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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 30D32C433EF for ; Fri, 18 Mar 2022 21:26:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231135AbiCRV2I (ORCPT ); Fri, 18 Mar 2022 17:28:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50982 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241202AbiCRV2F (ORCPT ); Fri, 18 Mar 2022 17:28:05 -0400 Received: from mail-pj1-x102a.google.com (mail-pj1-x102a.google.com [IPv6:2607:f8b0:4864:20::102a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5B20012E741; Fri, 18 Mar 2022 14:26:46 -0700 (PDT) Received: by mail-pj1-x102a.google.com with SMTP id b8so8375241pjb.4; Fri, 18 Mar 2022 14:26:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=ngACJmeVV9pPVZzYzpTofY7PpGPGJ4tyVyA//CfbKMw=; b=I5DKGYi5JVESFPGE8929b6D4feB7CmGqV1QTUVY144tOMh4r8VrXHqZYItH1JtzF6+ xWiu7ZgTBvNe0py4k0xnQPYWVt08Ps//7Uk7cGi5dmxN4vlrRAfaAZpeHGx+9HPDG2bf ZX+dZS8JGMK4CpcUosDYfgb8UdEC9ZBcT00t90sGBjfG+5fw4yOjmP8lZKXjhOBjoTE4 zjsMNE3l5CkEIZDOJ+JM/NyhH5T7T+YgeSdP1JGi+7uL11u3YtdaUq/LP9gwgOs/pNMN gXx497yV8ujjTMkJI7iHQYkTtIBnPzR00RZUmH4DbxVvsQ1cek1HqBVJ/mfgv52w1FlP 1hPg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=ngACJmeVV9pPVZzYzpTofY7PpGPGJ4tyVyA//CfbKMw=; b=UAWiIZpvtcbHHhGvvU5gy+Yca7Jmc9q2oWc0xlPSQvQKC8uY1AVjuVSMM88FJO35C0 VZ3ZjNz6IaypNDjfWKipAlu3vsgO7lRe9lBJJksHDjHZ6SXC2amxgvrfS309gmHsh02L uGoRXD4CmnKTksawLqa2sc64PTEJYUezAR9gFUXLK/n7AvhME8Fiey0E39uchEuEs0Uu l0TZabcpjWPj/ainb+WddWD0kpqUeQYfh9z7k5e7FiurcEQXUjOC+rhn/SI6jW6V3CjA ADe+icdOHpTY378LAN883HxR5YaYFcMU8lOzc5fMmWfrmjXzno9HaGiTpRpMsP9vGoVr x2uw== X-Gm-Message-State: AOAM533cNq6fUINvPoxScFzlZ9+TKiCCr79quwfb5MdJCtqw6aWwBbz5 uNNnaxeSbNA3HnZhbcGiyKsElire0qg= X-Google-Smtp-Source: ABdhPJy+etAMlosAPHBEubVULFhPikXO3lrAyit0p0AdzhMJ1owsnFVy8PWq4CVWA2INxOFRIJ43pA== X-Received: by 2002:a17:90b:4b8a:b0:1c6:35d1:4418 with SMTP id lr10-20020a17090b4b8a00b001c635d14418mr23227227pjb.176.1647638805484; Fri, 18 Mar 2022 14:26:45 -0700 (PDT) Received: from [10.67.48.245] ([192.19.223.252]) by smtp.googlemail.com with ESMTPSA id o3-20020a639203000000b003810e49ff4fsm8884375pgd.1.2022.03.18.14.26.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 18 Mar 2022 14:26:44 -0700 (PDT) Subject: Re: [PATCH] net: bcmgenet: Use stronger register read/writes to assure ordering To: Jakub Kicinski , Florian Fainelli Cc: Peter Robinson , Jeremy Linton , netdev@vger.kernel.org, opendmb@gmail.com, davem@davemloft.net, bcm-kernel-feedback-list@broadcom.com, linux-kernel@vger.kernel.org References: <20220310045358.224350-1-jeremy.linton@arm.com> <2167202d-327c-f87d-bded-702b39ae49e1@gmail.com> <472540d2-3a61-beca-70df-d5f152e1cfd1@gmail.com> <20220318122017.24341eb1@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> From: Florian Fainelli Message-ID: <082a7743-2eb8-c067-e41d-2a3acca5c056@gmail.com> Date: Fri, 18 Mar 2022 14:26:36 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: <20220318122017.24341eb1@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 3/18/22 12:20 PM, Jakub Kicinski wrote: > On Fri, 18 Mar 2022 12:01:20 -0700 Florian Fainelli wrote: >> Given the time crunch we should go with Jeremy's patch that uses >> stronger I/O access method and then we will work with Jeremy offline to >> make sure that our version of GCC12 is exactly the same as his, as well >> as the compiler options (like -mtune/-march) to reproduce this. >> >> If we believe this is only a problem with GCC12 and 5.17 in Fedora, then >> I would be inclined to remove the Fixes tag such that when we come up >> with a more localized solution we do not have to revert "net: bcmgenet: >> Use stronger register read/writes to assure ordering" from stable >> branches. This would be mostly a courtesy to our future selves, but an >> argument could be made that this probably has always existed, and that >> different compilers could behave more or less like GCC12. > > Are you expecting this patch to make 5.17? If Linus cuts final this > weekend, as he most likely will, unless we do something special the > patch in question will end up getting merged during the merge window. > Without the Fixes tag you'll need to manually instruct Greg to pull > it in. Is that the plan? Maybe I should have refrained from making that comment after all :) Having the Fixes: tag dramatically helps with getting this patch applied all the way to the relevant stable trees and surely correctness over speed should prevail. If we want to restore the performance loss (with the onus on Doug and I to prove that there is a performance drop), then we could send a fix with the appropriate localized barrier followed by a revert of Jeremy's patch. And if we cared about getting those two patches applied to stable, we would tag them with the appropriate Fixes tag. It looks like there are a few 'net' changes that showed up, are you going to send a pull request to Linus before 5.17 final is cut? -- Florian