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@xxxxxxxxxx > > caused regressions on some Chromebooks: > > https://lore.kernel.org/r/Yjyv03JsetIsTJxN@xxxxxxxxxxxxx > > > > 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 <hdegoede@xxxxxxxxxx> 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
