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

[Paolo Bonzini]

On 18/02/2016 15:18, Radim KrÄmÃÅ wrote:
> KVM just has to make sure that targeted VCPUs notice the interrupt,
> which means to kick (wake up) VCPUs that don't have IsRunning set.
> There is no need to do anything with running VCPUs, because they
>  - are in guest mode and noticed the doorbell
>  - are in host mode, where they will
>    1) VMRUN as fast as they can because the VCPU didn't want to halt
>       (and IRR is handled on VMRUN)
>    2) check IRR after unsetting IsRunning and goto (1) if there are
>       pending interrupts.  (RFC doesn't do this, which is another bug)

This is not necessary.  IsRunning is only cleared at vcpu_put time.  The
next KVM_RUN will look at IRR (kvm_arch_vcpu_runnable), if necessary set
the mp_state to KVM_MP_STATE_RUNNABLE, and do the VMRUN.

But I agree that this is what Suravee is missing.

> It's still possible that we misunderstood the spec.  Does AVIC handle
> IPIs differently?

I don't think we misunderstood it.  Well, I did, but that's fixed now. :)

Paolo