Re: [PATCH] KVM breaks CPU hotplug

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

Li, Shaohua wrote:
> How about take cpu hotplug lock for kvm_vm_ioctl and kvm_vcpu_ioctl?
>
>   

That will serialize calls to these functions, and we want parallel 
execution of kvm_vcpu_ioctl().  We could make it a reader-writer lock, 
but...

I think that adding a

    raw_notifier_call_chain(&cpu_chain, CPU_DYING, NULL);

in take_cpu_down() solve the problem.  The semantics of that would be 
that the chain is executed on the dying cpu, without being allowed to 
fail, and requiring atomic execution.  I don't know whether that would 
acceptable to the cpu hotplug maintainers.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.


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