On 10/20/15 11:44 PM, Paolo Bonzini wrote:
On 20/10/2015 11:57, Yacine wrote:
vcpu_load; start cr3 trapping; vcpu_put
it worked correctly (in my logs I see that vcpu.cpu become equal to "cpu =
raw_smp_processor_id();") but the VM blocks for a lot of time due to mutex
in vcpu_load (up to serveral seconds and sometimes minutes !)
Right, that's because while the CPU is running the mutex is taken. If
the VCPU doesn't exit, the mutex is held.
I replaced vcpu_load with kvm_sched_in, now everything works perfectly and
the VM doesn't block at all (logs here: http://pastebin.com/h5XNNMcb).
So, what I want to know is: what is the difference between vcpu_load and
kvm_sched_in ? both of this functions call kvm_arch_vcpu_loadbut the latter
one does it without doing a mutex
kvm_sched_out and kvm_sched_in are part of KVM's preemption hooks. The
hooks are registered only between vcpu_load and vcpu_put, therefore they
know that the mutex is taken. The sequence will go like this:
vcpu_load
kvm_sched_out
kvm_sched_in
kvm_sched_out
kvm_sched_in
...
vcpu_put
If this should be:
vcpu_load
kvm_sched_in
kvm_sched_out
kvm_sched_in
kvm_sched_out
...
vcpu_put
Regards,
Wanpeng Li
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