Re: [Xen-devel] [PATCH] vpci: don't allow access to devices not assigned to the domain

[Jan Beulich <jbeulich@xxxxxxxx>]

On 02.09.2019 16:23, Roger Pau Monné  wrote:
> So the problem I found, and that I was trying to address with this
> patch is that a PVH dom0 on AMD hardware finds the iommus by scanning
> the PCI bus, and a Linux dom0 seems to immediately turn off the MSI
> enable control bit on any devices it finds, thus leaving the iommu
> without being able to generate interrupts.
> 
> I can implement the RO stuff, but it seems weird to me. AFAICT the
> only devices owned by Xen should be the serial console, the iommu and
> the HPET maybe. How can hiding those cause anomalies in bus
> enumeration?

Both the serial device and an IOMMU may in principle be func 0 of a
multi-function device. By fully hiding such devices, you also hide
funcs 1-7 afaict. Furthermore, from a tech support pov it seems
rather desirable to have e.g. lspci output in Dom0 to be as complete
as possible.

Jan

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