Re: [Xen-devel] [PATCH 25/27] xen/arm: mm: Embed permission in the flags

[Andre Przywara <andre.przywara@xxxxxxx>]

Hi,

On 23/08/17 15:26, Julien Grall wrote:
> On 08/23/2017 03:08 PM, Andre Przywara wrote:
>> Hi,
> 
> Hi,
> 
>> On 14/08/17 15:24, Julien Grall wrote:
>>> Currently, it is not possible to specify the permission of a new
>>> mapping. It would be necessary to use the function modify_xen_mappings
>>> with a different set of flags.
>>>

Just saw that I forgot the typos here:

>>> Add introduce a couple of new flags for the permissions (Non-eXecutable,

Either "add" or "introduce", I guess.

>>> Read-Only) and also provides define that combine the memory attribute
>>> and permission for common combination.

Somehow the plural/singular is messed up here, I needed to read that
sentence multiple times.

>>
>> If I haven't been lost in the definitions, this now adds "not
>> executable" to the existing definitions, which seems to make sense, but
>> is a change that might trigger regressions (especially for
>> PAGE_HYPERVISOR). So I wonder if that should be mentioned in the commit
>> message then?
> 
> It will not trigger regression because mfn_to_xen_entry is setting xn to
> 1 by default. So all the mapping will be execute never when using
> PAGE_HYPERVISOR.

Ah right, I missed that. Might still be worth to mention in the commit
message, as this isn't obvious from just that patch.

Cheers,
Andre.

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