Re: [Xen-devel] implicit grant unmap

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 14 Feb 2006, at 21:07, King, Steven R wrote:

> I'm contemplating ways to avoid the domain_crash() in mm.c line ~615
> without requiring new OS hooks.  This crash occurs when the operating
> system writes a zero to the PTE for a grant mapping without an explicit
> Xen call to unmap.
>
> In hacking around, it seems the problem is this:  When the mapping PTE
> gets squashed, Xen's cleanup_writable_pagetable() has no way to find 
> the
> correct maptrack entry for the affected mapping.  Consequently, the
> grant mapping is not properly cleaned-up.
>
> Sound correct?  Are there worse problems here?
That's right. That grant will hang around until the domain is 
destroyed, at which point the grant is cleaned up by 
gnttab_release_mappings().
 -- Keir


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