Re: [Xen-devel] [PATCH] pci: treat class 0 devices as endpoints

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 08.05.18 at 11:33, <roger.pau@xxxxxxxxxx> wrote:
> Class 0 devices are legacy pre PCI 2.0 devices that didn't have a
> class code. Treat them as endpoints, so that they can be handled by
> the IOMMU and properly passed-through to the hardware domain.
> 
> Such device has been seen on a Super Micro server, lspci -vv reports:
> 
> 00:13.0 Non-VGA unclassified device: Intel Corporation Device a135 (rev 31)
>       Subsystem: Super Micro Computer Inc Device 0931
>       Flags: bus master, fast devsel, latency 0, IRQ 11
>       Memory at df222000 (64-bit, non-prefetchable) [size=4K]
>       Capabilities: [80] Power Management version 3
> 
> Arguably this is not a legacy device (since this is a new server), but
> in any case Xen needs to deal with it.

Well, it's a two fold argument: On one hand I agree we ought to be dealing
with class 0. Otoh this particular device is an example to the contrary - we
should try to avoid passing through broken devices: If their designers don't
even get the class code right, what other flaws do we have to expect?
Anyway, this is no objection to the actual code change, I'm merely
unconvinced that the argumentation is plausible.

> Suggested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

Acked-by: Jan Beulich <jbeulich@xxxxxxxx>

Jan


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