Re: [PATCH 1/2] xen/arm: remove workaround to inject evtchn_irq on irq enable

[Julien Grall <julien.grall@linaro.org>]

On 07/02/2014 04:38 PM, Ian Campbell wrote:
> On Wed, 2014-06-25 at 16:03 +0100, Julien Grall wrote:
>> Hi Stefano,
>>
>> On 06/24/2014 07:11 PM, Stefano Stabellini wrote:
>>> evtchn_upcall_pending is already set by common code at vcpu creation,
>>> therefore on ARM we also need to call vgic_vcpu_inject_irq for it.
>>> Currently we do that from vgic_enable_irqs as a workaround.
>>>
>>> Do this properly by calling vgic_vcpu_inject_irq in the appropriate
>>> places at vcpu creation time, making sure to call it after the vcpu is
>>> up (_VPF_down has been cleared).
>>
>> While it's works perfectly on common case, as the toolstack is always
>> setting VGCF_online.
>>
>> It would be possible to call the hypercall DOMCTL_vcpusetcontext without
>> this flags enable. If so, the new VCPU will never receive event channel
>> interrupt.
> 
> I think the only other way to clear _VPF_down is the psci code, so I
> suppose it needs a kick too.

The function PSCI on will call arch_set_info_guest directly with
VGCF_online.

> The other option is VCPUOP_up whch we do not support (or wire up) on
> ARM.

Hmmm... right I was looking directly to do_vcpu_op, but we have an extra
layer on ARM (do_arm_vcpu_op).

In this case, I would return an error if VGCF_online is not set. I will
allow us to catch easily an error later if we decide to implement VCPUOP_up.

Regards,

-- 
Julien Grall