[dpdk-dev] [PATCH 2/4] vhost: introduce vhost_log_write

[Yuanhan Liu]

On Wed, Dec 09, 2015 at 05:44:11AM +0000, Xie, Huawei wrote:
> On 12/9/2015 11:41 AM, Yuanhan Liu wrote:
> > On Wed, Dec 09, 2015 at 03:33:16AM +0000, Xie, Huawei wrote:
> > ...
> >>>> +static inline void __attribute__((always_inline))
> >>>> +vhost_log_write(struct virtio_net *dev, struct vhost_virtqueue *vq,
> >>>> +		uint64_t offset, uint64_t len)
> >>>> +{
> >>>> +	uint64_t addr = vq->log_guest_addr;
> >>>> +	uint64_t page;
> >>>> +
> >>>> +	if (unlikely(((dev->features & (1ULL << VHOST_F_LOG_ALL)) == 0) ||
> >>>> +		     !dev->log_base || !len))
> >>>> +		return;
> >>> Isn't "likely" more appropriate in above, since the whole
> >>> expression is expected to be true most of the time?
> >> Victor:
> >> So we are not always logging, what is the message that tells the backend
> >> the migration is started?
> > When log starts, VHOST_USER_SET_FEATURES request will be sent again,
> > with VHOST_F_LOG_ALL feature bit set.
> As the VHOST_USER_SET_FEATURES handling and rx/tx runs asynchronously,
> we have to make sure we don't miss logging anything when this feature is
> set.

That's a good remind. Thanks.

> For example, I doubt like in virtio_dev_rx, is the dev->features
> volatile?

No, it is not volatile.

	--yliu