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

[Peter Maydell]

On 2 December 2014 at 14:47, Christoffer Dall
<christoffer.dall at linaro.org> wrote:
> On Thu, Nov 27, 2014 at 10:53:50PM +0000, Peter Maydell wrote:
>> On 27 November 2014 at 18:40, Christoffer Dall
>> <christoffer.dall at linaro.org> wrote:
>> >  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?
>>
> That's a good question.  Do you have any opinion on the matter?

QEMU always will, so I'd be happy if we said it has to be the same
set of flags each time. I guess I'd go for "say they have to match";
we can always relax later if we need to.

> It seems weird to change the target of a Vcpu from some core to another
> core, but there is not reason why you shouldn't be able to set a vCpU to
> be powered off when run, just because it wasn't earlier on, is
> there?

We need an API for get/set of PSCI power state for migration
anyhow, so it's not inherently required to be able to flip
this bit on reset.

-- PMM