Re: [PATCH RFC 1/2] kvm: Handle undercommitted guest case in PLEhandler

[Raghavendra K T]

On 10/04/2012 12:59 PM, Gleb Natapov wrote:
> On Wed, Oct 03, 2012 at 04:56:57PM +0200, Avi Kivity wrote:
> > On 10/03/2012 04:17 PM, Raghavendra K T wrote:
> > > * Avi Kivity <avi@xxxxxxxxxx> [2012-09-30 13:13:09]:
> > >
> > > > On 09/30/2012 01:07 PM, Gleb Natapov wrote:
> > > > > On Sun, Sep 30, 2012 at 10:18:17AM +0200, Avi Kivity wrote:
> > > > > > On 09/28/2012 08:16 AM, Raghavendra K T wrote:
> > > > > > > >      +struct pv_sched_info {
> > > > > > > >      +       unsigned long   sched_bitmap;
> > > > > > >
> > > > > > > Thinking, whether we need something similar to cpumask here?
> > > > > > > Only thing is we are representing guest (v)cpumask.
> > > > > >
> > > > > > DECLARE_BITMAP(sched_bitmap, KVM_MAX_VCPUS)
> > > > > vcpu_id can be greater than KVM_MAX_VCPUS.
> > > >
> > > > Use the index into the vcpu table as the bitmap index then.  In fact
> > > > it's better because then the lookup to get the vcpu pointer is trivial.
> > >
> > > Did you mean, while setting the bitmap,
> > >
> > > we should do
> > > for (i = 1..n)
> > > if (kvm->vcpus[i] == vcpu) set ith position in bitmap?
> >
> > You can store i in the vcpu itself:
> >
> >    set_bit(vcpu->index, &kvm->preempted);
> This will make the fact that vcpus are stored in an array into API
> instead of implementation detail :( There were patches for vcpu
> destruction that changed the array to rculist. Well, it will be still
> possible to make the array rcu protected and copy it every time vcpu is
> deleted/added I guess.

If IUC, summary is, we are going with
- Let vcpu array be rcu protected.
- we use index inside vcpu and should be updated when a vcpu is
added/deleted.

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