On 23.11.21 18:00, Jason Gunthorpe wrote: > On Tue, Nov 23, 2021 at 03:44:03PM +0100, David Hildenbrand wrote: >> On 23.11.21 15:07, Jason Gunthorpe wrote: >>> On Tue, Nov 23, 2021 at 02:39:19PM +0100, David Hildenbrand wrote: >>>>> >>>>>> 2) Could be provide a mmu variant to ordinary users that's just good >>>>>> enough but maybe not as fast as what we have today? And limit >>>>>> FOLL_LONGTERM to special, privileged users? >>>>> >>>>> rdma has never been privileged >>>> >>>> Feel free to correct me if I'm wrong: it requires special networking >>>> hardware and the admin/kernel has to prepare the system in a way such >>>> that it can be used. >>> >>> Not really, plug in the right PCI card and it works >> >> Naive me would have assumed that the right modules have to be loaded >> (and not blacklisted), that there has to be an rdma service installed >> and running, that the NIC has to be configured in some way, and that >> there is some kind of access control which user can actually use which >> NIC. > > Not really, we've worked hard that it works as well as any other HW > device. Plug it in and it works. > > There is no systemd service, or special mandatory configuration, for > instance. > >> For example, I would have assume from inside a container it usually >> wouldn't just work. > > Nope, RDMA follows the net namespaces of its ethernet port, so it just > works in containers too. > >> believe what you say and I trust your experience :) So could as well be >> that on such a "special" (or not so special) systems there should be a >> way to restrict it to privileged users only. > > At this point RDMA is about as "special" as people running large > ZONE_MOVABLE systems, and the two are going to start colliding > heavily. The RDMA VFIO migration driver should be merged soon which > makes VMs using this stuff finally practical. Sounds like fun. At least we documented it already ;) https://www.kernel.org/doc/html/latest/admin-guide/mm/memory-hotplug.html#zone-movable-sizing-considerations -- Thanks, David / dhildenb
