Il 17/10/2012 18:37, Clemens Kolbitsch ha scritto: > Guys, > > I know this is question might seem a bit odd, but I'm curious: > > Has anyone ever tried to write code to disable KVM on the fly / is it > at all possible? I have a situation where I need to use TCG for > certain parts of the code, but would love to have acceleration for > everything else. My idea was to pause the VM, then use the > snapshotting mechanism to dump the state, and then to resume the > snapshot, but writing the KVM state into the non-KVM structures.
As a start, you can try using "migrate exec:cat>foo.save" with a KVM machine and "-incoming 'exec:cat foo.save'" with a TCG machine. The main problem should be that TCG doesn't implement kvmclock. If you disable the KVM interrupt controller and timer (which is just an implementation detail, not a hardware difference), the differences between KVM and TCG are just that KVM doesn't initialize some TCG-only data structure, and that KVM uses many CPU threads; TCG uses one that goes through CPUs round-robin. The CPU threads of course execute different code. So no, in theory there is nothing that prevents this from working in principle, except for kvmclock. Paolo > I know nothing of that sort is implemented at this point. Leaving > aside the issue of certain CPUID instructions suddenly returning > different results, are there obvious problems even trying to go down > that road? > > Would love to hear some thoughts on this - don't hesitate to tell me > "that's stupid and impossible because XYZ" (assuming you also fill in > the blanks ;) ) > > Thanks! > Clemens >
