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

[Raghavendra K T]

On 12/08/2011 03:10 PM, Avi Kivity wrote:
> On 12/07/2011 06:46 PM, Raghavendra K T wrote:
> > On 12/07/2011 08:22 PM, Avi Kivity wrote:
> > > On 12/07/2011 03:39 PM, Marcelo Tosatti wrote:
> > > > > Also I think we can keep the kicked flag in vcpu->requests, no need
> > > > > for
> > > > > new storage.
> > > >
> > > > Was going to suggest it but it violates the currently organized
> > > > processing of entries at the beginning of vcpu_enter_guest.
> > > >
> > > > That is, this "kicked" flag is different enough from vcpu->requests
> > > > processing that a separate variable seems worthwhile (even more
> > > > different with convertion to MP_STATE at KVM_GET_MP_STATE).
> > >
> > > IMO, it's similar to KVM_REQ_EVENT (which can also cause mpstate to
> > > change due to apic re-evaluation).
> >
> > Ok, So what I understand is we have to either :
> > 1. retain current kick flag AS-IS but would have to make it migration
> > friendly. [I still have to get more familiar with migration side]
> > or
> > 2. introduce notion similar to KVM_REQ_PVLOCK_KICK(??) to be part of
> > vcpu->requests.
> >
> > So what would be better? Please let me know.
>
> IMO, KVM_REQ.

Ok, 'll continue in this direction. Hmm I think now the race condition 
should be kept in mind, pointed by Marcello.

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