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

On Mon, May 14, 2018 at 06:46:08AM -0600, Jan Beulich wrote:
> >>> 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>


Since I also have another patch already Acked, I guess I will maintain
my for-4.12 branch until the tree opens again.


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