<div dir="auto">Don't use int as a boolean. Use bool. Ideally find unused pad hole for it</div> <div class="gmail_quote gmail_quote_container"><div dir="ltr" class="gmail_attr">On Fri, Jul 17, 2026, 11:59 AM Maxime Leroy <<a href="mailto:maxime@leroys.fr">maxime@leroys.fr</a>> wrote: </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">The tap Rx path is driven by a SIGIO trigger: pmd_rx_burst() returns without reading the queue fd unless tap_trigger, bumped by the O_ASYNC signal handler, has advanced. That avoids a readv() on every empty poll. In Rx interrupt mode the application blocks on the queue fd through epoll and polls only after a wakeup. The epoll wakeup and the trigger are distinct signals, so the burst can return 0 right after a wakeup because the trigger has not advanced, leaving the fd readable with no further edge: traffic stalls. When the port is configured for Rx interrupts, drain the fd unconditionally in the burst and do not arm the SIGIO trigger on the data queue fd. A data queue fd can be closed and recreated on a later setup, so the mode must stay constant to keep every fd on the same SIGIO policy: it is fixed at configure time and a later change is rejected. Close and reopen the port to switch modes. Fixes: 4870a8cdd968 ("net/tap: support Rx interrupt") Cc: <a href="mailto:stable@dpdk.org" target="_blank" rel="noreferrer">stable@dpdk.org</a> Signed-off-by: Maxime Leroy <<a href="mailto:maxime@leroys.fr" target="_blank" rel="noreferrer">maxime@leroys.fr</a>> --- drivers/net/tap/rte_eth_tap.c | 18 +++++++++++++++++- drivers/net/tap/rte_eth_tap.h | 2 ++ 2 files changed, 19 insertions(+), 1 deletion(-) diff --git a/drivers/net/tap/rte_eth_tap.c b/drivers/net/tap/rte_eth_tap.c index 99ede19e49..ea9ef76335 100644 --- a/drivers/net/tap/rte_eth_tap.c +++ b/drivers/net/tap/rte_eth_tap.c @@ -254,6 +254,10 @@ tun_alloc(struct pmd_internals *pmd, int is_keepalive, int persistent) goto error; } + /* interrupt mode wakes through epoll on the data queue fd, not the SIGIO trigger */ + if (pmd->intr_mode) + return fd; + /* Find a free realtime signal */ for (signo = SIGRTMIN + 1; signo < SIGRTMAX; signo++) { struct sigaction sa; @@ -477,7 +481,7 @@ pmd_rx_burst(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts) unsigned long num_rx_bytes = 0; uint32_t trigger = tap_trigger; - if (trigger == rxq->trigger_seen) + if (!rxq->intr_mode && trigger == rxq->trigger_seen) return 0; process_private = rte_eth_devices[rxq->in_port].process_private; @@ -937,6 +941,16 @@ tap_dev_configure(struct rte_eth_dev *dev) struct pmd_internals *pmd = dev->data->dev_private; int intr_mode = !!dev->data->dev_conf.intr_conf.rxq; + /* The queue fd is created once and its SIGIO trigger is armed for poll + * mode only; the interrupt mode cannot be toggled on an existing port. + */ + if (pmd->intr_mode_set && pmd->intr_mode != intr_mode) { + TAP_LOG(ERR, + "%s: Rx interrupt mode is fixed after configure, close and reopen the port to change it", + dev->device->name); + return -ENOTSUP; + } + if (dev->data->nb_rx_queues != dev->data->nb_tx_queues) { TAP_LOG(ERR, "%s: number of rx queues %d must be equal to number of tx queues %d", @@ -947,6 +961,7 @@ tap_dev_configure(struct rte_eth_dev *dev) } pmd->intr_mode = intr_mode; + pmd->intr_mode_set = 1; TAP_LOG(INFO, "%s: %s: TX configured queues number: %u", dev->device->name, pmd->name, dev->data->nb_tx_queues); @@ -1620,6 +1635,7 @@ tap_rx_queue_setup(struct rte_eth_dev *dev, rxq->queue_id = rx_queue_id; rxq->max_rx_segs = max_rx_segs; rxq->rxmode = &dev->data->dev_conf.rxmode; + rxq->intr_mode = internals->intr_mode; dev->data->rx_queues[rx_queue_id] = rxq; int fd = tap_setup_queue(dev, rx_queue_id, 1); diff --git a/drivers/net/tap/rte_eth_tap.h b/drivers/net/tap/rte_eth_tap.h index 3180719c34..abe22aac9f 100644 --- a/drivers/net/tap/rte_eth_tap.h +++ b/drivers/net/tap/rte_eth_tap.h @@ -50,6 +50,7 @@ struct rx_queue { uint16_t queue_id; /* queue ID*/ struct queue_stats stats; /* Stats for this RX queue */ uint16_t max_rx_segs; /* max scatter segments per packet */ + uint16_t intr_mode; /* 1 when Rx queue interrupts are used */ struct rte_eth_rxmode *rxmode; /* RX features */ struct rte_mbuf *pool; /* mbufs pool for this queue */ struct tun_pi pi; /* packet info for iovecs */ @@ -94,6 +95,7 @@ struct pmd_internals { struct rte_intr_handle *intr_handle; /* LSC interrupt handle. */ int intr_mode; /* Rx queue interrupt mode */ + int intr_mode_set; /* intr_mode locked after configure */ int ka_fd; /* keep-alive file descriptor */ struct rte_mempool *gso_ctx_mp; /* Mempool for GSO packets */ }; -- 2.43.0 </blockquote></div>