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=-10.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 autolearn=unavailable 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 430F5C433E0 for ; Thu, 28 Jan 2021 18:44:34 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id D60E764E05 for ; Thu, 28 Jan 2021 18:44:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D60E764E05 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=hUyXDsR9nJLnV/BI8Hii669QyBOJSe+nFza3DPmXuFs=; b=gCmqMpid1MIVkf2PKgHXPY+TL KnhyXODZ02bhT46/TlGQmgvJ+XjKjvKir1+htC6XWBSvM5KZb3bhePphIsFfEOhIiCelM7ErJsvH/ j2r7g+mxS+iNaZtYSuCWIRMZmZlTm6f6NrHXXcaGS1w7S29zc7afC5mrfynsuji/ZF8nx6tEOhAae k/wnQ6bltYiMHsbO8MgwBvhUk3BoeJE69p2NeXQqgqP2vU223fofLs4GJfcGJz95oMDGJYjSs7roy Kvtyccn4EDTw35rGfn3V8Iy0aekkP4o9GKpeGQ+N6mgeeM1SAvXeIYS0wz+qTQaPN5b43mQ1nkrWo RD8TVgacQ==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1l5CGJ-0003AA-1P; Thu, 28 Jan 2021 18:43:23 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1l5CGG-00039i-VF for linux-arm-kernel@lists.infradead.org; Thu, 28 Jan 2021 18:43:21 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id BAA8E13A1; Thu, 28 Jan 2021 10:43:13 -0800 (PST) Received: from slackpad.fritz.box (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A1B4D3F719; Thu, 28 Jan 2021 10:43:12 -0800 (PST) Date: Thu, 28 Jan 2021 18:42:31 +0000 From: Andre Przywara To: Marc Zyngier Subject: Re: [PATCH 1/2] KVM: arm64: Turn kvm_arm_support_pmu_v3() into a static key Message-ID: <20210128184231.711e0c54@slackpad.fritz.box> In-Reply-To: <9bf9be4149cfd0671fe5178ce553159b@kernel.org> References: <20210126151521.2958688-1-maz@kernel.org> <20210126151521.2958688-2-maz@kernel.org> <20210128151643.6e2c3668@slackpad.fritz.box> <9bf9be4149cfd0671fe5178ce553159b@kernel.org> Organization: Arm Ltd. X-Mailer: Claws Mail 3.17.1 (GTK+ 2.24.31; x86_64-slackware-linux-gnu) MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210128_134321_088228_2BDDBA49 X-CRM114-Status: GOOD ( 22.82 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Suzuki K Poulose , James Morse , linux-arm-kernel@lists.infradead.org, kernel-team@android.com, kvmarm@lists.cs.columbia.edu, Julien Thierry 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 Thu, 28 Jan 2021 16:56:01 +0000 Marc Zyngier wrote: > On 2021-01-28 15:16, Andre Przywara wrote: > > On Tue, 26 Jan 2021 15:15:20 +0000 > > Marc Zyngier wrote: > > > > Hi Marc, > > > >> We currently find out about the presence of a HW PMU (or the handling > >> of that PMU by perf, which amounts to the same thing) in a fairly > >> roundabout way, by checking the number of counters available to perf. > >> That's good enough for now, but we will soon need to find about about > >> that on paths where perf is out of reach (in the world switch). > >> > >> Instead, let's turn kvm_arm_support_pmu_v3() into a static key. > > > > I am sure the pesky build bot has told you about it already, but this > > fails when ARM_PMU is not defined, as perf_num_counters() is not > > defined. It's bit nasty, since it's a generic function, so we > > can't easily stub it in its original header. > > No sign from the bot yet, but that's indeed a problem. Well spotted. > > > Shall we find a place somewhere in arch/arm64 and provide a stub > > implementation there, #ifndef CONFIG_ARM_PMU? Sounds ugly, though. > > > > Or something else entirely? > > How about: > > diff --git a/arch/arm64/kvm/perf.c b/arch/arm64/kvm/perf.c > index 198fa4266b2d..739164324afe 100644 > --- a/arch/arm64/kvm/perf.c > +++ b/arch/arm64/kvm/perf.c > @@ -55,7 +55,7 @@ int kvm_perf_init(void) > * hardware performance counters. This could ensure the presence of > * a physical PMU and CONFIG_PERF_EVENT is selected. > */ > - if (perf_num_counters() > 0) > + if (IS_ENABLED(CONFIG_ARM_PMU) && perf_num_counters() > 0) Neat! That indeed compiles and works in both cases (w/ and w/o ARM_PMU), fixing the original BUG I saw when using this as the L1 kernel. Thanks! Andre > static_branch_enable(&kvm_arm_pmu_available); > > return perf_register_guest_info_callbacks(&kvm_guest_cbs); > > It certainly compiles here. > > M. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel