On Tue, Apr 5, 2022 at 1:05 PM Brown, Len <len.brown@xxxxxxxxx> wrote: > > Is it possible for ACPI to be aware that CXL on that system doesn't support S3, and for ACPI to thus simply not export S3? The ACPI domain has a chance to be aware of CXL devices attached at boot and were configured into the System Memory Map. However, there may be caveats that limit device visibility like platform firmware only scans CXL devices directly attached to root ports, not behind switches. It would be welcome if there was an ACPI data structure to indicate "device-X is in scope for S3" which would mean that it has aux power and all HDM decoders (the registers that enable access to CXL memory) are restored by the BIOS before OS resume begins. Absent that the OS can only assume that the BIOS has no knowledge of any HDM configurations that were defined at run time by the OS, like after hotplug, or configurations that the OS rewrote by triggering a secondary bus reset to unlock what the BIOS had locked and put into the EFI memory map.
