On 08/20/2013 06:39 PM, Paolo Bonzini wrote: > Il 20/08/2013 03:36, Alexey Kardashevskiy ha scritto: >> Hm. Here we might have a problem like this is we decide to migrate from >> QEMU with this patch running on modern kernel to QEMU without this patch >> running on old kernel - for this we might want to be able to disable >> "multi-tce" via machine options on newer kernels. Do we care enough to add >> such a parameter or we just disable migration and that's it? > > Upstream doesn't support migration to older QEMU.
Hm. That makes things simpler. Then I do not understand why we need migration protocol versions as QEMU version in stronger version for migration. Ah, offtopic. >> This SandyBridge,enforce - what if the destination host running on old >> kernel was run without this option - will the migration fail? > > The destination machine will not even start. > >>> But in this case, you do not need this because the hypercall works if >>> emulated by QEMU. I like Alex's solution of making it universally >>> available in the dtb. >> >> The solution would be good if we did not already have H_PUT_TCE accelerated >> for emulated devices in the host kernel but we do have it. > > The question is also whether you consider pSeries support complete > enough to be production ready---and until you have versioned machine > types I would say you don't. > > If you still consider it somewhat experimental, I would do as Alex said: > make newer QEMU on older KVM as slower, and that's it. Sorry if I miss anything, but is not it what the patch already does? :) If so, I'll repost this patch + traces rework tomorrow or so. -- Alexey
