[Xen-devel] [PATCH 0/3] AMD/IOMMU: re-work mode updating

[Jan Beulich <jbeulich@xxxxxxxx>]

update_paging_mode() in the AMD IOMMU code expects to be invoked with
the PCI devices lock held. The check occurring only when the mode
actually needs updating, the violation of this rule by the majority
of callers did go unnoticed until per-domain IOMMU setup was changed
to do away with on-demand creation of IOMMU page tables.

Unfortunately the only half way reasonable fix to this that I could
come up with requires more re-work than would seem desirable at this
time of the release process, but addressing the issue seems
unavoidable to me as its manifestation is a regression from the
IOMMU page table setup re-work. The change also isn't without risk
of further regressions - if in patch 2 I've missed a code path that
would also need to invoke the new hook, then this might mean non-
working guests (with passed-through devices on AMD hardware).

1: AMD/IOMMU: don't needlessly trigger errors/crashes when unmapping a page
2: introduce GFN notification for translated domains
3: AMD/IOMMU: use notify_dfn() hook to update paging mode

Jan

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