Re: [PATCH RFC 1/2] arm/kvm: enable MTE if available

[Cornelia Huck <cohuck@redhat.com>]

On Wed, Jun 29 2022, Eric Auger <eauger@redhat.com> wrote:

> Hi Connie,
>
> On 6/14/22 10:40, Cornelia Huck wrote:
>> On Fri, Jun 10 2022, Eric Auger <eauger@redhat.com> wrote:
>> 
>>> Hi Connie,
>>> On 5/12/22 15:11, Cornelia Huck wrote:
>>>> We need to disable migration, as we do not yet have a way to migrate
>>>> the tags as well.
>>>
>>> This patch does much more than adding a migration blocker ;-) you may
>>> describe the new cpu option and how it works.
>> 
>> I admit this is a bit terse ;) The idea is to control mte at the cpu
>> level directly (and not indirectly via tag memory at the machine
>> level). I.e. the user gets whatever is available given the constraints
>> (host support etc.) if they don't specify anything, and they can
>> explicitly turn it off/on.
>
> Could the OnOffAuto property value be helpful?

I completely forgot that this exists; I hacked up something (still
untested), and it seems to be able to do what I want.

I'll post it after I've verified that it actually works :)

>> The big elefant in the room is how migration will end up
>> working... after reading the disscussions in
>> https://lore.kernel.org/all/CAJc+Z1FZxSYB_zJit4+0uTR-88VqQL+-01XNMSEfua-dXDy6Wg@mail.gmail.com/
>> I don't think it will be as "easy" as I thought, and we probably require
>> some further fiddling on the kernel side.
> Yes maybe the MTE migration process shall be documented and discussed
> separately on the ML? Is Haibu Xu's address bouncing?

Yes, that address is bouncing...

I've piggybacked onto a recent kvm discussion in
https://lore.kernel.org/all/875ykmcd8q.fsf@redhat.com/ -- I guess there
had not been any change for migration in the meantime, we need to find a
way to tie page data + metadata together.