From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752942AbbLPL3U (ORCPT ); Wed, 16 Dec 2015 06:29:20 -0500 Received: from foss.arm.com ([217.140.101.70]:54863 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750832AbbLPL3T (ORCPT ); Wed, 16 Dec 2015 06:29:19 -0500 Date: Wed, 16 Dec 2015 11:29:15 +0000 From: Will Deacon To: "Suzuki K. Poulose" Cc: mark.rutland@arm.com, catalin.marinas@arm.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, marc.zyngier@arm.com Subject: Re: [RFC PATCH v3 4/8] arm64: Handle early CPU boot failures Message-ID: <20151216112914.GF4308@arm.com> References: <1449655039-22022-1-git-send-email-suzuki.poulose@arm.com> <1449655039-22022-5-git-send-email-suzuki.poulose@arm.com> <20151215115518.GE9452@arm.com> <56713F76.8080907@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56713F76.8080907@arm.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 16, 2015 at 10:39:50AM +0000, Suzuki K. Poulose wrote: > On 15/12/15 11:55, Will Deacon wrote: > >On Wed, Dec 09, 2015 at 09:57:15AM +0000, Suzuki K. Poulose wrote: > > >> /* > >> * Initial data for bringing up a secondary CPU. > >>+ * @stack - sp for the secondary CPU > >>+ * @status - Result passed back from the secondary CPU to > >>+ * indicate failure. > >> */ > >> struct secondary_data { > >> void *stack; > >>-}; > >>+ unsigned long status; > >>+} ____cacheline_aligned; > > > >Why is this necessary? > > That was based on a suggestion from Mark Rutland here: > > https://lkml.org/lkml/2015/12/1/580 That thread is talking about the CWG, which is not the same thing as ____cacheline_aligned. Given that the architectural maximum for the CWG is 2K, we can probably get away with allocating the status field amongst the head.S text instead (which we know will be clean). Since SMP boot is serialised, that should be sufficient, right? Will