Re: [Xen-devel] [PATCH v7.2 07/24] x86/mm: Introduce modify_xen_mappings()

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 11.04.16 at 19:46, <andrew.cooper3@xxxxxxxxxx> wrote:
> To simply change the permissions on existing Xen mappings.  The existing
> destroy_xen_mappings() is altered to support a change the PTE permissions.
> 
> A new destroy_xen_mappings() is introduced, as the special case of not passing
> _PAGE_PRESENT to modify_xen_mappings().
> 
> As cleanup (and an ideal functional test), the boot logic which remaps Xen's
> code and data with reduced permissions is altered to use
> modify_xen_mappings(), rather than map_pages_to_xen() passing the same mfn's
> back in.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
with one remark:

> -            /* If we are done with the L2E, check if it is now empty. */
> -            if ( (v != e) && (l1_table_offset(v) != 0) )
> +            /*
> +             * If we not destroying mappings, or are not done with the L2E,
> +             * skip the empty&free check.
> +             */
> +            if ( (nf & _PAGE_PRESENT) || ((v != e) && (l1_table_offset(v) != 
> 0)) )

I guess the missing "are" in the two instances of this comment
can be folded in while committing.

Jan


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