Re: [Xen-devel] [PATCH V8 2/5] x86/hvm: pkeys, add pkeys support for guest_walk_tables

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 02.02.16 at 08:35, <huaitong.han@xxxxxxxxx> wrote:
> Protection keys define a new 4-bit protection key field(PKEY) in bits 62:59 
> of
> leaf entries of the page tables.
> 
> PKRU register defines 32 bits, there are 16 domains and 2 attribute bits per
> domain in pkru, for each i (0 â i â 15), PKRU[2i] is the access-disable bit 
> for
> protection key i (ADi); PKRU[2i+1] is the write-disable bit for protection 
> key
> i (WDi). PKEY is index to a defined domain.
> 
> A fault is considered as a PKU violation if all of the following conditions 
> are
> true:
> 1.CR4_PKE=1.
> 2.EFER_LMA=1.
> 3.Page is present with no reserved bit violations.
> 4.The access is not an instruction fetch.
> 5.The access is to a user page.
> 6.PKRU.AD=1
>     or The access is a data write and PKRU.WD=1
>                 and either CR0.WP=1 or it is a user access.
> 
> Signed-off-by: Huaitong Han <huaitong.han@xxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
albeit ...

> Changes in v8:
> *Abstract out _write_cr4.

... I'm not happy about the chose name and will try to remember
to change it to e.g. raw_write_cr4(). Names starting with an
underscore and a lower case letter are reserved to symbols
local to a given translation unit, which in my reading doesn't fit
with them getting placed in header files.

Jan

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