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=-11.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS autolearn=ham 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 E5D17C63697 for ; Thu, 26 Nov 2020 15:34:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8E03E21D46 for ; Thu, 26 Nov 2020 15:34:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="nIqV3mB4" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391408AbgKZPeT (ORCPT ); Thu, 26 Nov 2020 10:34:19 -0500 Received: from mail.kernel.org ([198.145.29.99]:49458 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730987AbgKZPeR (ORCPT ); Thu, 26 Nov 2020 10:34:17 -0500 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 0729821D46; Thu, 26 Nov 2020 15:34:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1606404857; bh=Igx9jXBr7rpPOrw2MqxIsTEP9nndo9myMGoaHB2g/iU=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=nIqV3mB40duYn7B9JjVKyQhYGKWwujORRiFiiVPiXLxlIOSwKwVa0X9U9n6FOVCxT DxkADEC1BnDQ6kWO4ArX0X+EjeN4eSH2VJJUIlGiuydBv1nTNbUW6eerpsJVp+bF7j hTaLSTLt1uiueA5OJ0v/jqA+fYaZIT3C/smkDufQ= Received: from disco-boy.misterjones.org ([51.254.78.96] helo=www.loen.fr) by disco-boy.misterjones.org with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.94) (envelope-from ) id 1kiJHi-00DqFH-DH; Thu, 26 Nov 2020 15:34:14 +0000 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Date: Thu, 26 Nov 2020 15:34:14 +0000 From: Marc Zyngier To: Alexandru Elisei Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH 6/8] KVM: arm64: Remove dead PMU sysreg decoding code In-Reply-To: <1ed6dfd6-4ace-a562-bc2f-054a5c853fa6@arm.com> References: <20201113182602.471776-1-maz@kernel.org> <20201113182602.471776-7-maz@kernel.org> <1ed6dfd6-4ace-a562-bc2f-054a5c853fa6@arm.com> User-Agent: Roundcube Webmail/1.4.9 Message-ID: <3ae09ecc95b732129f71076b4b59c873@kernel.org> X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: alexandru.elisei@arm.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, kernel-team@android.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Hi Alex, On 2020-11-26 15:18, Alexandru Elisei wrote: > Hi Marc, > > I checked and indeed the remaining cases cover all registers that use > this accessor. > > However, I'm a bit torn here. The warning that I got when trying to run > a guest > with the PMU feature flag set, but not initialized (reported at [1]) > was also not > supposed to ever be reached: > > static u32 kvm_pmu_event_mask(struct kvm *kvm) > { >     switch (kvm->arch.pmuver) { >     case 1:            /* ARMv8.0 */ >         return GENMASK(9, 0); >     case 4:            /* ARMv8.1 */ >     case 5:            /* ARMv8.4 */ >     case 6:            /* ARMv8.5 */ >         return GENMASK(15, 0); >     default:        /* Shouldn't be here, just for sanity */ >         WARN_ONCE(1, "Unknown PMU version %d\n", kvm->arch.pmuver); >         return 0; >     } > } > > I realize it's not exactly the same thing and I'll leave it up to you > if you want > to add a warning for the cases that should never happen. I'm fine > either way: I already have queued such a warning[1]. It turns out that LLVM warns idx can be left uninitialized, and shouts. Let me know if that works for you. Thanks, M. [1] https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/commit/?h=kvm-arm64/pmu-undef&id=af7eff70eaf8f28179334f5aeabb70a306242c83 -- Jazz is not dead. It just smells funny...