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

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

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

 -- Keir

On 18/10/07 02:11, "John Levon" <levon@xxxxxxxxxxxxxxxxx> wrote:

> 
> I think the below fix is correct, though as I'm far from comfortable
> with this code I'd like some comments first...
> 
> 'val' is the unmodified pte value written by the guest. We need to use
> nl1e instead, which has done the needed PAGE_GLOBAL etc. modifications.
> 
> cheers,
> john
> 
> # HG changeset patch
> # User john.levon@xxxxxxx
> # Date 1192664022 25200
> # Node ID d2eed7e51be31880f04033d1241861602d3628bb
> # Parent  a6b52e05bcd026a7d378fff130b90d6eda62209a
> 
> diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
> --- a/xen/arch/x86/mm.c
> +++ b/xen/arch/x86/mm.c
> @@ -3204,7 +3204,7 @@ static int ptwr_emulated_update(
>          if ( shadow_mode_enabled(d) )
>              shadow_lock(d);
>          ol1e = l1e_from_intpte(old);
> -        if ( cmpxchg((intpte_t *)pl1e, old, val) != old )
> +        if ( cmpxchg((intpte_t *)pl1e, old, l1e_get_intpte(nl1e)) != old )
>          {
>              if ( shadow_mode_enabled(d) )
>                  shadow_unlock(d);
> 
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