Re: [PART1 RFC 5/9] svm: Add VMEXIT handlers for AVIC

[Suravee Suthikulpanit]

Hi,

On 2/19/16 00:18, Paolo Bonzini wrote:
> On 18/02/2016 17:27, Radim KrÄmÃÅ wrote:
> > 2016-02-18 16:53+0100, Paolo Bonzini:
> > > Patch 9 is okay, but it is also necessary to clear IsRunning in
> > > kvm_arch_vcpu_blocking and set it in kvm_arch_vcpu_unblocking.  In
> > > addition, vcpu_put/vcpu_load should not modify IsRunning between
> > > kvm_arch_vcpu_blocking and kvm_arch_vcpu_unblocking.  Do you agree?
> >
> > Yes.
> >
> > I think we don't need to clear IsRunning on preemption, which would
> > simplify the protection.  (I haven't thought much about userspace exit,
> > so maybe we could skip that one as well, but we don't need to now.)
> >
> > The reason for that is that KVM knows that the VCPU was scheduled out,
> > so it couldn't do much in the AVIC VMEXIT.
> > (KVM could force scheduler to pritioritize the VCPU, but our kick
> >   doesn't do that now and it seems like a bad idea.)
> >
> > Does it seem reasonable?
>
> Yes, and in fact it wouldn't need to clear and set IsRunning on
> vcpu_put/vcpu_load; only on vcpu_blocking/vcpu_unblocking.
>
> The IsRunning flag is more of a IsNotHalted flag, in the end.
>
> Paolo

Good point. I have made the change by introducing new function pointer, 
kvm_x86_ops.vcpu_blocking() and kvm_x86_ops.vcpu_unblocking(). Then 
provides the hook to set/unset the IsRunningBit here. Also, I no longer 
set the bit in the vcpu_load/vcpu_put.

If this is okay. I'll send out V2 soon.

Thanks,
Suravee