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

[Gerd Hoffmann]

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.

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 ...

cheers,
  Gerd