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Subject: Re: [Qemu-devel] [PATCH v3 1/2] virtio-net: enable configurable tx queue size
On 06/26/2017 11:18 AM, Jason Wang wrote:
On 2017年06月23日 10:32, Wei Wang wrote:This patch enables the virtio-net tx queue size to be configurable between 256 (the default queue size) and 1024 by the user when the vhost-user backend is used. Currently, the maximum tx queue size for other backends is 512 due to the following limitations: - QEMU backend: the QEMU backend implementation in some cases may send 1024+1 iovs to writev. - Vhost_net backend: there are possibilities that the guest sends a vring_desc of memory which corsses a MemoryRegion thereby generating more than 1024 iovs after translattion from guest-physical address in the backend. Signed-off-by: Wei Wang <wei.w.wang@intel.com> ---hw/net/virtio-net.c | 45 +++++++++++++++++++++++++++++++++---------include/hw/virtio/virtio-net.h | 1 + 2 files changed, 37 insertions(+), 9 deletions(-) diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c index 91eddaf..d13ca60 100644 --- a/hw/net/virtio-net.c +++ b/hw/net/virtio-net.c @@ -34,8 +34,11 @@ /* previously fixed value */ #define VIRTIO_NET_RX_QUEUE_DEFAULT_SIZE 256 + + /*+ * Currently, backends other than vhost-user don't support 1024 queue+ * size. + */ + if (n->net_conf.tx_queue_size == VIRTQUEUE_MAX_SIZE && + nc->peer->info->type != NET_CLIENT_DRIVER_VHOST_USER) { + n->net_conf.tx_queue_size = VIRTIO_NET_TX_QUEUE_DEFAULT_SIZE;Do we really want assume all vhost-user backend support 1024 queue size?
Do you know any vhost-user backend implementation that doesn't support 1024 tx queue size?
+ } + + for (i = 0; i < n->max_queues; i++) { + virtio_net_add_queue(n, i); + }Any reason to move virtio_net_add_queue() here?
Please check the whole init steps. It was moved here (after qemu_new_nic()) to make sure nc->peer is not NULL. Best, Wei
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