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xen-devel
[Xen-devel] Re: A race condition in xenlinux exit_mmap
Hi, Keir,
Why not just reuse VM_FOREIGN(blktap uses this flag to represent foreign
mapped vma) flag to unmap the foreign mapped pages before call
arch_exit_mmap? This could be a simple alternative.
_______________________________________________________
Best Regards,
hanzhu
Keir Fraser дµÀ:
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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