_stat In-Reply-To: <20210420130825.15585-4-yoan.picchi@arm.com> References: <20210420130825.15585-1-yoan.picchi@arm.com> <20210420130825.15585-4-yoan.picchi@arm.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") X-SA-Exim-Connect-IP: 62.31.163.78 X-SA-Exim-Rcpt-To: yoan.picchi@arm.com, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, catalin.marinas@arm.com, will@kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210420_062656_686096_D17BF04A X-CRM114-Status: GOOD ( 18.59 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, 20 Apr 2021 14:08:25 +0100, Yoan Picchi wrote: > > This counter is meant to detect when the guest vm exits due to an > interrupt. Those interrupts might be unrelated to the guest VM (say, some > network packet arrived, and such) but they still trigger an exit which is > recorded by the "exit" counter. The main purpose of this counter is to > give some more granularity to this base exit counter so that one can have > a rough idea of where those exits comes from and so, if those general > exits happen because of the host or of the guest. I don't think this makes much sense. Why should we account interrupts for the guest when the interrupts don't have anything to do with it? And guess what, they almost *never* do. The only interrupt that could be accountable to the vcpu is the vPE doorbell, and that one can never causes an exit, by definition. The kernel already provides quite a lot around interrupt accounting already, and I don't think we need to do add more for the guest. If this made any sense, it should be applicable to any userspace task, not just vcpus. Thanks, M. -- Without deviation from the norm, progress is not possible. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel