From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=BAYES_00,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 60820C433B4 for ; Tue, 20 Apr 2021 13:27:08 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id 9DADF61003 for ; Tue, 20 Apr 2021 13:27:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9DADF61003 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvmarm-bounces@lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id D045A4B353; Tue, 20 Apr 2021 09:27:06 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 7tcJk335kZw6; Tue, 20 Apr 2021 09:27:02 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 344E24B396; Tue, 20 Apr 2021 09:27:02 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 8176C4B353 for ; Tue, 20 Apr 2021 09:27:01 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id hzBVYF3R+X9W for ; Tue, 20 Apr 2021 09:26:57 -0400 (EDT) Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id 6854A4B324 for ; Tue, 20 Apr 2021 09:26:57 -0400 (EDT) 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 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 Cc: catalin.marinas@arm.com, will@kernel.org, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu 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. _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm