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 EFF33C433F5 for ; Tue, 19 Apr 2022 15:03:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351960AbiDSPGb (ORCPT ); Tue, 19 Apr 2022 11:06:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57828 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1352313AbiDSPGa (ORCPT ); Tue, 19 Apr 2022 11:06:30 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D7273393E3; Tue, 19 Apr 2022 08:03:47 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 6EEBD615A3; Tue, 19 Apr 2022 15:03:47 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 87D38C385BB; Tue, 19 Apr 2022 15:03:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1650380626; bh=2QAhuc2XWcc3cQISqAxXYVsD0D9u3Zzv0U665e9wblg=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=sH1xvpevcqmRCg1FQs9IreiBFSyKwR9KorOvczKSfsvKZO7JGQBU8RSWYJxInjJUu aJf/p8r9ijLvNlXeoY517zB6xvdx5upsf50wP3LqXQC4anvduDfEH6789kmOrmHtyV T5ArVtogHhSLnz2Pwmm/nvIyf6YoALuaWLHJAwl2wepbhlk9T6H0v/GUYRK/A5UPri Xu37ZyCt2GzgaltOoY8YxFRaUWCtyebFlC12zaLez0zG2Bf66Md7rVha4m7YXd16kw kkLB1wf308TXgd5ocdZjKf43CtD7hM/3yiQUvLhym6/eIWI8yIUtm/pR9OgssQ7gwu A7+M2sRQwXkng== Date: Tue, 19 Apr 2022 10:03:44 -0500 From: Bjorn Helgaas To: Hans de Goede Cc: "Rafael J . Wysocki" , Borislav Petkov , "H . Peter Anvin" , Ingo Molnar , Mika Westerberg , Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= , Myron Stowe , Juha-Pekka Heikkila , Benoit =?iso-8859-1?Q?Gr=E9goire?= , Hui Wang , Kai-Heng Feng , linux-acpi@vger.kernel.org, linux-pci@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, Bjorn Helgaas Subject: Re: [PATCH v2 0/3] x86/PCI: Log E820 clipping Message-ID: <20220419150344.GA1198281@bhelgaas> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Tue, Apr 19, 2022 at 11:59:17AM +0200, Hans de Goede wrote: > On 1/1/70 01:00, Bjorn Helgaas wrote: > > This is still work-in-progress on the issue of PNP0A03 _CRS methods that > > are buggy or not interpreted correctly by Linux. > > > > The previous try at: > > https://lore.kernel.org/r/20220304035110.988712-1-helgaas@kernel.org > > caused regressions on some Chromebooks: > > https://lore.kernel.org/r/Yjyv03JsetIsTJxN@sirena.org.uk > > > > This v2 drops the commit that caused the Chromebook regression, so it also > > doesn't fix the issue we were *trying* to fix on Lenovo Yoga and Clevo > > Barebones. > > > > The point of this v2 update is to split the logging patch into (1) a pure > > logging addition and (2) the change to only clip PCI windows, which was > > previously hidden inside the logging patch and not well documented. > > > > Bjorn Helgaas (3): > > x86/PCI: Eliminate remove_e820_regions() common subexpressions > > x86: Log resource clipping for E820 regions > > x86/PCI: Clip only host bridge windows for E820 regions > > Thanks, the entire series looks good to me: > > Reviewed-by: Hans de Goede Thank you! > So what is the plan to actually fix the issue seen on some Lenovo models > and Clevo Barebones ? As I mentioned previously I think that since all > our efforts have failed so far that we should maybe reconsider just > using DMI quirks to ignore the E820 reservation windows for host bridges > on affected models ? I have been resisting DMI quirks but I'm afraid there's no other way. I think the web we've gotten into, where vendors have used E820 to interact with _CRS in incompatible and undocumented ways, is not sustainable. I'm not aware of any spec that says the OS should use E820 to clip things out of _CRS, so I think the long term plan should be to decouple them by default. Straw man: - Disable E820 clipping by default. - Add a quirk to enable E820 clipping for machines older than X, e.g., 2023, to avoid breaking machines that currently work. - Add quirks to disable E820 clipping for individual machines like the Lenovo and Clevos that predate X, but E820 clipping breaks them. - Add quirks to enable E820 clipping for individual machines like the Chromebooks (and probably machines we don't know about yet) that have devices that consume part of _CRS but are not enumerable. - Communicate this to OEMs to try to prevent future machines that need quirks. Bjorn