Re: [PATCH 1/3] xen/pci: do not register devices outside of PCI segment scope

Jan Beulich
2025-01-13T07:17:23Z

On 10.01.2025 15:01, Roger Pau Monne wrote:
> The PCI segment value is limited to 16 bits, however there are buses like VMD
> that fake being part of the PCI topology by adding segment with a number
> outside the scope of the PCI firmware specification range (>= 0x10000). The
> MCFG ACPI Table "PCI Segment Group Number" field is defined as having a 16 bit
> width.
>
> Attempting to register or manage those devices with Xen would result in errors
> at best, or overlaps with existing devices living on the truncated equivalent
> segment values.
>
> Skip notifying Xen about those devices.

Hmm, is simply omitting the notification really all it takes? How would Xen
manage MSI / MSI-X, for example, without knowing of the device? As per the
BoF on the summit in Prague(?), I continue to think we need partial driver
logic in Xen for VMD ...

Jan