[Xen-devel] bug, bad page free with hvm guest after commits about AMD IOMMU

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

Hi,

With the last xen-unstable, when I try to run a HVM guest, the vgabios
did not display anything on the screen (it is only white), and Xen
print this:

(XEN) mm.c:2137:d0 Error pfn 0: rd=ffff83023e8a0000,
od=ffff83022f5f3000, caf=8000000000000001, taf=7400000000000001
(XEN) memory.c:196:d0 Bad page free for domain 24
(XEN) mm.c:2137:d0 Error pfn 0: rd=ffff83023e8a0000,
od=ffff83022f5f3000, caf=8000000000000001, taf=7400000000000001
(XEN) memory.c:196:d0 Bad page free for domain 24
...

I found the issue come from one of this commits:
5cd3681 x86/mm: Add a generic interface for vtd and amd iommu p2m
sharing. Also introduce a new parameter (iommu=sharept) to enable this
6b3faa6 x86/mm: Implement p2m table sharing for AMD IOMMU.
8d771f6 x86/mm: add AMD IOMMU control bits to p2m entries.
2452ae6 x86/mm: Move p2m type into bits of the PTE that the IOMMU doesn't use.

This happened on two machines:
Intel(R) Core(TM) i7 CPU       M 620  @ 2.67GHz
Intel(R) Xeon(R) CPU           X3450  @ 2.67GHz

-- 
Anthony PERARD

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