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,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 E6ED3C56201 for ; Wed, 28 Oct 2020 22:07:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 89AA32473C for ; Wed, 28 Oct 2020 22:07:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603922877; bh=wHsCbiDe/qhudX6Zti2IFuMsNRMvpNSZBq+nyahvtYg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=fN57aWN3baBZHq160bN2PHKntv6+mpCsyo0YeBWV4TX66KbTzFcUaZLgGQlC1MNAX Wa6slXPddIpnXnh4i8T9Nwnus5I4I+/tuGbeKkUlP+0DIfxxXyTr8yLs7Xw5gtLS5y TpIENgkF87Wv1EsyfLpzeYe52cfHNU7Pmvhexk44= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730097AbgJ1WH0 (ORCPT ); Wed, 28 Oct 2020 18:07:26 -0400 Received: from mail.kernel.org ([198.145.29.99]:52324 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730088AbgJ1WHX (ORCPT ); Wed, 28 Oct 2020 18:07:23 -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 CF6FD2474F; Wed, 28 Oct 2020 15:36:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603899363; bh=wHsCbiDe/qhudX6Zti2IFuMsNRMvpNSZBq+nyahvtYg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=vsiiPL1x1DFxGcJ6AzZk/38uVHuL2ihjns5//nPQqbjAG1PzwNSZnNwQilgNqZRCG ZwyEJ5xLuKnBX/En/dWqQ1OLfqaa7A3jDDJQyTsmZKdDmGHZ/hAcd1zTL2f+pOqehU tyqKTMVZ+X4eCNPhvz172GhIzzJNklg86KYoJFsU= Date: Wed, 28 Oct 2020 15:35:58 +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: <20201028153557.GA29024@willie-the-truck> References: <20201027215118.27003-1-will@kernel.org> <20201027215118.27003-6-will@kernel.org> <20201028121506.GG13345@gaia> <20201028122759.GA28091@willie-the-truck> <20201028151442.GI13345@gaia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201028151442.GI13345@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 03:14:43PM +0000, Catalin Marinas wrote: > 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. I was under the impression that physical CPU hotplug with ACPI would clear the entry in the present mask, but I can't say I have any machines that I can test that with and it looks like it might only be implemented for x86 at the moment. That said, it looks like cpu_die_early() also marks CPUs as not being present and this can happen due to a late capability conflict. Will