Re: [PATCH 1/1] x86/PCI: Disable exclusion of E820 reserved addresses in some cases

[Mika Westerberg]

On Wed, Feb 16, 2022 at 04:01:21PM +0100, Hans de Goede wrote:
> Some fw has a bug where the PCI bridge window returned by the ACPI
> resources partly overlaps with some other address range, causing issues.
> To workaround this Linux excludes E820 reserved addresses when allocating
> addresses from the PCI bridge window. 2 known examples of such fw bugs are:
> 
> 1. The returned window contains addresses which map to system RAM,
> see commit 4dc2287c1805 ("x86: avoid E820 regions when allocating
> address space").
> 
> 2. The Lenovo X1 carbon gen 2 BIOS has an overlap between an EFI/E820
> reserved range and the ACPI provided PCI bridge window:
>  efi: mem46: [MMIO] range=[0x00000000dfa00000-0x00000000dfa0ffff] (0MB)
>  BIOS-e820: [mem 0x00000000dceff000-0x00000000dfa0ffff] reserved
>  pci_bus 0000:00: root bus resource [mem 0xdfa00000-0xfebfffff window]
> If Linux assigns the overlapping 0xdfa00000-0xdfa0ffff range to a PCI BAR
> then the system fails to resume after a suspend.
> 
> Recently (2019) some systems have shown-up with EFI memmap MMIO entries
> covering the entire ACPI provided PCI bridge window. These memmap entries
> get converted into e820_table entries, causing all attempts to assign
> memory to PCI BARs which have not been setup by the BIOS to fail.
> For example see these dmesg snippets from a Lenovo IdeaPad 3 15IIL 81WE:
>  efi: mem63: [MMIO] range=[0x0000000065400000-0x00000000cfffffff] (1708MB)
>  BIOS-e820: [mem 0x000000004bc50000-0x00000000cfffffff] reserved
>  pci_bus 0000:00: root bus resource [mem 0x65400000-0xbfffffff window]
>  pci 0000:00:15.0: BAR 0: no space for [mem size 0x00001000 64bit]
>  pci 0000:00:15.0: BAR 0: failed to assign [mem size 0x00001000 64bit]
> 
> To fix this, check if the ACPI provided PCI bridge window is fully
> contained within in EFI memmap MMIO region and in that case disable
> the "exclude E820 reserved addresses" workaround, fixing the problem
> of not being able to find free space for unassigned BARs.
> 
> 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://bugzilla.redhat.com/show_bug.cgi?id=2029207
> 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
> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>

Reviewed-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>