Re: [dpdk-dev] [PATCH] net/virtio: report max/min/align desc limits in dev info get

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

On 9/14/21 8:43 AM, Andrew Rybchenko wrote:
> On 9/13/21 10:52 PM, Maxime Coquelin wrote:
>>
>>
>> On 8/20/21 2:48 PM, Andrew Rybchenko wrote:
>>> From: Ivan Ilchenko <ivan.ilchenko@oktetlabs.ru>
>>>
>>> Report max/min/align descriptors limits in device info get callback.
>>> Before calling the callback, rte_eth_dev_info_get() provides
>>> default values of nb_min as zero and nb_max as UINT16_MAX that are
>>> not correct for the driver, so one can't rely on them.
>>>
>>> Signed-off-by: Ivan Ilchenko <ivan.ilchenko@oktetlabs.ru>
>>> Signed-off-by: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
>>> ---
>>>  drivers/net/virtio/virtio_ethdev.c | 25 +++++++++++++++++++++++++
>>>  1 file changed, 25 insertions(+)
>>>
>>> diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c
>>> index e58085a2c9..601c03e079 100644
>>> --- a/drivers/net/virtio/virtio_ethdev.c
>>> +++ b/drivers/net/virtio/virtio_ethdev.c
>>> @@ -33,6 +33,7 @@
>>>  #include "virtio_logs.h"
>>>  #include "virtqueue.h"
>>>  #include "virtio_rxtx.h"
>>> +#include "virtio_rxtx_simple.h"
>>>  #include "virtio_user/virtio_user_dev.h"
>>>  
>>>  static int  virtio_dev_configure(struct rte_eth_dev *dev);
>>> @@ -2536,6 +2537,30 @@ virtio_dev_info_get(struct rte_eth_dev *dev, struct rte_eth_dev_info *dev_info)
>>>  	if ((host_features & tso_mask) == tso_mask)
>>>  		dev_info->tx_offload_capa |= DEV_TX_OFFLOAD_TCP_TSO;
>>>  
>>> +	if (host_features & (1ULL << VIRTIO_F_RING_PACKED)) {
>>> +		/*
>>> +		 * According to 2.7 Packed Virtqueues,
>>> +		 * 2.7.10.1 Structure Size and Alignment:
>>> +		 * The Queue Size value does not have to be a power of 2.
>>> +		 */
>>> +		dev_info->rx_desc_lim.nb_max = UINT16_MAX;
>>> +	} else {
>>> +		/*
>>> +		 * According to 2.6 Split Virtqueues:
>>> +		 * Queue Size value is always a power of 2. The maximum Queue
>>> +		 * Size value is 32768.
>>> +		 */
>>> +		dev_info->rx_desc_lim.nb_max = 32768;
>>> +	}
>>> +	/*
>>> +	 * Actual minimum is not the same for virtqueues of different kinds,
>>> +	 * but to avoid tangling the code with separate branches, rely on
>>> +	 * default thresholds since desc number must be at least of their size.
>>> +	 */
>>> +	dev_info->rx_desc_lim.nb_min = RTE_MAX(DEFAULT_RX_FREE_THRESH,
>>> +					       RTE_VIRTIO_VPMD_RX_REARM_THRESH);
>>> +	dev_info->rx_desc_lim.nb_align = 1;
>>> +
>>
>> It makes sense, but shouldn't we do the same for dev_info->tx_desc_lim?
> 
> Yes, you're right. We'll care about it.
> 
> I suggest to add "Rx" in the summary and care about Tx in a
> subsequent patch.
> 
> net/virtio: report max/min/align Rx desc limits in dev info
> 
> OK?
> 

Works for me! I will fix the title while applying.

Thanks,
Maxime