[PATCH 1/3] powerpc/kvm: simplify the entering logic for secondary thread

[Liu ping fan]

On Wed, Nov 6, 2013 at 1:01 PM, Paul Mackerras <paulus at samba.org> wrote:
> On Tue, Nov 05, 2013 at 03:42:42PM +0800, Liu Ping Fan wrote:
>> After the primary vcpu changes vcore_state to VCORE_RUNNING, there is
>> very little chance to schedule to secondary vcpu. So if we change the
>
> Why do you say there is very little chance to run the secondary vcpu?
>
>> code sequence around set vcore_state to VCORE_RUNNING and disable
>> preemption, we lost little. But we simplify the entering logi, based on
>> the fact that if primary vcpu runs, the secondary vcpu can not be scheduled.
>
> If a vcpu does a hypercall or something else that requires the host
> (kernel or userspace) to do something, that can happen in the context
> of the vcpu task for that vcpu.  That vcpu task can run on another
> core (unless it has been pinned).  When it is finished we would like
> the vcpu to continue executing in the guest as soon as possible.  The
> code that you remove in this patch enables that to happen without
> having to wait until the other threads exit the guest.  So I don't
> think it is a good idea to remove this code.
>
Yes, you are right.

Thanks and regards,
Pingfan


> Regards,
> Paul.