[Xen-devel] Re: A race condition in xenlinux exit_mmap

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 1 Aug 2006, at 10:21, Li, Xin B wrote:

> 2 possible solutions are:
> 1) call arch_exit_mmap after unmap_vmas.
> 2) unmap foreign mapped pages before calling arch_exit_mmap, and then 
> we
> can do the normal cleanup jobs.
A longer term plan is to add an explicit flag to PTEs that are foreign 
mappings (and so are not refcounted). However, I think the easiest 
solution for now is to add a flag to mmu_context structure indicating 
whether this mm has ever had any foreign mappings (so you would set it 
in direct_remap_pfn_range()). If it has then we do not call mm_unpin() 
from _arch_exit_mmap() -- doing so is only an optimisation which we can 
simply not do for the very small number of mm's that have foreign 
mappings.
Do you mind creating a patch to do this? I can send you more details if 
you like.
 -- Keir


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