Il 17/10/2012 20:37, Jan Kiszka ha scritto: > On 2012-10-17 18:44, Paolo Bonzini wrote: >> 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), > > Unnecessary. Both models (KVM in-kernel and QEMU userspace) are > compatible - in the absence of bugs.
He wants to really switch it on the fly---not just migrate out and in---and for that you need to disable the KVM-specific devices. > But loading a KVM image into TCG lets non-trival guests lock up. Likely > due to differences in the CPU virtualization/emulation (MSRs...). Perhaps that can be mitigated by using an older machine model. Start with something simple like a pentium2 and work up from there... Paolo
