Linux Virtualization - Jun 2015 - virtio-net: why not always to set avail->flags to VRING_AVAIL_F_NO_INTERRUPT

Hi,

I'm a newbie and have a question about vring_new_virtqueue function.

Why we set avail->flags to VRING_AVAIL_F_NO_INTERRUPT when no callbacks?
I think we should set avail->flags to VRING_AVAIL_F_NO_INTERRUPT even if no
callbacks.

Linhaifeng <haifeng.lin at huawei.com> writes:
> Hi,
>
> I'm a newbie and have a question about vring_new_virtqueue function.
>
> Why we set avail->flags to VRING_AVAIL_F_NO_INTERRUPT when no callbacks?
> I think we should set avail->flags to VRING_AVAIL_F_NO_INTERRUPT even if
no callbacks.
Hi Linhaifeng,

        Not sure I understand your question, but I'll try to answer.

We don't set VRING_AVAIL_F_NO_INTERRUPT if there's a callback because we
want that callback called.  Otherwise callback will never be used.

Cheers,
Rusty.

On 2015/6/4 9:13, Rusty Russell wrote:
> Linhaifeng <haifeng.lin at huawei.com> writes:
>> Hi,
>>
>> I'm a newbie and have a question about vring_new_virtqueue
function.
>>
>> Why we set avail->flags to VRING_AVAIL_F_NO_INTERRUPT when no
callbacks?
>> I think we should set avail->flags to VRING_AVAIL_F_NO_INTERRUPT
even if no callbacks.
> 
> Hi Linhaifeng,
> 
>         Not sure I understand your question, but I'll try to answer.
> 
> We don't set VRING_AVAIL_F_NO_INTERRUPT if there's a callback
because we
> want that callback called.  Otherwise callback will never be used.
> 
> Cheers,
> Rusty.
> 
> 
Hi Rusty,

Thank you for your response.

I mean should we set VRING_AVAIL_F_NO_INTERRUPT when virtqueue is initialized
whether there is callback or not?
As it would be set in function virtqueue_disable_cb and
virtqueue_enable_cb_prepare later.

Regards,
Haifeng