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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 88A2AC3F68F for ; Fri, 31 Jan 2020 21:44:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5ACB2215A4 for ; Fri, 31 Jan 2020 21:44:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726561AbgAaVoV (ORCPT ); Fri, 31 Jan 2020 16:44:21 -0500 Received: from mga12.intel.com ([192.55.52.136]:60613 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726105AbgAaVoV (ORCPT ); Fri, 31 Jan 2020 16:44:21 -0500 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by fmsmga106.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 31 Jan 2020 13:44:21 -0800 X-IronPort-AV: E=Sophos;i="5.70,387,1574150400"; d="scan'208";a="377464364" Received: from agluck-desk2.sc.intel.com (HELO agluck-desk2.amr.corp.intel.com) ([10.3.52.68]) by orsmga004-auth.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 31 Jan 2020 13:44:20 -0800 Date: Fri, 31 Jan 2020 13:44:19 -0800 From: "Luck, Tony" To: Pavel Machek Cc: Greg Kroah-Hartman , linux-kernel@vger.kernel.org, stable@vger.kernel.org, Peter Zijlstra , Fenghua Yu , "David S. Miller" , Sasha Levin Subject: Re: [PATCH 4.19 36/55] drivers/net/b44: Change to non-atomic bit operations on pwol_mask Message-ID: <20200131214419.GA19569@agluck-desk2.amr.corp.intel.com> References: <20200130183608.563083888@linuxfoundation.org> <20200130183615.120752961@linuxfoundation.org> <20200131125730.GA20888@duo.ucw.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200131125730.GA20888@duo.ucw.cz> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 31, 2020 at 01:57:31PM +0100, Pavel Machek wrote: > And I wonder if this is even good idea for mainline. x86 architecture > is here for long time, and I doubt Intel is going to break it like > this. Do you have documentation pointer? Intel isn't breaking this legacy behaviour. But it is building h/w that allows s/w to opt-in to a mode that will generate an #AC trap for a split lock. One such processor ("Icelake") is already shipping. Some Linux use cases (real-time) really, really want to avoid the cost of a split-lock. There's a patch in TIP that will enable this #AC on split-lock mode on processors that support it. Thus it's a good idea to clean up any places in the kernel that will cause #AC when that mode is enabled. I think mainline should be taking any patches for split lock cleanup. Stable is a different question. The patch to enable the #AC should not be backported to stable. So the only way an old kernel would hit this would be if the BIOS enabled the #AC. Really that should only happen on a system where the developers have validated that the entire software stack has been checked for split locks. Is net/b44 a device that is still being included on current systems? Or is it a legacy device that has been superceeded by something else? If there isn't going to be a b44 on an Icelake or newer system, then perhaps we should not worry so much about fixing the driver. -Tony