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=-8.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 32B5CC388F7 for ; Thu, 29 Oct 2020 00:56:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DD61C20790 for ; Thu, 29 Oct 2020 00:56:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603932960; bh=wHB2qzDM/Qb93kjop/F95XLwJpWFV6M4N5dLHppuCqk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=O+LitdHrCd6FZEWGaeMaNeredBf/bltM590SBaVKhIKezLf8d553kuodWqYF5E+gW GRonzUKesFanMr/g1voZB5E8FAoBpVNuNwywC1sn5RF9+EoASIa6Gd0EJAuGCrHR0p jmRMUcIa8WtJA6cl/Jrnfh5su1OkVIpPMESEt1xk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731671AbgJ1WRj (ORCPT ); Wed, 28 Oct 2020 18:17:39 -0400 Received: from mail.kernel.org ([198.145.29.99]:60544 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731649AbgJ1WRj (ORCPT ); Wed, 28 Oct 2020 18:17:39 -0400 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 5D82F24707; Wed, 28 Oct 2020 12:28:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603888085; bh=wHB2qzDM/Qb93kjop/F95XLwJpWFV6M4N5dLHppuCqk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=v8gRsUcli2D+GnLRGa0996eRVnlWuQ3RAX6l64NE/2/WQO51OmappChbdbq1/Nj1v dPCdSwT1R43FShP4UahdPV6ysOeBtGXvixc1VWxgO61qGJbuL2yKUU68a9+Hjf7Q9s 8TS17/rwfyCmkgDby9wogKQXJHYLtpO6sqGm6aG8= Date: Wed, 28 Oct 2020 12:27:59 +0000 From: Will Deacon To: Catalin Marinas 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: <20201028122759.GA28091@willie-the-truck> References: <20201027215118.27003-1-will@kernel.org> <20201027215118.27003-6-will@kernel.org> <20201028121506.GG13345@gaia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201028121506.GG13345@gaia> 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 12:15:07PM +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! > > +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. Will