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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 32C68C4361B for ; Thu, 17 Dec 2020 10:56:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CE0102389B for ; Thu, 17 Dec 2020 10:56:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726601AbgLQK4d (ORCPT ); Thu, 17 Dec 2020 05:56:33 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59780 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726155AbgLQK4c (ORCPT ); Thu, 17 Dec 2020 05:56:32 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 23BCBC061794; Thu, 17 Dec 2020 02:55:52 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=Ycg1OWAhAt+ZzpKUE25E7HoWCVHWxaXFmMVVBcTRYoc=; b=NX0krpKMDNxEPEbp50YVfpAz4B hyMdM2+iQL70Wd2u931sbt7vRbCXKNXaBjRhXJptWC11dhxVFLsaBcKUDNVWwn5DtkuUar0yPhU3b 8xLaBCsCa5Agp8bQGosbLmujhoHo+gATn89UWeH1Ok+FZiMFDCFI/VKJJlnxFiGUdhRu/lAjI8ESE MdaoVigvRXpekClccOpK2+UWLGEjnjvCamelEi6uRV3r9VeL85PlTrXJiDz760jRD64NnT2mK6GQw t+80Xn9VhHbYMiTq3g/WumfWH+8VD+dyHACE8qhA+xB1DDsIm5fR23eG/WIOmQ52WiIe0PuYlbxSG THr/Gwow==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kpqwZ-0004TP-58; Thu, 17 Dec 2020 10:55:35 +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 9246D305C11; Thu, 17 Dec 2020 11:55:33 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 67014202395BD; Thu, 17 Dec 2020 11:55:33 +0100 (CET) Date: Thu, 17 Dec 2020 11:55:33 +0100 From: Peter Zijlstra To: Will Deacon Cc: linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, Catalin Marinas , Marc Zyngier , Greg Kroah-Hartman , Morten Rasmussen , Qais Yousef , Suren Baghdasaryan , Quentin Perret , Tejun Heo , Li Zefan , Johannes Weiner , Ingo Molnar , Juri Lelli , Vincent Guittot , kernel-team@android.com Subject: Re: [PATCH v5 00/15] An alternative series for asymmetric AArch32 systems Message-ID: <20201217105533.GV3040@hirez.programming.kicks-ass.net> References: <20201208132835.6151-1-will@kernel.org> <20201215173645.GJ3040@hirez.programming.kicks-ass.net> <20201215185012.GA15566@willie-the-truck> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201215185012.GA15566@willie-the-truck> Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On Tue, Dec 15, 2020 at 06:50:12PM +0000, Will Deacon wrote: > On Tue, Dec 15, 2020 at 06:36:45PM +0100, Peter Zijlstra wrote: > > IOW, any (accidental or otherwise) trip through a 32bit helper, will > > destroy user state (the affinity mask: 0x3c). > > Yes, that's correct, and I agree that it's a rough edge. If you're happy > with the idea of adding an extra mask to make this work, then I can start > hacking that up Yeah, I'm afraid we'll have to, this asymmetric muck is only going to get worse from here on. Anyway, I think we can avoid adding another cpumask_t to task_struct and do with a cpumask_t * insteads. After all, for 'normal' tasks, the task_cpu_possible_mask() will be cpu_possible_mask and we don't need to carry anything extra. Only once we hit one of these assymetric ISA things, can the task allocate the additional cpumask and retain the full mask. > (although I doubt I'll get something out before the new > year at this point). Yeah, we're all about to shut down for a bit, I'll not be looking at email for 2 weeks either, so even if you send it, I might not see it until the next year.