Re: [dpdk-dev] [PATCH 4/8] net/virtio: allocate queue at init stage

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

On 11/03/2016 05:09 PM, Yuanhan Liu wrote:
> Queue allocation should be done once, since the queue related info (such
> as vring addreess) will only be informed to the vhost-user backend once
> without virtio device reset.
>
> That means, if you allocate queues again after the vhost-user negotiation,
> the vhost-user backend will not be informed any more. Leading to a state
> that the vring info mismatches between virtio PMD driver and vhost-backend:
> the driver switches to the new address has just been allocated, while the
> vhost-backend still sticks to the old address has been assigned in the init
> stage.
>
> Unfortunately, that is exactly how the virtio driver is coded so far: queue
> allocation is done at queue_setup stage (when rte_eth_tx/rx_queue_setup is
> invoked). This is wrong, because queue_setup can be invoked several times.
> For example,
>
>     $ start_testpmd.sh ... --txq=1 --rxq=1 ...
>     > port stop 0
>     > port config all txq 1 # just trigger the queue_setup callback again
>     > port config all rxq 1
>     > port start 0
>
> The right way to do is allocate the queues in the init stage, so that the
> vring info could be persistent with the vhost-user backend.
>
> Besides that, we should allocate max_queue pairs the device supports, but
> not nr queue pairs firstly configured, to make following case work.
>
>     $ start_testpmd.sh ... --txq=1 --rxq=1 ...
>     > port stop 0
>     > port config all txq 2
>     > port config all rxq 2
>     > port start 0
>
> Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
> ---
>  drivers/net/virtio/virtio_ethdev.c | 105 +++++++++++++++++++++++--------------
>  drivers/net/virtio/virtio_ethdev.h |   8 ---
>  drivers/net/virtio/virtio_pci.h    |   2 +
>  drivers/net/virtio/virtio_rxtx.c   |  38 +++++++-------
>  4 files changed, 85 insertions(+), 68 deletions(-)
>

Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>

Thanks,
Maxime