Re: [PATCH v1 07/17] migration/rdma: Use ram_block_discard_set_broken()

David Hildenbrand
2020-05-15T14:09:52Z

On 15.05.20 14:45, Dr. David Alan Gilbert wrote:
> * David Hildenbrand (david@redhat.com) wrote:
>> RDMA will pin all guest memory (as documented in docs/rdma.txt). We want
>> to mark RAM block discards to be broken - however, to keep it simple
>> use ram_block_discard_is_required() instead of inhibiting.
>
> Should this be dependent on whether rdma->pin_all is set?
> Even with !pin_all some will be pinned at any given time
> (when it's registered with the rdma stack).

Do you know how much memory this is? Is such memory only temporarily pinned?

At least with special-cases of vfio, it's acceptable if some memory is
temporarily pinned - we assume it's only the working set of the driver,
which guests will not inflate as long as they don't want to shoot
themselves in the foot.

This here sounds like the guest does not know the pinned memory is
special, right?

--
Thanks,

David / dhildenb