Re: [Xen-devel] [PATCH] AMD/IOMMU: revert "amd/iommu: assign iommu devices to Xen"

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 04.06.19 at 10:48, <roger.pau@xxxxxxxxxx> wrote:
> On Mon, Jun 03, 2019 at 07:00:25AM -0600, Jan Beulich wrote:
>> This reverts commit b6bd02b7a877f9fac2de69e64d8245d56f92ab25. The change
>> was redundant with amd_iommu_detect_one_acpi() already calling
>> pci_ro_device().
>> 
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> I think this needs to be squashed together with your `AMD/IOMMU: don't
> "add" IOMMUs` patch, or else PVH dom0 will break because
> update_paging_mode will find devices not behind an IOMMU assigned to
> dom0, thus returning an error and crashing dom0.

I've taken another look (while correcting the other patch, now sent
as v2): update_paging_mode() iterates over all devices the domain
owns. The IOMMU ones, having been subject of an early
pci_ro_device(), should never end up on Dom0's list. And looking at
the code I also can't - for now at least - see how they could get
moved there. In fact I've verified that they take the "override"
path in _setup_hwdom_pci_devices().

Jan



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