>-----Original Message----- >From: Avi Kivity [mailto:[EMAIL PROTECTED] >Sent: Monday, March 26, 2007 6:58 PM >To: Li, Shaohua >Cc: kvm-devel; Andrew Morton >Subject: Re: [PATCH] KVM breaks CPU hotplug > >Avi Kivity wrote: >> Shaohua Li wrote: >>> When testing CPU hotplug, I found cpu can't be onlined with kvm enabled >>> sometimes. The reason is smp_call_function_single is a nop if the thread >>> is running on the target cpu. I think CPU_ONLINE case doesn't require >>> the fix as the online CPU isn't plugged into sheduler yet. >>> >>> >> >> I think this is not enough, because: >> >> - this path is preemptible code, so the test (this_cpu == cpu) can run >> one on cpu and execute later code on another >>> + this_cpu = get_cpu(); > >... > >>> + put_cpu(); > >Sorry, I see you handled that. But the other argument (scheduling vcpus >later on same cpu) still holds, I think. How about take cpu hotplug lock for kvm_vm_ioctl and kvm_vcpu_ioctl?
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