Re: [Xen-devel] [PATCH v2] Livepatch for ARM 64 and 32.

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 31/08/16 16:09, Julien Grall wrote:
>
>
> On 31/08/16 16:06, Konrad Rzeszutek Wilk wrote:
>> On Wed, Aug 31, 2016 at 03:49:55PM +0100, Julien Grall wrote:
>>> On 25/08/16 14:37, Konrad Rzeszutek Wilk wrote:
>>>> Hey!
>>>
>>> Hi Konrad,
>>>
>>>> Since v1 (and RFC):
>>>> [https://lists.xen.org/archives/html/xen-devel/2016-08/msg01835.html]
>>>>  - Acted on most all comments.
>>>>  - Added ARM32 support.
>>>>
>>>> The patches are based on: [PATCH v4] Livepatch fixes and features
>>>> for v4.8.
>>>> (https://lists.xen.org/archives/html/xen-devel/2016-08/msg02705.html)
>>>>
>>>> And the git tree is:
>>>>  git://xenbits.xen.org/people/konradwilk/xen.git livepatch.v4.8.v4
>>>>
>>>> There are two outstanding questions that should be addressed at
>>>> some point:
>>>>  -  #16 "livepatch: tests: Make them compile under ARM64"
>>>>     We chatted about adding a specific CPU bit (LIVEPATCH) so that
>>>> alternative
>>>>     code always gets exercised. This being for both x86 and ARM.
>>>> But this has
>>>>     a side effect that it gets exposed to the toolstack and can
>>>> also be
>>>>     exposed to the guests. I think it is better if we do not do that
>>>>     so left it to be enabled based on the most common errata (or
>>>> feature
>>>>     on x86).
>>>
>>> There is no common errata on ARM. I spoke with Andrew which
>>> mentioned that
>>> on x86 they have architectural xen feature bits which are not
>>> exposed to the
>>> toolstack/guest.
>>>
>>> Furthermore, I think it would be unwise to let the toolstack aware
>>> of some
>>> errata and possibly setting/clearing them. So adding a specific
>>> feature bit
>>> is fine by me.
>>
>> So you are thinking of exposing this 'xen feature bits' that Andrew
>> mention
>> to be on ARM as well.
>
> I only chat with Andrew about it and I have not looked at the code, so
> I can't tell how it is on x86. I was just thinking to add LIVEPATCH
> bit in cpufeature.h for now and be worry later when cpufeature will be
> exposed to the toolstack for ARM.

Sorry - I have forgotten what exactly the purpose of this bit needs to
be, and therefore which bit of x86 I point you at.

~Andrew

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel