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

[Tim Deegan <tim@xxxxxxx>]

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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