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

[Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>]

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;
+
 	return 0;
 }
 
-- 
2.30.2