Re: [Xen-devel] [PATCH V3] x86/HVM: Introduce struct hvm_pi_ops

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 12.01.17 at 05:47, <suravee.suthikulpanit@xxxxxxx> wrote:
> --- a/xen/include/asm-x86/hvm/domain.h
> +++ b/xen/include/asm-x86/hvm/domain.h
> @@ -72,6 +72,38 @@ struct hvm_ioreq_server {
>      bool_t                 bufioreq_atomic;
>  };
>  
> +/*
> + * This structure defines function hooks to support hardware-assisted
> + * virtual interrupt delivery to guest. (e.g. VMX PI and SVM AVIC).
> + *
> + * The way we implement this now is by looking at what needs to happen on
> + * the following runstate transitions:
> + *
> + * A: runnable -> running  : switch_to
> + * B: running  -> runnable : switch_from

I don't think this is accurate - switch_from may be used when
transitioning to states other than runnable. Both hooks really
are context switch rather than run state related afaict.

> + * C: running  -> blocked  : vcpu_block
> + * D: blocked  -> runnable : do_resume

This one is, I think, similarly not so much run state related, but
instead used when a vCPU is about to enter guest context again.
The descriptions following this are more accurate. I note that
you've cloned this from the original, VMX specific description, but
I wonder whether that wouldn't better be corrected in this regard
at once. Otoh you're not making things worse, so if others are
in favor of it going in as is, I'd be fine too.

Other than that I'm fine with the patch, albeit I'd like the VMX
maintainers to specifically take a close look at the new placement
of the VMX specific comment.

Jan


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