Re: [PATCH v2] docs: expand firmware descriptor to allow flash without NVRAM

On Mon, Jan 31, 2022 at 02:36:46PM +0000, Daniel P. Berrangé wrote: > On Mon, Jan 31, 2022 at 03:00:33PM +0100, Kashyap Chamarthy wrote: > > On Mon, Jan 31, 2022 at 12:55:09PM +0000, Daniel P. Berrangé wrote: [...] > > I briefly wondered if in this "combined" mode whether the no. of > > duplicate copies can ever fill up the storage. I doubt that, as the > > combined size of _VARS + _CODE is just about 2MB. So it only starts > > mattering if you're running tens of thousands of guests. > > When guest root / data disk sizes are measured in 100's of MB, or > GBs, I struggle to get worried about even a 16 MB OVMF blob being > copied per guest. Heh, fair enough. > The firmware can be provided in qcow2 format too, so if really > concerned, just create a qcow2 file with a backing store pointing > to the readonly master, so you're only paying the price of the > delta for any guest VARs writes. That's more efficient than what > we do today with copying the separate raw format VARS.fd file. That's nice, I didn't know the qcow2 possibility in this context. For some reason I assumed the file format always has to be raw here. Your qcow2 point above should be documented, if it isn't already. Although I don't know the right place for it.