Re: [PATCHv7 02/14] mm: Add support for unaccepted memory

David Hildenbrand
2022-07-25T12:39:02Z

On 25.07.22 14:23, Borislav Petkov wrote:
> On Fri, Jul 22, 2022 at 12:30:36PM -0700, Dave Hansen wrote:
>> Sure does... *Something* has to manage the cache coherency so that old
>> physical aliases of the converted memory don't write back and clobber
>> new data. But, maybe the hardware is doing that now.
>
> Let's hope.
>
>> Yeah, that two-tier system is the way it's happening today from what
>> I understand. This whole conversation is about how to handle the >4GB
>> memory.
>
> Would it be possible to pre-accept a bunch of mem - think "pre-fault" -
> from userspace?
>
> I.e., I'm thinking some huge process is going to start in the VM, VM
> userspace goes and causes a chunk of memory to be pre-accepted and then
> the process starts and runs more-or-less smoothly as the majority of its
> memory has already been "prepared".
>
> Or does that not make any sense from mm perspective?
>

The less core-MM code to handle unaccepted memory the better. Meaning,
that any kind of additional pre-acceptance (in addition to what we have
here) needs good justification.

--
Thanks,

David / dhildenb