Re: [patch 2/5] KVM: reintroduce guest mode bit and unify remote request code

Marcelo Tosatti
2009-08-27T12:58:50Z

On Thu, Aug 27, 2009 at 11:15:23AM +0300, Avi Kivity wrote:
> On 08/27/2009 04:20 AM, Marcelo Tosatti wrote:
>> Split KVM_REQ_KICKED in two bits: KVM_VCPU_KICKED, to indicate
>> whether a vcpu has been IPI'ed, and KVM_VCPU_GUEST_MODE, in a separate
>> vcpu_state variable.
>>
>> Unify remote requests with kvm_vcpu_kick.
>>
>> Synchronous requests wait on KVM_VCPU_GUEST_MODE, via wait_on_bit/wake_up_bit.
>>
>>
>
> I did miss guest_mode.
>
>> + unsigned long vcpu_state;
>>
>
> Why not bool guest_mode? Saves two atomics per exit.

It must be atomic since GUEST_MODE / VCPU_KICKED bits are manipulated by
multiple CPU's.