Re: [Xen-devel] [PATCH] amd iommu: re-enable iommu msi if dom0 disabled it

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 08.06.12 at 15:28, Wei Wang <wei.wang2@xxxxxxx> wrote:
> I found that recent dom0 (e.g 3.4 pv_ops) disables iommu msi capability 
> for some reasons and iommu cannot generate any interrupts in this case.

That shouldn't happen in the first place, and hence should be fixed
in the kernel.

> Attached patch re-enables it in device assignment.

I'm not really keen on taking this - it's silently working around a
problem, and doesn't appear to cover the case where Dom0
would have its I/O got through the IOMMU as well.

If anything, I'd be much more in favor of hiding the entire config
space of the IOMMU device from Dom0 (or at least making it
read-only), which admittedly might be a little tricky. So first of
all let's understand whether this can't reasonably be fixed in
Linux.

Jan


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