From patchwork Fri Jul 30 11:24:39 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Will Deacon X-Patchwork-Id: 12411081 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=-17.7 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 B48F1C4338F for ; Fri, 30 Jul 2021 11:33:04 +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 7C8DC60EFE for ; Fri, 30 Jul 2021 11:33:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 7C8DC60EFE Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=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=RJ0ckGBV0Yr/08hYP/0Yj8eSrZp9V+i2FOA3R4ZlRIY=; b=LqMAj/N6Rl4P+S cJ55VbeXrlLpHE4zwwLkKu3EhSdx3oqZM7AEtHJKwQVhRan1fpK2NkiP1tC+wKbL/e5539P9rg4JX NQW++uhw1dZF27FQ4lCVoDcwaJtPi9vPpWul4hXY2fodAOXxpekB69jgHl+z40PeBWbmtsS2hE211 GOgmM6Prk/83Z33KuH5o0wKYTkgBticDn2uej3k3lbxPJUhN/KYSv6gJNmUJblxNZiN3/cMgRB2qd oGmNtPOhAyLSJptYxCJ7hYtHF2QHxchgpk2BXkwIKq5Q84ureK/mGE4gInTFbsbomyk2n//cvSIBx J/lFJSE/nIOgzHy/hv7g==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1m9Qid-008JgA-Gi; Fri, 30 Jul 2021 11:30:24 +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 1m9Qe4-008HYX-2v for linux-arm-kernel@lists.infradead.org; Fri, 30 Jul 2021 11:25:41 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id 3D9B76101C; Fri, 30 Jul 2021 11:25:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1627644339; bh=YiNgY8+kTBdYeqURjU5xY5wvK1Ur/VHfTq38waThEcQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=B67CT5aFUcNhTgH3L8ctFQCwWykZZrvqOvBKcnUHgW/h50xBHxQhK4vIJaB3af6be C0fNTSFujlB5bT/U1j0qfXspeVQXejynDJKo84pFuJT7PZUYfpPIEtlPSzfV/k/6Jn J6H3MqxVthdE+HbgR+YLJKivoV1u9e6SRlfxRdqZfd30QD56lh3xP/is2iHEQHkYFe CDYjmoceAL5DkNqft0GS0VIw0LwL+Acf6BCz/GPGohEh3HJtxKcUqaAcAovRIZeJtt si06Z8RzXWazWG6MVHidhsOrEyuyQsUtcVDIb75Tn+KjRMtmjrrv7nUgML+DTJBBNm pWl+cdQvLiOMA== 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 , Valentin Schneider , Mark Rutland , kernel-team@android.com Subject: [PATCH v11 12/16] arm64: Prevent offlining first CPU with 32-bit EL0 on mismatched system Date: Fri, 30 Jul 2021 12:24:39 +0100 Message-Id: <20210730112443.23245-13-will@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20210730112443.23245-1-will@kernel.org> References: <20210730112443.23245-1-will@kernel.org> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210730_042540_223498_0DD18A39 X-CRM114-Status: GOOD ( 16.99 ) 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 | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index 125d5c9471ac..d99a29f52aa1 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -2900,15 +2900,38 @@ void __init setup_cpu_features(void) static int enable_mismatched_32bit_el0(unsigned int cpu) { + /* + * The first 32-bit-capable CPU we detected and so can no longer + * be offlined by userspace. -1 indicates we haven't yet onlined + * a 32-bit-capable 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; }