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Re: [Xen-devel] [PATCH v4 4/5] amd/iommu: assign iommu devices to Xen

>>> On 14.11.18 at 13:33, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 14/11/2018 11:57, Roger Pau Monne wrote:
>> AMD IOMMU devices are exposed on the PCI bus, and thus are assigned by
>> default to the hardware domain. This can cause issues because the
>> IOMMU devices are not behind an IOMMU, and conceptually it's also wrong
>> to give the hardware domain ownership of those devices since they are
>> in use by Xen.
>> Fix this by assigning the PCI IOMMU devices to Xen.
>> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> This is unfortunately a symptom of much more basic bug in Xen.
> Particularly on recent server parts, there are many PCI devices which
> represent processor internals and aren't safe to give even to dom0.

Well, yes, some perhaps.

> There should be a whitelist of devices we consider safe, not a blacklist
> of those we know to be unsafe.

Such an approach would, I'm afraid, be workable only if vendors
(pro)actively communicated properties and device IDs, such that
we would not constantly lag behind what's on the market.


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