Re: [Qemu-devel] [PATCH v1 4/5] kvm/x86: Hyper-V VMBus hypercall userspace exit

[Pavel Fedin]

 Hello!

> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -3359,6 +3359,14 @@ Hyper-V SynIC state change. Notification is used to 
> remap SynIC
>  event/message pages and to enable/disable SynIC messages/events processing
>  in userspace.
> 
> +             /* KVM_EXIT_HYPERV_HCALL */
> +             struct {
> +                     __u64 input;
> +                     __u64 params[2];
> +                     __u64 result;
> +             } hv_hcall;
> +Indicates that the VCPU exits into userspace to process some guest
> +Hyper-V hypercalls.

 Why introducing this? We already have KVM_EXIT_HYPERCALL, which is exactly the 
same. AFAIK it's not used at the moment.
 Additionally, in theory we could have hypercalls handled in userspace for 
something else except HyperV. And not only for x86.

Kind regards,
Pavel Fedin
Senior Engineer
Samsung Electronics Research center Russia