Re: [Qemu-devel] [PATCH] qxl: use correct rom size for revision < 4

[Alon Levy]

> On 12/06/12 16:41, Alon Levy wrote:
> > RHBZ 869981
> > 
> > Before this patch revision < 4 (4 is the default) would result in a
> > wrong
> > qxl_rom size of 16384 instead of 8192 when building with
> > spice-protocol-0.12, due to the addition of fields in
> > the rom for client capabilities and monitors config that were added
> > between spice-protocol 0.10 and 0.12.
> > 
> > The solution is a bit involved, since I decided not to change
> > QXLRom
> > which is defined externally in spice-protocol. Instead for revision
> > < 4
> > we allocate 72 bytes for the QXLRom on the qxl_rom bar (bytes
> > [0,71])
> > and make sure no fields out of that range are accessed, via
> > checking of
> > the revision and nop-ing.
> 
> Ok, I see we tackle two issues here.
> 
> Number one is qxl accessing the new fields with revision being < 4.
> That needs fixing indeed.  But separate patch please.

Will do.

> 
> Number two is breaking migration due to the rom size change.  Can't
> we
> just get the rom below 8k again instead?  I think we can throw away a
> whole bunch of modes.  Each mode is four times in the list, for
> orientation = { 0, 1, 2, 3 }.  orientation is never ever used
> anywhere,
> looks like historic leftover or something planned which was never
> actually implemented.
> 
> So keeping orientation = 0 only and kick out everything else should
> give
> us plenty of room ...

That is indeed a better solution, but it does change functionality. I think it 
is correct but I'd like to get some other opinions - Uri, Arnon, Yonit, Soren - 
any problems with dropping these?

> 
> cheers,
>   Gerd
> 
>