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=-3.8 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 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 70A10C56201 for ; Thu, 19 Nov 2020 16:12:42 +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 E964422256 for ; Thu, 19 Nov 2020 16:12:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="UF2Va3XG" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E964422256 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.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=3+Zbs621/YD2Zg1RbVjccobwkPyGkreSoJu5jdR8yMc=; b=UF2Va3XGHpDXTrkSzfxiALhDa B9ol5sCrUpRrYltx2puFZ7ahMJzyuCglphaLvvUhWLFAkJ+J8gTAZbgkam8fXIpGbAMs0L0WhkSjo MXXz7TjXH6KHvHhGEhGRGnqmbCR4DWAxD0F1I4Ktdyba+xV0jV40moJzHWKAKAtFE+nQPqs+SPD6z 23wGrjEWQ8D+T9K1yUnP0TsqOI+p7bo//hjH8EWTqjgptR39rdUayjZzLQrefApGGzGqsfK/M27n2 G4cxHG/gSchPdd38Z6BgUftYYh3OEJ8m83oM0rlkeSmYigOvaMTxSrKZ0wX8s0pYjM/cLC3YU3LEq RSt46uoYg==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kfmWy-0001Ym-Gc; Thu, 19 Nov 2020 16:11:32 +0000 Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kfmWw-0001Xy-06; Thu, 19 Nov 2020 16:11:30 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 346B33011C6; Thu, 19 Nov 2020 17:11:27 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 20385203C45DF; Thu, 19 Nov 2020 17:11:27 +0100 (CET) Date: Thu, 19 Nov 2020 17:11:27 +0100 From: Peter Zijlstra To: Will Deacon Subject: Re: [PATCH v3 00/14] An alternative series for asymmetric AArch32 systems Message-ID: <20201119161127.GQ3121392@hirez.programming.kicks-ass.net> References: <20201113093720.21106-1-will@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201113093720.21106-1-will@kernel.org> 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 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? > 64-bit-only CPUs appearing in the affinity mask for a 32-bit task, at > which point it's easier just to handle everything in the kernel anyway. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel