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

[Julien Grall <julien.grall@xxxxxxx>]

Hi Andrew,

On 18/05/17 16:02, Andrew Cooper wrote:
> 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".
> Done.
>
> > >  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>

Cheers,

--
Julien Grall

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