Hi, > virt-manager/libvirt seems to default to 9 MByte of Vram for cirrus, > so this would break a lot of setups.
It wouldn't. libvirt sticks that into the xml, but it doesn't set any qemu parameters. The libvirt parameter actually predates the qemu property for setting the size. > Looking at datasheets on the web seems to say the chips actually went > down to 1 MB or less. I have my doubts we emulate that correctly (register telling the guest how much memory is actually there etc.). Also it is pretty much useless these days, even the 4MB imply serious constrains when FullHD displays are commonplace. Newer cirrus drivers such as the kernel's drm driver are specifically written to qemu's cirrus cards, I have my doubs that they are prepared to handle 1MB cirrus cards correctly. Bottom line: Allowing less than 4MB is asking for trouble for no good reason ;) cheers, Gerd
