Re: [PATCH 2/3] KVM: MMU: Introduce a helper to read guest pte

[Avi Kivity <avi@redhat.com>]

On 04/20/2011 02:06 PM, Roedel, Joerg wrote:
> On Wed, Apr 20, 2011 at 06:05:08AM -0400, Avi Kivity wrote:
> >  On 04/20/2011 12:35 PM, Roedel, Joerg wrote:
>
> >  >  This patch seems only to introduce another wrapper around
> >  >  kvm_read_guest_page_mmu(), so I don't see a problem in this patch.
> >
> >  By patch 3, ptep_user will be computed in this function and no longer
> >  available for setting the accessed bit later on.
> >
> >  >  The kvm_read_guest_page_mmu takes care whether it gets a l1-gfn or
> >  >  l2-gfn (by calling mmu->translate_gpa).
> >
> >  But cmpxchg_gpte() does not.
>
> You are right, cmpxchg_gpte needs to handle this too. But the bug is not
> introduced with this patch-set it was there before.

Correct.  The reason I don't want the helper, is so we can use ptep_user 
in both places (not for efficiency, just to make sure it's exactly the 
same value).

> The cmpxchg_gpte function treats all table_gfns as l1-gfns. I'll send a
> fix soon.

Thanks.

-- 
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