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Date: Tue, 06 Mar 2012 14:56:32 +0200
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Subject: Re: [Qemu-devel] [PATCH] target-i386: Mask NX bit from
 cpu_get_phys_page_debug result
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To: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Blue Swirl <blauwirbel@gmail.com>, Anthony Liguori <aliguori@us.ibm.com>, qemu-devel <qemu-devel@nongnu.org>

On 03/06/2012 02:23 PM, Jan Kiszka wrote:
> This was a long pending bug, now revealed by the assert in
> phys_page_find that stumbled over the large page index returned by
> cpu_get_phys_page_debug for NX-marked pages.
>
> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> ---
>
> Was easily triggerable by attaching gdb to the guest and doing some
> backtraces that reached into stack addresses.
>
>  target-i386/helper.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/target-i386/helper.c b/target-i386/helper.c
> index af6bba2..40fe407 100644
> --- a/target-i386/helper.c
> +++ b/target-i386/helper.c
> @@ -947,7 +947,7 @@ target_phys_addr_t cpu_get_phys_page_debug(CPUState *env, target_ulong addr)
>      }
>  
>      page_offset = (addr & TARGET_PAGE_MASK) & (page_size - 1);
> -    paddr = (pte & TARGET_PAGE_MASK) + page_offset;
> +    paddr = (pte & TARGET_PAGE_MASK & ~PG_NX_MASK) + page_offset;
>      return paddr;
>  }
>  

Should we not, in addition, mask the software available bits (53-62 IIRC)?

-- 
error compiling committee.c: too many arguments to function