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

On 18/05/17 15:31, Tim Deegan wrote:
> Hi,
> 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>



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