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=-5.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 C4ED3C2D0E4 for ; Thu, 19 Nov 2020 13:14:14 +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 34F88208D5 for ; Thu, 19 Nov 2020 13:14:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="hoJvtxxG"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="vwnHgZxH" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 34F88208D5 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=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: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=V68VJz1bPs9me0UFxr4mjmaHAeWevAhAYtW3Sn8RcYM=; b=hoJvtxxGv0JZ+tjkzsv3h5tM9 VVMc8d/pdBNILR7dSS+/UHx3uR2GKpfM1FauzzQwk7zocOA+D5AJRpyYhe53U2t9BbqLsOXAVmuvP D90TahduN06nqXhXN1rB0NHimGf42j1+i7+FqKvNdiSpe5XqWVHWUkP0x6ijGptJHtA5y2zbWt2RM WGUm/xk74QnWGNXjMpr1tTr8KGQIwZLJvYmCqJg+jXkHbQDaDQISx5dGvdQMKVhvb08RDS2ydQVFM W1U5oiPYhWxksp24pah+zhNlOfbTizn3hNBScaq2pn702K9gPLxB3n1gTg7t2nxfsgJHY0xxlKKJs 5ZCk7QCxQ==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kfjk7-00052w-22; Thu, 19 Nov 2020 13:12:55 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kfjjx-00050u-JN for linux-arm-kernel@lists.infradead.org; Thu, 19 Nov 2020 13:12:46 +0000 Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (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 41CC52222A; Thu, 19 Nov 2020 13:12:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1605791564; bh=+S1H0ZJpI+XEJQFoYwrcrygpnJ+0WlSbLdnlvQ3oIAY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=vwnHgZxHP8mA72dLl+N1D1ijUGgvL48bEfydoyKdJw0kCsH7hurie2mO1R1i2q/xR d+ZGYDXjrWiC1kZq5o38c0ehtfEQvVEVLzAPy2RjlUQGkFivVKHEldZ0c0wEf+N8UZ TEOeuRZVLsRMX2oRy5EFkwQ7cihGGQsv9enII3NM= Date: Thu, 19 Nov 2020 13:12:37 +0000 From: Will Deacon To: Valentin Schneider Subject: Re: [PATCH v3 02/14] arm64: Allow mismatched 32-bit EL0 support Message-ID: <20201119131236.GC4331@willie-the-truck> References: <20201113093720.21106-1-will@kernel.org> <20201113093720.21106-3-will@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201119_081245_961537_04311946 X-CRM114-Status: GOOD ( 16.49 ) 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: linux-arch@vger.kernel.org, Marc Zyngier , kernel-team@android.com, Vincent Guittot , Juri Lelli , Quentin Perret , Peter Zijlstra , Catalin Marinas , Johannes Weiner , linux-kernel@vger.kernel.org, Qais Yousef , Ingo Molnar , Li Zefan , Greg Kroah-Hartman , Tejun Heo , Suren Baghdasaryan , Morten Rasmussen , linux-arm-kernel@lists.infradead.org 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 Hi Valentin, Thanks for the review. On Thu, Nov 19, 2020 at 11:27:41AM +0000, Valentin Schneider wrote: > > On 13/11/20 09:37, Will Deacon wrote: > > +const struct cpumask *system_32bit_el0_cpumask(void) > > +{ > > + if (!system_supports_32bit_el0()) > > + return cpu_none_mask; > > + > > + if (static_branch_unlikely(&arm64_mismatched_32bit_el0)) > > + return cpu_32bit_el0_mask; > > + > > + return cpu_present_mask; > > +} > > Nit: this is used in patch 13 to implement arch_cpu_allowed_mask(). Since > that latter defaults to cpu_possible_mask, this probably should too. My original thinking was that, in a system where 32-bit EL0 support is detected at boot and we're not handling mismatches, then it would be nice to avoid saying that late CPUs are all 32-bit capable given that they will fail to be onlined if they're not. However, the reality is that we don't currently distinguish between the present and possible masks on arm64 so it doesn't make any difference. It's also not useful to userspace, because if the cores aren't online then so what? Your observation above is another nail in the coffin, so I'll change this to the possible mask as you suggest. Cheers, Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel