Re: [Xen-devel] Xen-unstable-staging: Xen BUG at iommu_map.c:455

[Tim Deegan <tim@xxxxxxx>]

[Trimmed egregious quoting]

At 22:35 +0100 on 11 Apr (1428791713), Andrew Cooper wrote:
> I am not certain that it is the correct way to fix the issue, nor that
> the ioreq server code is the only way to trigger it.  There are several
> ways to shoot a gfn mapping from the guests physmap.
> 
> At least we now understand why it happens.  I will defer to others CC'd
> on this thread for their opinions in the matter.

The patch semes like a pretty good check to me, though I'm not
convinced it's race-free.  At the least I'd cache the m2p lookup so we
use the same value for the checks and the map_page() call. 

And IMO update_paging_mode() ought to log and reject bogus GFNs as
well.

Cheers,

Tim.

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