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

Kashyap Chamarthy kchamart at redhat.com
Mon Jan 31 15:21:36 UTC 2022

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.



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