The vram attribute was introduced to set the video memory but it is
usable only for few hypervisors excluding QEMU/KVM and the old XEN
driver. Only in case of QEMU the vram was used for QXL.
This patch updates the documentation to reflect current code in libvirt
and also changes the cases when we will set the default vram attribute.
It also fixes existing strange default value for VGA devices 9MB to 16MB
because the video ram should be rounded to power of two.
The change of default value could affect migrations but I found out that
QEMU always round the video ram to power of two internally so it's safe
to change the default value to the next closest power of two and also
silently correct every domain XML definition. And it's also safe because
we don't pass the value to QEMU.
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1076098
Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
Adds a "ram" attribute globally to the video.model element, that changes
the resulting qemu command line only if video.type == "qxl".
<video>
<model type='qxl' ram='65536' vram='65536' heads='1'/>
</video>
That attribute gets a default value of 64*1024. The schema is unchanged
for other video element types.
The resulting qemu command line change is the addition of
-global qxl-vga.ram_size=<ram>*1024
or
-global qxl.ram_size=<ram>*1024
For the main and secondary qxl devices respectively.
The default for the qxl ram bar is 64*1024 kilobytes (the same as the
default qxl vram bar size).
