From patchwork Tue Jun 8 18:03:09 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Will Deacon X-Patchwork-Id: 12307887 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=-17.2 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 AAB2BC47082 for ; Tue, 8 Jun 2021 18:19:53 +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 742D66136D for ; Tue, 8 Jun 2021 18:19:53 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 742D66136D 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=PbFX2nymPkIXwgcnsWSq9Zbg+A2Nb6FmtMOGQ36gE4M=; b=sET4HGopwu6J+6 GOejTqblkARs/bctyRlRZX/jqYQWT9HceDFUkMmj8apeob3GUFs4fJwfo36PTQt/MLlQEHbvglBYU eg0n5cLlSKKAy9fTrkD5RAodg9rQfpm88mebj0ZtRQdXBQEUggRkMr93A9gwXd6DJk1mC0JsfgIT7 k9kGpOSudhxjaIzNRtbEsRbrG2HbNHq2fZahZuOKLw8doIFGO/+AzoPm9ft6moE9/UXTgFPJ8m1+7 xym+11tK2H1IyfyUuUFqtcUO+t4kzCYYifaSChCJmgcUk19H4daMIFEY6PAvCEgePC40R8Fr3/+WM Un7DD8AvDFYcoluzfHZg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1lqgIG-009wYi-OO; Tue, 08 Jun 2021 18:17:42 +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 1lqg5Y-009rAU-P1 for linux-arm-kernel@lists.infradead.org; Tue, 08 Jun 2021 18:04:34 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id DAF6E61377; Tue, 8 Jun 2021 18:04:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1623175472; bh=DOju4Qkdazocj9FpNAdyJz+fzAXLHJIskweDvyX2/bU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=OfjBOue9fuzmxPOj/KqDgcNGa3da8OVKKo7EO0duS+WlkqRCrDKbdCxVqPahZvvTb M+JMkvAxtYMsqFvMBljOy5Y9xumEguWoqKouE8auloXnklab3qZ6jqRmZPDsaBxihp IFzw4Dl9QmPzsoM4hz1yODCeXAEWzyXu8mYmMljzl+KH+rk8pN3t7xMZc1UXxdOAm1 ERjxp0gq4jmc6HCW3eSVAPYQRJcJFqmyf3I9FVdTVzmRUk2p9wiWbb736+haSzjhot Lfo24qGPoj+k9iXVdUzo5b2XRSFeGe1itBj+2JWHI9jaYWF6TdjG18GzkR1y80Nih+ dWtl0GHyM6nxw== 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 v9 16/20] arm64: Prevent offlining first CPU with 32-bit EL0 on mismatched system Date: Tue, 8 Jun 2021 19:03:09 +0100 Message-Id: <20210608180313.11502-17-will@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20210608180313.11502-1-will@kernel.org> References: <20210608180313.11502-1-will@kernel.org> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210608_110432_862574_3A872E63 X-CRM114-Status: GOOD ( 16.65 ) 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 d735dd13167b..55a58933e3b2 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -2877,15 +2877,38 @@ 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; }