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 8BC83C56201 for ; Thu, 19 Nov 2020 16:40:48 +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 02AA62220B for ; Thu, 19 Nov 2020 16:40:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="MPldfOJy"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="OoOlcSvl" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 02AA62220B 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=KyhIkHB7T0/OVdKG74Kij2lLn/4TvkNIa8MEnVx1Vtk=; b=MPldfOJy7xGVdv+EGYt2uaNqw PTl1rCWfUImSFaX6+M2yOLZp99a1n3NnUdLoLkVPUYW5lxSpA9JAfL2DcBLF/FcDyQPcOkqGSkJII 04ahyUp3n5VAXKtoOhdF1fUO/GcrxalTTe4DhktfRLS5Au/4sjb4NvTkBlanFeERA0uvaC27iukS0 Ck5kHuZz2ieiBBz3Y4bqUvLMXUfXJCs3CTuxk2G7vGdPv5Sol3zoi40+yHFN80oNb6/js/VJWkGOq uCNT8iLSNztKSmJgn9TuyZrs68oMT4dnZ434ryAOF+VDfzzSd0IFOq4DcHV3n4Lw9AZP4ZXlvXtc2 cXwf9eg5Q==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kfmyB-0007hC-3w; Thu, 19 Nov 2020 16:39:39 +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 1kfmy8-0007gQ-3E for linux-arm-kernel@lists.infradead.org; Thu, 19 Nov 2020 16:39:37 +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 F288D2220B; Thu, 19 Nov 2020 16:39:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1605803975; bh=M+kNcVmgZDYx9/XBbh47SkB+8hU/YO4GMxDOKxbKuBI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=OoOlcSvldEoYJaIMOCSULQUSD80i3+NbGdDZG2nY6iHp5pNC4I9LUAnGAinnxtl4f 7f1V3LDx2osEyhUeP0Kkx3gz6/BltwwCqzJobo7nf+By2d5n+ub9kuVHo8kxcijdOc V/1ovyniJzscos2uhY0+wCVoZHZ6tl5kMFaVX5n4= Date: Thu, 19 Nov 2020 16:39:28 +0000 From: Will Deacon To: Peter Zijlstra Subject: Re: [PATCH v3 00/14] An alternative series for asymmetric AArch32 systems Message-ID: <20201119163928.GC4582@willie-the-truck> References: <20201113093720.21106-1-will@kernel.org> <20201119161127.GQ3121392@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201119161127.GQ3121392@hirez.programming.kicks-ass.net> 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_113936_599949_D32D7329 X-CRM114-Status: GOOD ( 21.76 ) 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 , 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 On Thu, Nov 19, 2020 at 05:11:27PM +0100, Peter Zijlstra wrote: > On Fri, Nov 13, 2020 at 09:37:05AM +0000, Will Deacon wrote: > > > The aim of this series is to allow 32-bit ARM applications to run on > > arm64 SoCs where not all of the CPUs support the 32-bit instruction set. > > > > There are some major changes in v3: > > > > * Add some scheduler hooks for restricting a task's affinity mask > > * Implement these hooks for arm64 so that we can avoid 32-bit tasks > > running on 64-bit-only cores > > * Restrict affinity mask of 32-bit tasks on execve() > > * Prevent hot-unplug of all 32-bit CPUs if we have a mismatched system > > * Ensure 32-bit EL0 cpumask is zero-initialised (oops) > > > > It's worth mentioning that this approach goes directly against my > > initial proposal for punting the affinity management to userspace, > > because it turns out that doesn't really work. There are cases where the > > kernel has to muck with the affinity mask explicitly, such as execve(), > > CPU hotplug and cpuset balancing. Ensuring that these don't lead to > > random SIGKILLs as far as userspace is concerned means avoiding any > > Mooo, I thought we were okay with that... Use does stupid, user gets > SIGKIL. What changed? See my other reply, but there are 64-bit apps that execve() a 32-bit payload. I was hoping this could be handling in the C library, but that has no idea about what it's exec'ing beyond the path. Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel