On 10/11/21 9:53 PM, Mika Westerberg wrote:
Hi Hans, On Mon, Oct 11, 2021 at 11:05:31AM +0200, Hans de Goede wrote:Some BIOS-es contain a bug where they add addresses which map to system RAM in the PCI bridge memory window returned by the ACPI _CRS method, see commit 4dc2287c1805 ("x86: avoid E820 regions when allocating address space"). To avoid this Linux by default excludes E820 reservations when allocating addresses since 2010. Windows however ignores E820 reserved regions for PCI mem allocations, so in hindsight Linux honoring them is a problem. Recently (2020) 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: [ 0.000000] BIOS-e820: [mem 0x000000004bc50000-0x00000000cfffffff] reserved [ 0.557473] pci_bus 0000:00: root bus resource [mem 0x65400000-0xbfffffff window] Ideally Linux would fully stop honoring E820 reservations for PCI mem allocations, but then the old systems this was added for will regress. Instead keep the old behavior for old systems, while ignoring the E820 reservations like Windows does for any systems from now on. Old systems are defined here as BIOS year < 2018, this was chosen to make sure that pci_use_e820 will not be set on the currently affected systems, while at the same time also taking into account that the systems for which the E820 checking was orignally added may have received BIOS updates for quite a while (esp. CVE related ones), giving them a more recent BIOS year then 2010. Also add pci=no_e820 and pci=use_e820 options to allow overriding the BIOS year heuristic. 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 <benoitg@xxxxxxxx> Cc: Hui Wang <hui.wang@xxxxxxxxxxxxx> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>Thanks for fixing this! Few comments below. Otherwise looks good, Reviewed-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
Thanks for fixing this! We almost reach a solution. :-) Thanks, Hui.
