Re: [PATCH 0/3] iommu/vt-d bad RMRR workarounds

From: Barret Rhoden
Date: Fri Dec 13 2019 - 09:31:41 EST

On 12/11/19 9:43 PM, Lu Baolu wrote:
The VT-d spec defines the BIOS considerations about RMRR in section 8.4:

BIOS must report the RMRR reported memory addresses as reserved (or as
EFI runtime) in the system memory map returned through methods such as
INT15, EFI GetMemoryMap etc.

So we should treat it as firmware bug if the RMRR range is not mapped as
RESERVED in the system memory map table.

As for how should the driver handle this case, ignoring buggy RMRR with
a warning message might be a possible choice.

Agreed, firmware should not be doing this. My first patch just skips those entries, instead of aborting DMAR processing, and keeps the warning.

So long as the machine still boots in a safe manner, I'm reasonably happy.