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 C010AC433EF for ; Mon, 10 Jan 2022 17:11:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237934AbiAJRL3 (ORCPT ); Mon, 10 Jan 2022 12:11:29 -0500 Received: from sin.source.kernel.org ([145.40.73.55]:49110 "EHLO sin.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232637AbiAJRL3 (ORCPT ); Mon, 10 Jan 2022 12:11:29 -0500 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 sin.source.kernel.org (Postfix) with ESMTPS id D620CCE1677; Mon, 10 Jan 2022 17:11:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 069ADC36AE3; Mon, 10 Jan 2022 17:11:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1641834685; bh=X4tXoAGC6EqJ6PYEuG6VCZ/OpyF8blgVmWjeySllZjQ=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=empKVpZSr2IPSLiNwSMhcQyNj0YdWaPaD1kHUE2YOI95Bc0/xHllJHIJ2w1eEzItk /Ag9iEjQ3tvNVUjQAshIVIgB45mBrjIjVtKRi8YNTDjz+bQBRZ5zhIrAEbIfK2cl/O nV/x3qj6KAdajx7F49Vj2GjPUATphHfNsrWBQDLX+v9iT6ERZGqZAYtL/h0G7KN8d2 rNnds4Y5qmTQl76eEdPBPUi5zK+i2Wv/Vrn1khMtXibf5x9NkOZuT+e5ti4YCF7yAT V2HXSP8zsyVFd650EoK0kLpV1tLdSy+ICmWVXJYdIw1fKPjUe886ijAQihynoApjBy jEAvK1ta7unvg== Date: Mon, 10 Jan 2022 11:11:23 -0600 From: Bjorn Helgaas To: Hans de Goede Cc: "Rafael J . Wysocki" , Mika Westerberg , Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= , Bjorn Helgaas , Myron Stowe , Juha-Pekka Heikkila , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H . Peter Anvin" , linux-acpi@vger.kernel.org, linux-pci@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, Benoit =?iso-8859-1?Q?Gr=E9goire?= , Hui Wang , stable@vger.kernel.org, "Rafael J . Wysocki" Subject: Re: [PATCH v6] x86/PCI: Ignore E820 reservations for bridge windows on newer systems Message-ID: <20220110171123.GA60297@bhelgaas> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org On Mon, Jan 10, 2022 at 12:41:37PM +0100, Hans de Goede wrote: > Hi All, > > On 12/17/21 15:13, Hans de Goede wrote: > > Some BIOS-es contain a bug where they add addresses which map to system > > RAM in the PCI host bridge window returned by the ACPI _CRS method, see > > commit 4dc2287c1805 ("x86: avoid E820 regions when allocating address > > space"). > > > > To work around this bug Linux excludes E820 reserved addresses when > > allocating addresses from the PCI host bridge window since 2010. > > > > Recently (2019) some systems have shown-up with E820 reservations which > > cover the entire _CRS returned PCI bridge memory window, causing all > > attempts to assign memory to PCI BARs which have not been setup by the > > BIOS to fail. For example here are the relevant dmesg bits from a > > Lenovo IdeaPad 3 15IIL 81WE: > > > > [mem 0x000000004bc50000-0x00000000cfffffff] reserved > > pci_bus 0000:00: root bus resource [mem 0x65400000-0xbfffffff window] > > > > The ACPI specifications appear to allow this new behavior: > > > > The relationship between E820 and ACPI _CRS is not really very clear. > > ACPI v6.3, sec 15, table 15-374, says AddressRangeReserved means: > > > > This range of addresses is in use or reserved by the system and is > > not to be included in the allocatable memory pool of the operating > > system's memory manager. > > > > and it may be used when: > > > > The address range is in use by a memory-mapped system device. > > > > Furthermore, sec 15.2 says: > > > > Address ranges defined for baseboard memory-mapped I/O devices, such > > as APICs, are returned as reserved. > > > > A PCI host bridge qualifies as a baseboard memory-mapped I/O device, > > and its apertures are in use and certainly should not be included in > > the general allocatable pool, so the fact that some BIOS-es reports > > the PCI aperture as "reserved" in E820 doesn't seem like a BIOS bug. > > > > So it seems that the excluding of E820 reserved addresses is a mistake. > > > > Ideally Linux would fully stop excluding E820 reserved addresses, > > but then the old systems this was added for will regress. > > Instead keep the old behavior for old systems, while ignoring > > the E820 reservations for any systems from now on. > > > > Old systems are defined here as BIOS year < 2018, this was chosen to make > > sure that E820 reservations will not be used on the currently affected > > systems, while at the same time also taking into account that the systems > > for which the E820 checking was originally added may have received BIOS > > updates for quite a while (esp. CVE related ones), giving them a more > > recent BIOS year then 2010. > > > > BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=206459 > > BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=1868899 > > BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=1871793 > > BugLink: https://bugs.launchpad.net/bugs/1878279 > > BugLink: https://bugs.launchpad.net/bugs/1931715 > > BugLink: https://bugs.launchpad.net/bugs/1932069 > > BugLink: https://bugs.launchpad.net/bugs/1921649 > > Cc: Benoit Grégoire > > Cc: Hui Wang > > Cc: stable@vger.kernel.org > > Reviewed-by: Mika Westerberg > > Acked-by: Rafael J. Wysocki > > Acked-by: Bjorn Helgaas > > Signed-off-by: Hans de Goede > > --- > > Changes in v6: > > - Remove the possibility to change the behavior from the commandline > > because of worries that users may use this to paper over other problems > > ping ? Thanks, Hans. Maybe I'm quixotic, but I'm still hoping for an approach based on firmware behavior instead of firmware date. If nobody else tries, I will eventually try myself, but I don't have any ETA. Bjorn