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=-17.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 DFC72C56201 for ; Thu, 19 Nov 2020 16:51:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7AA4E238E6 for ; Thu, 19 Nov 2020 16:51:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="LkHwoaUy" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729061AbgKSQv7 (ORCPT ); Thu, 19 Nov 2020 11:51:59 -0500 Received: from mail.kernel.org ([198.145.29.99]:59588 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728556AbgKSQv6 (ORCPT ); Thu, 19 Nov 2020 11:51:58 -0500 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 67BA72222A; Thu, 19 Nov 2020 16:51:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1605804717; bh=RFyifzzbOlzqjeSQXuFb5hOWTQ4MmRBvgLj1aJ/TrPI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=LkHwoaUyQJoZSh39n3MIBLsq4d/YOYWRlbb6Ogc1OoA51WDUt3KBEKAqUzg7L9hrm qGw4S62Ow75kCfFDheE9yS3l56jAtcN8Q21vRNTm9Ie54xgWal4ZxTXE/dSl7JiQB/ rgMDfrVdB/cAtU32bAK9+gUrlRu8At+0EOQAr9BY= Date: Thu, 19 Nov 2020 16:51:51 +0000 From: Will Deacon To: Peter Zijlstra Cc: Quentin Perret , 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 , Tejun Heo , Li Zefan , Johannes Weiner , Ingo Molnar , Juri Lelli , Vincent Guittot , kernel-team@android.com Subject: Re: [PATCH v3 08/14] arm64: exec: Adjust affinity for compat tasks with mismatched 32-bit EL0 Message-ID: <20201119165150.GA4665@willie-the-truck> References: <20201113093720.21106-1-will@kernel.org> <20201113093720.21106-9-will@kernel.org> <20201119092407.GB2416649@google.com> <20201119110603.GB3946@willie-the-truck> <20201119161956.GS3121392@hirez.programming.kicks-ass.net> <20201119163035.GB4582@willie-the-truck> <20201119164411.GV3121392@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201119164411.GV3121392@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On Thu, Nov 19, 2020 at 05:44:11PM +0100, Peter Zijlstra wrote: > On Thu, Nov 19, 2020 at 04:30:36PM +0000, Will Deacon wrote: > > On Thu, Nov 19, 2020 at 05:19:56PM +0100, Peter Zijlstra wrote: > > > On Thu, Nov 19, 2020 at 11:06:04AM +0000, Will Deacon wrote: > > > > On Thu, Nov 19, 2020 at 09:24:07AM +0000, Quentin Perret wrote: > > > > > On Friday 13 Nov 2020 at 09:37:13 (+0000), Will Deacon wrote: > > > > > > When exec'ing a 32-bit task on a system with mismatched support for > > > > > > 32-bit EL0, try to ensure that it starts life on a CPU that can actually > > > > > > run it. > > > > > > > > > > > > Signed-off-by: Will Deacon > > > > > > --- > > > > > > arch/arm64/kernel/process.c | 12 +++++++++++- > > > > > > 1 file changed, 11 insertions(+), 1 deletion(-) > > > > > > > > > > > > diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c > > > > > > index 1540ab0fbf23..17b94007fed4 100644 > > > > > > --- a/arch/arm64/kernel/process.c > > > > > > +++ b/arch/arm64/kernel/process.c > > > > > > @@ -625,6 +625,16 @@ unsigned long arch_align_stack(unsigned long sp) > > > > > > return sp & ~0xf; > > > > > > } > > > > > > > > > > > > +static void adjust_compat_task_affinity(struct task_struct *p) > > > > > > +{ > > > > > > + const struct cpumask *mask = system_32bit_el0_cpumask(); > > > > > > + > > > > > > + if (restrict_cpus_allowed_ptr(p, mask)) > > > > > > + set_cpus_allowed_ptr(p, mask); > > > > > > > > > > My understanding of this call to set_cpus_allowed_ptr() is that you're > > > > > mimicking the hotplug vs affinity case behaviour in some ways. That is, > > > > > if a task is pinned to a CPU and userspace hotplugs that CPU, then the > > > > > kernel will reset the affinity of the task to the remaining online CPUs. > > > > > > > > Correct. It looks to the 32-bit application like all the 64-bit-only CPUs > > > > were hotplugged off at the point of the execve(). > > > > > > This doesn't respect cpusets though :/ > > > > How does that differ from select_fallback_rq()? > > That has that cpuset state it tries first, only if that fails does it do > the possible mask. Fair enough. Lemme try something similar here before overriding the mask entirely... Will