Re: [Xen-devel] [PATCH] x86-64 linux: another adjustment to vmalloc fault handling

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 17 Feb 2006, at 10:38, Jan Beulich wrote:

> Changeset 8847 improved things, but doesn't generally work. We namely 
> experienced problems (when we originally tried the
> same change) with accesses to machine_to_phys_mapping, which (in 
> mfn_to_pfn) is specifically allowed to fault. Hence
> there should not be attempts to fix up faults within the hypervisor 
> range (as for any page table entries obtained there
> no m2p translation exists for the guest, resulting in bogus physical 
> addresses getting used for further fault
> processing, frequently leading to nested faults).
But machine_to_phys_mapping == 0xffff800000000000 while
PAGE_OFFSET == HYPERVISOR_VIRT_END == 0xffff880000000000.

So the patch doesn't really change anything, and 
machine_to_phys_mapping lives below both PAGE_OFFSET and 
HYPERVISOR_VIRT_END anyway.
 -- Keir


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