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=-2.2 required=3.0 tests=FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 2AD96ECE58C for ; Fri, 11 Oct 2019 11:10:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 087E6206CD for ; Fri, 11 Oct 2019 11:10:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727226AbfJKLJ7 (ORCPT ); Fri, 11 Oct 2019 07:09:59 -0400 Received: from ns.iliad.fr ([212.27.33.1]:44702 "EHLO ns.iliad.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726935AbfJKLJ7 (ORCPT ); Fri, 11 Oct 2019 07:09:59 -0400 Received: from ns.iliad.fr (localhost [127.0.0.1]) by ns.iliad.fr (Postfix) with ESMTP id EB584205C8; Fri, 11 Oct 2019 13:09:57 +0200 (CEST) Received: from [192.168.108.37] (freebox.vlq16.iliad.fr [213.36.7.13]) by ns.iliad.fr (Postfix) with ESMTP id D51C52058F; Fri, 11 Oct 2019 13:09:57 +0200 (CEST) Subject: Re: Relax CPU features sanity checking on heterogeneous architectures To: Mark Rutland , Sai Prakash Ranjan References: <20191011105010.GA29364@lakrids.cambridge.arm.com> Cc: MSM , Linux ARM , Ard Biesheuvel , "Suzuki K. Poulose" , Catalin Marinas From: Marc Gonzalez Message-ID: Date: Fri, 11 Oct 2019 13:09:57 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20191011105010.GA29364@lakrids.cambridge.arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Virus-Scanned: ClamAV using ClamSMTP ; ns.iliad.fr ; Fri Oct 11 13:09:58 2019 +0200 (CEST) Sender: linux-arm-msm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org On 11/10/2019 12:50, Mark Rutland wrote: > Before we make any changes, we need to check whether we do actually > handle this variation in a safe way, and we need to consider what this > means w.r.t. late CPU hotplug. > > Even if we can handle variation at boot time, once we've determined the > set of system-wide features we cannot allow those to regress, and I > believe we'll need new code to enforce that. I don't think it's > sufficient to mark these as NONSTRICT, though we might do that with > other changes. > > We shouldn't look at the part number at all here. We care about > variation across CPUs regardless of whether this is big.LITTLE or some > variation in tie-offs, etc. See also the "Unexpected variation in SYS_ID_AA64MMFR0_EL1" thread from a year ago: (that was on msm8998) https://www.spinics.net/lists/arm-kernel/msg691242.html Regards.