Re: [dpdk-dev] [RFC 1/2] vhost: add packed ring support to vring base requests

[Maxime Coquelin <maxime.coquelin@redhat.com>]

Hi Jens,

On 08/10/2018 09:09 AM, Jens Freimann wrote:
> On Wed, Aug 08, 2018 at 05:23:22PM +0200, Maxime Coquelin wrote:
>> For consistency with Vhost kernel backend, save the wrap
>> counter value into bit 31 of num's vring state field.
>>
>> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
>> ---
>> lib/librte_vhost/vhost_user.c | 16 ++++++++++++----
>> 1 file changed, 12 insertions(+), 4 deletions(-)
>>
>> diff --git a/lib/librte_vhost/vhost_user.c 
>> b/lib/librte_vhost/vhost_user.c
>> index a2d4c9ffc..31cfdf163 100644
>> --- a/lib/librte_vhost/vhost_user.c
>> +++ b/lib/librte_vhost/vhost_user.c
>> @@ -648,10 +648,15 @@ static int
>> vhost_user_set_vring_base(struct virtio_net *dev,
>>               VhostUserMsg *msg)
>> {
>> -    dev->virtqueue[msg->payload.state.index]->last_used_idx  =
>> -            msg->payload.state.num;
>> -    dev->virtqueue[msg->payload.state.index]->last_avail_idx =
>> -            msg->payload.state.num;
>> +    struct vhost_virtqueue *vq = 
>> dev->virtqueue[msg->payload.state.index];
>> +    if (dev->features & (1ULL << VIRTIO_F_RING_PACKED)) {
>> +        vq->avail_wrap_counter = msg->payload.state.num >> 31;
>> +        vq->used_wrap_counter = vq->avail_wrap_counter;
> 
> Maybe I don't understand when this is called, but the wrap counters
> could have different values, no?

No, because we set the used index to the saved avail index value, so
wrap counters must be the same.

> Apart from that:
> 
> Reviewed-by: Jens Freimann <jfreimann@redhat.com>
> regards,
> Jens