From 945884f14b2ae692754f92e46b190be3a8f6cdc5 Mon Sep 17 00:00:00 2001 From: Stephen Hemminger Date: Mon, 20 Jul 2015 11:40:45 -0700 Subject: [PATCH] virtio: fix queue size and number of descriptors The virtual queue ring size and the number of slots actually usable are separate parameters. In the most common environment (QEMU) the virtual queue ring size is 256, but some environments the ring maybe much larger. The ring size comes from the host and the driver must use the actual size passed. The number of descriptors can be either zero to use the whole available ring, or some value smaller. This is used to limit the number of mbufs allocated for the receive ring. If more descriptors are requested than available the size is silently truncated. Note: the ring size (from host) must be a power of two, but the number of descriptors used can be any size from 1 to the size of the virtual ring. Fixes: d78deadae4dc ("virtio: fix ring size negotiation") Reported-by: Changchun Ouyang Signed-off-by: Stephen Hemminger Acked-by: Changchun Ouyang --- drivers/net/virtio/virtio_ethdev.c | 17 ++++------------- 1 file changed, 4 insertions(+), 13 deletions(-) diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c index 9ca9bb265b..d460d894a7 100644 --- a/drivers/net/virtio/virtio_ethdev.c +++ b/drivers/net/virtio/virtio_ethdev.c @@ -276,8 +276,6 @@ int virtio_dev_queue_setup(struct rte_eth_dev *dev, */ vq_size = VIRTIO_READ_REG_2(hw, VIRTIO_PCI_QUEUE_NUM); PMD_INIT_LOG(DEBUG, "vq_size: %d nb_desc:%d", vq_size, nb_desc); - if (nb_desc == 0) - nb_desc = vq_size; if (vq_size == 0) { PMD_INIT_LOG(ERR, "%s: virtqueue does not exist", __func__); return -EINVAL; @@ -288,16 +286,6 @@ int virtio_dev_queue_setup(struct rte_eth_dev *dev, return -EINVAL; } - if (nb_desc < vq_size) { - if (!rte_is_power_of_2(nb_desc)) { - PMD_INIT_LOG(ERR, - "nb_desc(%u) size is not powerof 2", - nb_desc); - return -EINVAL; - } - vq_size = nb_desc; - } - if (queue_type == VTNET_RQ) { snprintf(vq_name, sizeof(vq_name), "port%d_rvq%d", dev->data->port_id, queue_idx); @@ -325,7 +313,10 @@ int virtio_dev_queue_setup(struct rte_eth_dev *dev, vq->queue_id = queue_idx; vq->vq_queue_index = vtpci_queue_idx; vq->vq_nentries = vq_size; - vq->vq_free_cnt = vq_size; + + if (nb_desc == 0 || nb_desc > vq_size) + nb_desc = vq_size; + vq->vq_free_cnt = nb_desc; /* * Reserve a memzone for vring elements -- 2.20.1