Re: [Xen-devel] [PATCH RFC V3 2/4] kvm hypervisor : Add a hypercall to KVM hypervisor to support pv-ticketlocks

[Raghavendra K T <raghukt@xxxxxxxxxxxxxxxxxx>]

On 12/07/2011 06:03 PM, Marcelo Tosatti wrote:
> On Wed, Dec 07, 2011 at 05:24:59PM +0530, Raghavendra K T wrote:
> > On 12/07/2011 04:18 PM, Marcelo Tosatti wrote:
> > Yes you are right. It was potentially racy and it was harmful too!.
> > I had observed that it was stalling the CPU before I introduced
> > kicked flag.
> >
> > But now,
> >
> > vcpu->kicked = 1  ==>  kvm_make_request(KVM_REQ_UNHALT, vcpu); ==>
> Ok, please use a more descriptive name, such as "pvlock_kicked" or
> something.
Yes, pvlock_kicked seems good. 'll use same unless something else
flashes.

> > __vcpu_run() ==>  kvm_check_request(KVM_REQ_UNHALT, vcpu) ==>
> >
> > vcpuN->mp_state = KVM_MP_STATE_RUNNABLE; so eventually we will end up
> > in RUNNABLE.
> >
> > Also Avi pointed that, logically kvm_arch_vcpu_ioctl_set_mpstate should
> > be called only in vcpu thread, so after further debugging, I noticed
> > that,  setting vcpuN->mp_state = KVM_MP_STATE_RUNNABLE; is not
> > necessary.
> > I 'll remove that in the next patch. Thanks for pointing.
> In fact you don't need kvm_arch_vcpu_ioctl_set_mpstate either, only the
> new "kicked" flag.
True indeed, I meant the same.


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