Re: In l4vcpu_irq_restore function don't use l4vcpu_irq_disable(vcpu)

On 10/16/2012 02:04 PM, Ildar Ismagilov wrote:
> In function l4vcpu_irq_restore on l4/pkg/libvcpu/include/vcpu.h file:
>
> L4_CV L4_INLINE
> void
> l4vcpu_irq_restore(l4_vcpu_state_t *vcpu, l4vcpu_irq_state_t s,
>                     l4_utcb_t *utcb,
>                     l4vcpu_event_hndl_t do_event_work_cb,
>                     l4vcpu_setup_ipc_t setup_ipc) L4_NOTHROW
> {
>    if (s & L4_VCPU_F_IRQ)
>      l4vcpu_irq_enable(vcpu, utcb, do_event_work_cb, setup_ipc);
> }
>
> why don't call  l4vcpu_irq_disable(vcpu) if "s" variable don't include
> L4_VCPU_F_IRQ flag?
>
> possible should be so:
>
> L4_CV L4_INLINE
> void
> l4vcpu_irq_restore(l4_vcpu_state_t *vcpu, l4vcpu_irq_state_t s,
>                     l4_utcb_t *utcb,
>                     l4vcpu_event_hndl_t do_event_work_cb,
>                     l4vcpu_setup_ipc_t setup_ipc) L4_NOTHROW
> {
>    if (s & L4_VCPU_F_IRQ)
>      l4vcpu_irq_enable(vcpu, utcb, do_event_work_cb, setup_ipc);
>    else
>      l4vcpu_irq_disable(vcpu);
> }
>

Hi Ildar,

your way of writing it is also valid, but that would be an unnecesseary 
call. Here is why:
You can only get a (valid) state to restore by a call to 
l4vcpu_irq_disable_save, so IRQs in your vcpu are disabled.

When you now call l4vcpu_irq_restore and you want to restore a state 
with disabled IRQs, you don't need to change anything. If you want to 
restore a state with enabled IRQs, then IRQs get enabled.


Regards,
Philipp