On Mi, 2015-04-01 at 22:55 +0800, John Hunter wrote:
Hi Gerd, I've read the patches about the virtio-gpu, it's a nice design. As far as I know, there are two other drivers used by qemu, CIRRUS and BOCHS. I have a question about the relationship of these three drivers, is that the virtio-gpu designed to replace the other two drivers? I mean are the CIRRUS and BOCHS going to be deprecated in the future?
qemu has a bunch of different virtual graphics cards, and these are the drivers for them. cirrus used to be the default gfx card until recently (qemu older then version 2.2). stdvga (bochs driver) is the current default. So expect them to be around for a while.
virtio-gpu will not replace them.
Actually, this is a problem by Martin Peres who is the GSoC xorg administor. My proposal is "Convert the BOCHS and CIRRUS drivers to atomic mode-setting".
Surely makes sense for bochs and you shouldn't find major blockers. Not sure this is a reasonable task size for gsoc given it took me only a few days to convert virtio-gpu to atomic modesetting. But maybe fine if you are new to drm kernel hacking and therefore the task includes learning alot new stuff.
I have my doubts it'll work out for cirrus though, due to the small amount of video memory it has (and other limitations, because we mimic hardware from the 90ies here). Current code is already swapping framebuffers in and out of video ram because of that. So atomic modesetting, page flip, running wayland on that beast all is going to be problematic I expect.
See also: https://www.kraxel.org/blog/2014/10/qemu-using-cirrus-considered-harmful/
HTH, Gerd