[PATCH 3/5] arm/arm64: KVM: Clarify KVM_ARM_VCPU_INIT ABI

[Peter Maydell]

On 27 November 2014 at 18:40, Christoffer Dall
<christoffer.dall at linaro.org> wrote:
> It is not clear that this ioctl can be called multiple times for a given
> vcpu.  Userspace already does this, so clarify the ABI.
>
> Signed-off-by: Christoffer Dall <christoffer.dall at linaro.org>
> ---
>  Documentation/virtual/kvm/api.txt | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index bb82a90..fc12b4f 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -2453,6 +2453,9 @@ return ENOEXEC for that vcpu.
>  Note that because some registers reflect machine topology, all vcpus
>  should be created before this ioctl is invoked.
>
> +Userspace can call this function multiple times for a given VCPU, which will
> +reset the VCPU to its initial states.

How about being a little bit more explicit here with something like:

"Userspace can call this function multiple times for a given VCPU, including
after the VCPU has been run. This will reset the VCPU to its initial
state."

(I notice that api.txt is inconsistent about using "vcpu" or "VCPU"
or "vCPU"... do we have a preference for new text?)

> +
>  Possible features:
>         - KVM_ARM_VCPU_POWER_OFF: Starts the CPU in a power-off state.
>           Depends on KVM_CAP_ARM_PSCI.  If not set, the CPU will be powered on

Do you have to use the same set of feature flags for second and
subsequent VCPU_INIT calls, or can they be different each time?

thanks
-- PMM