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[Xen-devel] implicit grant unmap

  • To: "xen-devel" <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • From: "King, Steven R" <steven.r.king@xxxxxxxxx>
  • Date: Tue, 14 Feb 2006 13:07:59 -0800
  • Delivery-date: Tue, 14 Feb 2006 21:20:09 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: AcYxqrvoi3owSMCVQ6iQco2bGX0aEw==
  • Thread-topic: implicit grant unmap

Hello All,
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?


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