From patchwork Tue May 25 15:14:29 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Will Deacon X-Patchwork-Id: 12279307 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=-17.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 13E8BC2B9F8 for ; Tue, 25 May 2021 15:36:23 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 D3BC860FDA for ; Tue, 25 May 2021 15:36:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D3BC860FDA Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org 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=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=7i/1PtY6vI1lSlQXJo7EMjTZQMoDSwtPMsTf6KZjs3Q=; b=DzuSNi4L6svn5e wqV/xo5mPtb3FJpuHpansfLHe2fDdCwZdAfPBMwGObpxqxTnZq97psNsB3QxlPDht3LSENY3HrnjU t4BXOd5zVrfgQXEctCsN1u2SDE1QmnKg3hoV1fxQ9bSer43MeU51scXc1vUTm/SZ9vw5C9Yhl+Vzo 57N0DXqvOMkx1essBNE4FWU+nYVPxGH0o1PvAiRKs/5fX9GeNe7dZ1jMfMiBVZrJStXZ/jjx5rgzQ SydsdepGQch0y16mLJExEO34dF5CC0zIGJH5TOL+I6vm27k0ldqvyd5CE/Q4iwNEDowy1SydVufIr QH5g1VKM8Id9nhnCfhUA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1llZ4T-0062LP-7m; Tue, 25 May 2021 15:34:18 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1llYnD-005u3q-Ar for linux-arm-kernel@lists.infradead.org; Tue, 25 May 2021 15:16:28 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id AEB816141C; Tue, 25 May 2021 15:16:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1621955787; bh=nSPy9SuPb1FO/mDztTPLt4/d9CdHbLFYERw4tXoz0Kw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BJ+pNO4rqX8DQBMEkPtuN0vy2sWPDrc/M+7cHmrCj4P4mgUDhRtJDPrtQgdXQ/Nqu ZFD/JFAFCDoH2CkInfTtjAREMB+wvekyyDjT6grP2FTu5u8eoMq8dxdlxSovV3WnXS m5zbN/RqIE0lTwos1bBeKb/k6kwZqMawypoFd1QT9/N74SEYZtKBSyGYisyP3qE82N m9gCDuNZK1rFJemOea+/Zzm39lM7j9Gbi1xdp4I7EV0ESxz7rBDZPNaqG5cvdXNRMT W1rM61F7T2R7Rk3MoA75ZH7MK+T0EWQyUm1lQs9uj8K/Y+Fi+AMuOI+nmJz+li7Fhr pKsFDcXgooLyQ== From: Will Deacon To: linux-arm-kernel@lists.infradead.org Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, Will Deacon , Catalin Marinas , Marc Zyngier , Greg Kroah-Hartman , Peter Zijlstra , Morten Rasmussen , Qais Yousef , Suren Baghdasaryan , Quentin Perret , Tejun Heo , Johannes Weiner , Ingo Molnar , Juri Lelli , Vincent Guittot , "Rafael J. Wysocki" , Dietmar Eggemann , Daniel Bristot de Oliveira , kernel-team@android.com Subject: [PATCH v7 19/22] arm64: Prevent offlining first CPU with 32-bit EL0 on mismatched system Date: Tue, 25 May 2021 16:14:29 +0100 Message-Id: <20210525151432.16875-20-will@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20210525151432.16875-1-will@kernel.org> References: <20210525151432.16875-1-will@kernel.org> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210525_081627_485905_6119BFBE X-CRM114-Status: GOOD ( 15.41 ) 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: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org If we want to support 32-bit applications, then when we identify a CPU with mismatched 32-bit EL0 support we must ensure that we will always have an active 32-bit CPU available to us from then on. This is important for the scheduler, because is_cpu_allowed() will be constrained to 32-bit CPUs for compat tasks and forced migration due to a hotplug event will hang if no 32-bit CPUs are available. On detecting a mismatch, prevent offlining of either the mismatching CPU if it is 32-bit capable, or find the first active 32-bit capable CPU otherwise. Reviewed-by: Catalin Marinas Signed-off-by: Will Deacon --- arch/arm64/kernel/cpufeature.c | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index 959442f76ed7..72efdc611b14 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -2896,15 +2896,33 @@ void __init setup_cpu_features(void) static int enable_mismatched_32bit_el0(unsigned int cpu) { + static int lucky_winner = -1; + struct cpuinfo_arm64 *info = &per_cpu(cpu_data, cpu); bool cpu_32bit = id_aa64pfr0_32bit_el0(info->reg_id_aa64pfr0); if (cpu_32bit) { cpumask_set_cpu(cpu, cpu_32bit_el0_mask); static_branch_enable_cpuslocked(&arm64_mismatched_32bit_el0); - setup_elf_hwcaps(compat_elf_hwcaps); } + if (cpumask_test_cpu(0, cpu_32bit_el0_mask) == cpu_32bit) + return 0; + + if (lucky_winner >= 0) + return 0; + + /* + * We've detected a mismatch. We need to keep one of our CPUs with + * 32-bit EL0 online so that is_cpu_allowed() doesn't end up rejecting + * every CPU in the system for a 32-bit task. + */ + lucky_winner = cpu_32bit ? cpu : cpumask_any_and(cpu_32bit_el0_mask, + cpu_active_mask); + get_cpu_device(lucky_winner)->offline_disabled = true; + setup_elf_hwcaps(compat_elf_hwcaps); + pr_info("Asymmetric 32-bit EL0 support detected on CPU %u; CPU hot-unplug disabled on CPU %u\n", + cpu, lucky_winner); return 0; }