On 14.06.2024 18:44, Demi Marie Obenour wrote: > On Fri, Jun 14, 2024 at 10:12:40AM +0200, Jan Beulich wrote: >> On 14.06.2024 09:21, Roger Pau Monné wrote: >>> I'm not sure it's possible to ensure that when using system RAM such >>> memory comes from the guest rather than the host, as it would likely >>> require some very intrusive hooks into the kernel logic, and >>> negotiation with the guest to allocate the requested amount of >>> memory and hand it over to dom0. If the maximum size of the buffer is >>> known in advance maybe dom0 can negotiate with the guest to allocate >>> such a region and grant it access to dom0 at driver attachment time. >> >> Besides the thought of transiently converting RAM to kind-of-MMIO, this >> makes me think of another possible option: Could Dom0 transfer ownership >> of the RAM that wants mapping in the guest (remotely resembling >> grant-transfer)? Would require the guest to have ballooned down enough >> first, of course. (In both cases it would certainly need working out how >> the conversion / transfer back could be made work safely and reasonably >> cleanly.) > > The kernel driver needs to be able to reclaim the memory at any time. > My understanding is that this is used to migrate memory between VRAM and > system RAM. It might also be used for other purposes.
Except: How would the kernel driver reclaim the memory when it's mapped by a DomU? Jan
