> Subject: Re: [Qemu-devel] about the patch kvmclock Ensure proper env->tsc > value for kvmclock_current_nsec calculation > > > Thanks for your reply, I have read the thread in your email, what's the > mean of 'switching from old to new disk', could give a detail description? > > The test case was like that (using libvirt): > > 1. Get VM running (linux, using kvmclock), 2. Use blockcopy to copy disk data > from one location to another, 3. Issue blockjob --pivot (to finish mirroring) > > From what I remember, at point 3, VM is momentarily paused and resumed, > so kvm state change handler is called twice. Without this patch, the VM > hanged because its time goes backwards (or qemu crashed if assertion was > not compiled out). > > -- > mg
So, the problem is cause by stop_vm(RUN_STATE_PAUSED), in this case the env->tsc is not updated, which lead to the issue. Is that right? If the cpu_clean_all_dirty() is needed just for the APIC status reason, I think we can do the cpu_synchronize_all_states() in do_vm_stop and after vm_state_notify() when the RUN_STATE_PAUSED is hit, at this point all the device models is stopped, there is no outdated APIC status. I want to write a patch to fix this issue in another way, could help to verify it in you environment, very appreciate if you could. Thanks. Liang
