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

["Li, Xin B" <xin.b.li@xxxxxxxxx>]

yes, elegant fix is not easy.

-Xin

---

From: bjthomas3@xxxxxxxxx [mailto:bjthomas3@xxxxxxxxx] On Behalf Of Ben Thomas
Sent: 2006年8月1日 21:03
To: Li, Xin B
Cc: hanzhu@xxxxxxxxxxx; xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-devel] Re: A race condition in xenlinux exit_mmap

Xin,

I'm attaching a patch that we've been using since late May/early June to address an "Eeek" issues. Since we applied the patch, we haven't seen the issue.  As this was some time ago, I cannot recall if this is the same problem that you're seeing now. The patch wasn't submitted, as it isn't particularly clean. It's one of the many "some day soon" patches that we need to get resubmitted after a bit more work. I attach it here, not because I believe that it is "the answer", but as a data point for you.

-b

On 8/1/06, Keir Fraser <Keir.Fraser@xxxxxxxxxxxx > wrote:

On 1 Aug 2006, at 11:39, Li, Xin B wrote:

>> Do you mind creating a patch to do this? I can send you more
>> details if you like.
>
> Sure, pls send more info on this.

  1. Add an 'int has_foreign_mappings' to mmu_context structure
  2. Ensure the field is initialised in init_new_context() (e.g.,
memset-zero the whole structure; already done on x86/64)
  3. Set the field in direct_remap_pfn_range()
  4. Check the field in _arch_exit_mmap() to avoid calling mm_unpin().

That's it. Just needs testing.

  -- Keir


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