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Re: [Xen-devel] implicit grant unmap

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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