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=-8.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,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 01F79C55179 for ; Thu, 29 Oct 2020 01:01:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AC07D20791 for ; Thu, 29 Oct 2020 01:01:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729954AbgJ2BBM (ORCPT ); Wed, 28 Oct 2020 21:01:12 -0400 Received: from mail.kernel.org ([198.145.29.99]:60518 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731525AbgJ1WR1 (ORCPT ); Wed, 28 Oct 2020 18:17:27 -0400 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 CDD7324694; Wed, 28 Oct 2020 15:14:45 +0000 (UTC) Date: Wed, 28 Oct 2020 15:14:43 +0000 From: Catalin Marinas To: Will Deacon Cc: linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org, Marc Zyngier , Greg Kroah-Hartman , Peter Zijlstra , Morten Rasmussen , Qais Yousef , Suren Baghdasaryan , kernel-team@android.com Subject: Re: [PATCH 5/6] arm64: Advertise CPUs capable of running 32-bit applcations in sysfs Message-ID: <20201028151442.GI13345@gaia> References: <20201027215118.27003-1-will@kernel.org> <20201027215118.27003-6-will@kernel.org> <20201028121506.GG13345@gaia> <20201028122759.GA28091@willie-the-truck> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201028122759.GA28091@willie-the-truck> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On Wed, Oct 28, 2020 at 12:27:59PM +0000, Will Deacon wrote: > On Wed, Oct 28, 2020 at 12:15:07PM +0000, Catalin Marinas wrote: > > On Tue, Oct 27, 2020 at 09:51:17PM +0000, Will Deacon wrote: > > > diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu > > > index b555df825447..19893fb8e870 100644 > > > --- a/Documentation/ABI/testing/sysfs-devices-system-cpu > > > +++ b/Documentation/ABI/testing/sysfs-devices-system-cpu > > > @@ -472,6 +472,14 @@ Description: AArch64 CPU registers > > > 'identification' directory exposes the CPU ID registers for > > > identifying model and revision of the CPU. > > > > > > +What: /sys/devices/system/cpu/aarch32_el0 > > > > Nitpick: should we call this aarch32_el0_present? It's not exactly > > present as we populate it as CPUs come online but it's closer to this > > mask than to the online one. > > I don't think so, because a CPU could be set in this mask but not in the > present mask, which is hugely confusing it it has "present" in the name! How can it end up here but not in the present mask? We populate present early if they have a corresponding DT entry. > > > +Date: October 2020 > > > +Contact: Linux ARM Kernel Mailing list > > > +Description: Identifies the subset of CPUs in the system that can execute > > > + AArch32 (32-bit ARM) applications. If absent, then all or none > > > + of the CPUs can execute AArch32 applications and execve() will > > > + behave accordingly. > > > > What does "accordingly" mean? Normally, we'd get ENOEXEC but here the > > execve() "succeeds" followed by a SIGKILL if it ends up on the wrong > > CPU. > > No; if the file is absent then execve() behaves as it always has. Ah, I missed the "absent" part and got confused. -- Catalin