From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752771AbcDRNl0 (ORCPT ); Mon, 18 Apr 2016 09:41:26 -0400 Received: from foss.arm.com ([217.140.101.70]:33946 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751189AbcDRNlZ (ORCPT ); Mon, 18 Apr 2016 09:41:25 -0400 Subject: Re: [PATCH 4/5] arm64: Verify CPU errata work arounds on hotplugged CPU To: Will Deacon References: <1459941854-5190-1-git-send-email-suzuki.poulose@arm.com> <1459941854-5190-5-git-send-email-suzuki.poulose@arm.com> <20160414173948.GO4584@arm.com> <570FD817.5050704@arm.com> <5710F653.5070301@arm.com> <20160415141242.GM22906@arm.com> Cc: mark.rutland@arm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, marc.zyngier@arm.com, catalin.marinas@arm.com, Vadim.Lomovtsev@caviumnetworks.com, Andre Przywara From: Suzuki K Poulose Message-ID: <5714E401.1090000@arm.com> Date: Mon, 18 Apr 2016 14:41:21 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: <20160415141242.GM22906@arm.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 15/04/16 15:12, Will Deacon wrote: > On Fri, Apr 15, 2016 at 03:10:27PM +0100, Suzuki K Poulose wrote: >> On 14/04/16 18:49, Suzuki K Poulose wrote: >>> On 14/04/16 18:39, Will Deacon wrote: >>>> On Wed, Apr 06, 2016 at 12:24:13PM +0100, Suzuki K Poulose wrote: >>>>> CPU Errata work arounds are detected and applied to the >>>>> kernel code at boot time and the data is then freed up. >>>>> If a new hotplugged CPU requires a work around which >>>>> was not applied at boot time, there is nothing we can >>>>> do but simply fail the booting. >>>> >>>> Hmm, wouldn't it be better not to free the alternative text for errata >>>> workarounds instead? >>> >>> We could. I don't have a strong opinion. If there are no objections, I could >>> adopt it. >> >> The alternatives have been merged to .init by : >> >> commit 9aa4ec1571da6236 ("arm64: mm: fold alternatives into .init") >> >> Mark, >> >> Do you have any concerns on applying alternatives for CPUs turned online later ? >> We have to revert the patch above to get going > > Well, note that I'm only suggesting that we keep the alternatives for > CPU errata workarounds. So to confirmt, do you mean for now we could do : - Not release the alternatives for errata work arounds. - And retain the check for new erratas, failing the CPUs. And in a follow up series, - Add support for applying errata work arounds later, as we find a new CPU which requires it - and remove the constraint above ? Suzuki