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=-5.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,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 26425C388F9 for ; Wed, 21 Oct 2020 15:11:51 +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 7773C20BED for ; Wed, 21 Oct 2020 15:11:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="Xe70yJuD" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7773C20BED Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com 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=pE5Y0C0jgyY+hHmNDebkGz5QAeMrNiXkYAUHPBTJ6nI=; b=Xe70yJuDo7tQlOhoqPAsw2eR3 Cc91IYzO20QzgJEu2OWCQS9VcLG9o1oqG5pCcTYDpDaGMmZjMxQODhR9yKG0fBEGRklS9t9w8TLXo 5LDsCP6sUdIy3z1hUaQT9G/b0SJFVSH7enUyE/VBKvCAkdd4EfOQKLnvLqZzMH+aKdjHG6ULTkI6w zuBqLNy4zZN3iqfIlgv+jjC8ON3pZlq56yNT1dmEwCbA9fJvSzV2NvXdm6gYAdrXC8p/szsJRdXoC ZKUthxTfntRUCPLY0JPAhIHAK7psDZFvbBLjzC/jdmL8psbylsIMB4DDI2c3Rd7yVx3EAfTiH8fK0 4tBUnfnyA==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kVFkl-0003hA-8G; Wed, 21 Oct 2020 15:10:15 +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 1kVFkh-0003fy-Lv for linux-arm-kernel@lists.infradead.org; Wed, 21 Oct 2020 15:10:12 +0000 Received: from gaia (unknown [95.145.162.19]) (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 97A3B20BED; Wed, 21 Oct 2020 15:10:08 +0000 (UTC) Date: Wed, 21 Oct 2020 16:10:06 +0100 From: Catalin Marinas To: Will Deacon Subject: Re: [RFC PATCH v2 4/4] arm64: Export id_aar64fpr0 via sysfs Message-ID: <20201021151005.GF3976@gaia> References: <20201021104611.2744565-1-qais.yousef@arm.com> <20201021104611.2744565-5-qais.yousef@arm.com> <63fead90e91e08a1b173792b06995765@kernel.org> <20201021121559.GB3976@gaia> <20201021133316.GF8004@e123083-lin> <20201021140945.GD3976@gaia> <20201021144542.GB17912@willie-the-truck> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201021144542.GB17912@willie-the-truck> 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-20201021_111011_842459_B28129B0 X-CRM114-Status: GOOD ( 26.38 ) 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, "Peter Zijlstra \(Intel\)" , Marc Zyngier , Qais Yousef , James Morse , Greg Kroah-Hartman , Linus Torvalds , 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 On Wed, Oct 21, 2020 at 03:45:43PM +0100, Will Deacon wrote: > On Wed, Oct 21, 2020 at 03:09:46PM +0100, Catalin Marinas wrote: > > Anyway, if the task placement is entirely off the table, the next thing > > is asking applications to set their own mask and kill them if they do > > the wrong thing. Here I see two possibilities for killing an app: > > > > 1. When it ends up scheduled on a non-AArch32-capable CPU > > That sounds fine to me. If we could do the exception return and take a > SIGILL, that's what we'd do, but we can't so we have to catch it before. Indeed, the illegal ERET doesn't work for this scenario. > > 2. If the user cpumask (bar the offline CPUs) is not a subset of the > > aarch32_mask > > > > Option 1 is simpler but 2 would be slightly more consistent. > > I disagree -- if we did this for something like fpsimd, then the consistent > behaviour would be to SIGILL on the cores without the instructions. For fpsimd it makes sense since the main ISA is still available and the application may be able to do something with the signal. But here we can't do much since the entire AArch32 mode is not supported. That's why we went for SIGKILL instead of SIGILL but thinking of it, after execve() the signals are reset to SIG_DFL so SIGILL cannot be ignored. I think it depends on whether you look at this fault as a part of ISA not being available or as the overall application not compatible with the system it is running on. If the latter, option 2 above makes more sense. > > There's also the question on whether the kernel should allow an ELF32 to > > be loaded (and potentially killed subsequently) if the user mask is not > > correct on execve(). > > I don't see the point in distinguishing between "you did execve() on a core > without 32-bit" and "you did execve() on a core with 32-bit and then > migrated to a core without 32-bit". In the context of option 2 above, its more about whether execve() returns -ENOEXEC or the process gets a SIGKILL immediately. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel