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Subject: Re: [PATCH v4] virtio-net: enable configurable tx queue size
On Wed, Jun 28, 2017 at 10:37:59AM +0800, 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 crosses a MemoryRegion thereby > generating more than 1024 iovs after translation from guest-physical > address in the backend. > > Signed-off-by: Wei Wang <wei.w.wang@intel.com> I was going to apply this, but run into a host of issues: This segfaults: $ ./x86_64-softmmu/qemu-system-x86_64 -device virtio-net,tx_queue_size=1024 Segmentation fault (core dumped) I tried to tweak this code a bit to avoid the crash, and I run into a further issue: $ ./x86_64-softmmu/qemu-system-x86_64 -device virtio-net,tx_queue_size=1024 Bad ram offset aa49002 Aborted (core dumped) the second issue is especially concerning. > --- > hw/net/virtio-net.c | 32 ++++++++++++++++++++++++++++++-- > include/hw/virtio/virtio-net.h | 1 + > 2 files changed, 31 insertions(+), 2 deletions(-) > > diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c > index 91eddaf..a1fc0db 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 > +#define VIRTIO_NET_TX_QUEUE_DEFAULT_SIZE 256 > + > /* for now, only allow larger queues; with virtio-1, guest can downsize */ > #define VIRTIO_NET_RX_QUEUE_MIN_SIZE VIRTIO_NET_RX_QUEUE_DEFAULT_SIZE > +#define VIRTIO_NET_TX_QUEUE_MIN_SIZE VIRTIO_NET_TX_QUEUE_DEFAULT_SIZE > > /* > * Calculate the number of bytes up to and including the given 'field' of > @@ -1508,15 +1511,18 @@ static void virtio_net_add_queue(VirtIONet *n, int index) > > n->vqs[index].rx_vq = virtio_add_queue(vdev, n->net_conf.rx_queue_size, > virtio_net_handle_rx); > + > if (n->net_conf.tx && !strcmp(n->net_conf.tx, "timer")) { > n->vqs[index].tx_vq = > - virtio_add_queue(vdev, 256, virtio_net_handle_tx_timer); > + virtio_add_queue(vdev, n->net_conf.tx_queue_size, > + virtio_net_handle_tx_timer); > n->vqs[index].tx_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, > virtio_net_tx_timer, > &n->vqs[index]); > } else { > n->vqs[index].tx_vq = > - virtio_add_queue(vdev, 256, virtio_net_handle_tx_bh); > + virtio_add_queue(vdev, n->net_conf.tx_queue_size, > + virtio_net_handle_tx_bh); > n->vqs[index].tx_bh = qemu_bh_new(virtio_net_tx_bh, &n->vqs[index]); > } > > @@ -1927,6 +1933,17 @@ static void virtio_net_device_realize(DeviceState *dev, Error **errp) > return; > } > > + if (n->net_conf.tx_queue_size < VIRTIO_NET_TX_QUEUE_MIN_SIZE || > + n->net_conf.tx_queue_size > VIRTQUEUE_MAX_SIZE || > + !is_power_of_2(n->net_conf.tx_queue_size)) { > + error_setg(errp, "Invalid tx_queue_size (= %" PRIu16 "), " > + "must be a power of 2 between %d and %d", > + n->net_conf.tx_queue_size, VIRTIO_NET_TX_QUEUE_MIN_SIZE, > + VIRTQUEUE_MAX_SIZE); > + virtio_cleanup(vdev); > + return; > + } > + > n->max_queues = MAX(n->nic_conf.peers.queues, 1); > if (n->max_queues * 2 + 1 > VIRTIO_QUEUE_MAX) { > error_setg(errp, "Invalid number of queues (= %" PRIu32 "), " > @@ -1947,6 +1964,15 @@ static void virtio_net_device_realize(DeviceState *dev, Error **errp) > error_report("Defaulting to \"bh\""); > } > > + /* > + * Currently, backends other than vhost-user don't support 1024 queue > + * size. > + */ > + if (n->net_conf.tx_queue_size == VIRTQUEUE_MAX_SIZE && I'd prefer >= here. > + n->nic_conf.peers.ncs[0]->info->type != NET_CLIENT_DRIVER_VHOST_USER) { > + n->net_conf.tx_queue_size = VIRTIO_NET_TX_QUEUE_DEFAULT_SIZE; > + } > + > for (i = 0; i < n->max_queues; i++) { > virtio_net_add_queue(n, i); > } > @@ -2106,6 +2132,8 @@ static Property virtio_net_properties[] = { > DEFINE_PROP_STRING("tx", VirtIONet, net_conf.tx), > DEFINE_PROP_UINT16("rx_queue_size", VirtIONet, net_conf.rx_queue_size, > VIRTIO_NET_RX_QUEUE_DEFAULT_SIZE), > + DEFINE_PROP_UINT16("tx_queue_size", VirtIONet, net_conf.tx_queue_size, > + VIRTIO_NET_TX_QUEUE_DEFAULT_SIZE), > DEFINE_PROP_UINT16("host_mtu", VirtIONet, net_conf.mtu, 0), > DEFINE_PROP_BOOL("x-mtu-bypass-backend", VirtIONet, mtu_bypass_backend, > true), > diff --git a/include/hw/virtio/virtio-net.h b/include/hw/virtio/virtio-net.h > index 602b486..b81b6a4 100644 > --- a/include/hw/virtio/virtio-net.h > +++ b/include/hw/virtio/virtio-net.h > @@ -36,6 +36,7 @@ typedef struct virtio_net_conf > int32_t txburst; > char *tx; > uint16_t rx_queue_size; > + uint16_t tx_queue_size; > uint16_t mtu; > } virtio_net_conf; > > -- > 2.7.4
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