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Re: [Xen-devel] [PATCH v2 for-4.9] x86/pagewalk: Fix determination of Protection Key access rights

Hi Andrew,

On 18/05/17 16:02, Andrew Cooper wrote:
On 18/05/17 15:31, Tim Deegan wrote:

At 15:02 +0100 on 18 May (1495119734), Andrew Cooper wrote:
 * When fabricating gl1e's from superpages, propagate the protection key as
   well, so the protection key logic sees the real key as opposed to 0.

 * Experimentally, the protection key checks are performed ahead of the other
   access rights.  In particular, accesses which fail both protection key and
   regular permission checks yield PFEC_prot_key in the resulting pagefault.

 * Protection keys apply to all user mode data accesses, including accesses
   from supervisor code.
I think this would be clearer as "all data accesses to user-mode addresses".


 PKRU WD applies to any data write, not just to
   mapping which are writable.  However, a supervisor access without CR0.WP
   bypasses any protection from protection keys.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Reviewed-by: Tim Deegan <tim@xxxxxxx>

Release-acked-by: Julien Grall <julien.grall@xxxxxxx>


Julien Grall

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