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=-6.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 6D8E2C388F7 for ; Tue, 10 Nov 2020 09:29:20 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id E730A20781 for ; Tue, 10 Nov 2020 09:29:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="RmKF1FHn" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E730A20781 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=FOoc+QUEqZmAoB3gtFUEnfobgU2XbkVqLJy6L9owLxw=; b=RmKF1FHnGOWy9t5JPeMu9s5mS /JtgzFeOpHJedrKQb3iSWijtVq0XV5dgGahSC64cfneflqgX0QTuyQ/TjdTlBfgWRmC/L7FQih5XI L30tbdiqUfugHAQSDi7yDaAqQRpR2BFB9pvnhKaKc+TtpjxnE2ygUNxMk1KG4e+2Uy5fWcigb0nRi 8H5y1mzwlDHKKKIMtQADe5p8DuJnnSUrrVBQCouZTKGpKeu0G3hu95SFPEKNlALtVHaozbHIanM44 ULkZ9N86uO9m5mLTv0BxdjGXWpXfaNHAEHULAZC0wLHgoKq/ch1rFlZ6RoIcY0Qk4A7uW9JBvlF3w WxJXihEQA==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kcPxL-000435-Qd; Tue, 10 Nov 2020 09:28:51 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kcPxJ-00042F-HL for linux-arm-kernel@lists.infradead.org; Tue, 10 Nov 2020 09:28:50 +0000 Received: from trantor (unknown [2.26.170.190]) (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 A184320781; Tue, 10 Nov 2020 09:28:45 +0000 (UTC) Date: Tue, 10 Nov 2020 09:28:43 +0000 From: Catalin Marinas To: Greg Kroah-Hartman Subject: Re: [PATCH v2 5/6] arm64: Advertise CPUs capable of running 32-bit applications in sysfs Message-ID: References: <20201109213023.15092-1-will@kernel.org> <20201109213023.15092-6-will@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201110_042849_680302_0F5E26A1 X-CRM114-Status: GOOD ( 18.00 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, kernel-team@android.com, Quentin Perret , Peter Zijlstra , Marc Zyngier , Qais Yousef , Suren Baghdasaryan , Will Deacon , Morten Rasmussen , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Nov 10, 2020 at 08:04:26AM +0100, Greg Kroah-Hartman wrote: > On Mon, Nov 09, 2020 at 09:30:21PM +0000, Will Deacon wrote: > > Since 32-bit applications will be killed if they are caught trying to > > execute on a 64-bit-only CPU in a mismatched system, advertise the set > > of 32-bit capable CPUs to userspace in sysfs. > > > > Signed-off-by: Will Deacon > > --- > > .../ABI/testing/sysfs-devices-system-cpu | 9 +++++++++ > > arch/arm64/kernel/cpufeature.c | 19 +++++++++++++++++++ > > 2 files changed, 28 insertions(+) > > I still think the "kill processes that can not run on this CPU" is crazy I agree it's crazy, though we try to keep the kernel support simple while making it a user-space problem. The alternative is to force-migrate such process to a more capable CPU, potentially against the desired user cpumask. In addition, we'd have to block CPU hot-unplug in case the last 32-bit capable CPU disappears. The only sane thing is not to allow 32-bit processes at all on such hardware but I think we lost that battle ;). -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel