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Re: [Xen-devel] bug in PT write emulation

To: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] bug in PT write emulation
From: John Levon <levon@xxxxxxxxxxxxxxxxx>
Date: Thu, 18 Oct 2007 11:23:43 +0100
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On Thu, Oct 18, 2007 at 08:05:48AM +0100, Keir Fraser wrote:

> You could be right, although what version of Xen is that code snippet from?
> Xen 3.1 and Xen unstable both look quite different.

3.0.4. I just checked xen-unstable (sorry) - it has the same bug:

3377     adjust_guest_l1e(nl1e, d);
3378
...
3382     if ( do_cmpxchg )
3383     {
...
3388         okay = paging_cmpxchg_guest_entry(v, &l1e_get_intpte(*pl1e),
3389                                           &t, val, _mfn(mfn));

"val" not "nl1e"

I suspect this is hurting performance for us.

cheers,
john

PS slightly related note - is _PAGE_GUEST_KERNEL part of the ABI?

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