On Tue, Jun 16, 2026 at 02:51:20PM +0200, Laurent Vivier wrote:
Allow the guest to negotiate multiple virtqueue pairs by advertising VIRTIO_NET_F_MQ and VHOST_USER_PROTOCOL_F_MQ feature flags, and increase VHOST_USER_MAX_VQS from 2 to 32, supporting up to 16 queue pairs.
Replace the VHOST_USER_RX_QUEUE, VHOST_USER_TX_QUEUE, VHOST_USER_IS_QUEUE_TX(), and VHOST_USER_IS_QUEUE_RX() macros with a general set of QPAIR_* macros in passt.h that translate between queue pair numbers and virtqueue indices. These are needed now that queue indices are no longer limited to 0 and 1.
Add a queue pair parameter to vu_send_single(), propagating it to the virtqueue selection. All callers currently pass QPAIR_DEFAULT (0): only the first RX queue is used for receiving. The guest kernel selects which TX queue to use for transmission. Full multi-RX-queue load balancing will be implemented separately.
Signed-off-by: Laurent Vivier
A handful of comments, but they're all more or less cosmetic.
--- passt.h | 8 ++++++++ tap.c | 9 ++++++--- tcp_vu.c | 7 +++++-- udp_vu.c | 3 ++- vhost_user.c | 14 +++++++++----- vhost_user.h | 9 --------- virtio.h | 2 +- vu_common.c | 17 +++++++++++------ vu_common.h | 3 ++- 9 files changed, 44 insertions(+), 28 deletions(-)
diff --git a/passt.h b/passt.h index 07126a969551..bf8a1e037317 100644 --- a/passt.h +++ b/passt.h @@ -28,6 +28,14 @@ union epoll_ref; #include "udp.h" #include "vhost_user.h"
+/* Queue pairs consist of one RX queue (even index) and one TX queue (odd index). + * Example: pair 0 has RX queue 0 and TX queue 1; pair 1 has RX queue 2 and TX queue 3. + */ +#define QPAIR_DEFAULT 0 /* Default queue pair */ +#define QPAIR_FROMGUEST_QUEUE(qpair) ((size_t)(qpair) * 2 + 1) /* TX queue index from pair */ +#define QPAIR_TOGUEST_QUEUE(qpair) ((size_t)(qpair) * 2) /* RX queue index from pair */ +#define QPAIR_FROM_QUEUE(queue) ((queue) / 2) /* Extract pair from queue */ + /* Default address for our end on the tap interface. Bit 0 of byte 0 must be 0 * (unicast) and bit 1 of byte 1 must be 1 (locally administered). Otherwise * it's arbitrary. diff --git a/tap.c b/tap.c index 4699c5ef9177..a5d22088424f 100644 --- a/tap.c +++ b/tap.c @@ -155,7 +155,7 @@ void tap_send_single(const struct ctx *c, const void *data, size_t l2len) tap_send_frames(c, iov, iovcnt, 1); break; case MODE_VU: - vu_send_single(c, data, l2len); + vu_send_single(c, QPAIR_DEFAULT, data, l2len); break; } } @@ -1379,8 +1379,11 @@ static void tap_backend_show_hints(const struct ctx *c) break; case MODE_VU: info("You can start qemu with:"); - info(" kvm ... -chardev socket,id=chr0,path=%s -netdev vhost-user,id=netdev0,chardev=chr0 -device virtio-net,netdev=netdev0 -object memory-backend-memfd,id=memfd0,share=on,size=$RAMSIZE -numa node,memdev=memfd0\n", - c->sock_path); + info(" kvm ... -chardev socket,id=chr0,path=%s " + "-netdev vhost-user,id=netdev0,chardev=chr0,queues=$QUEUES " + "-device virtio-net,netdev=netdev0,mq=true " + "-object memory-backend-memfd,id=memfd0,share=on,size=$RAMSIZE " + "-numa node,memdev=memfd0\n", c->sock_path); break; } } diff --git a/tcp_vu.c b/tcp_vu.c index 7e2a7dbc81e1..9ef6b5242c9c 100644 --- a/tcp_vu.c +++ b/tcp_vu.c @@ -124,7 +124,8 @@ static int tcp_vu_send_dup(const struct ctx *c, struct vu_virtq *vq, int tcp_vu_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags) { struct vu_dev *vdev = c->vdev; - struct vu_virtq *vq = &vdev->vq[VHOST_USER_RX_QUEUE]; + int rx_queue = QPAIR_TOGUEST_QUEUE(QPAIR_DEFAULT);
Nit: I like the "toguest" terminology in the macro, but the variable name still uses the somewhat confusing "rx" term. Since this is a strictly to-guest function, would just "queue" or "qindex" do?
+ struct vu_virtq *vq = &vdev->vq[rx_queue]; size_t optlen, hdrlen, iov_cnt, iov_used; struct vu_virtq_element flags_elem[2]; struct iov_tail payload, l2frame; @@ -429,8 +430,10 @@ static void tcp_vu_prepare(const struct ctx *c, struct tcp_tap_conn *conn, int tcp_vu_data_from_sock(const struct ctx *c, struct tcp_tap_conn *conn) { uint32_t wnd_scaled = conn->wnd_from_tap << conn->ws_from_tap; + unsigned int qpair = QPAIR_DEFAULT; + int rx_queue = QPAIR_TOGUEST_QUEUE(qpair);
Ditto.
struct vu_dev *vdev = c->vdev; - struct vu_virtq *vq = &vdev->vq[VHOST_USER_RX_QUEUE]; + struct vu_virtq *vq = &vdev->vq[rx_queue]; uint32_t already_sent, check; ssize_t len, previous_dlen; int i, elem_cnt, frame_cnt; diff --git a/udp_vu.c b/udp_vu.c index e4fb105730bf..b1a8ad76a691 100644 --- a/udp_vu.c +++ b/udp_vu.c @@ -147,8 +147,9 @@ void udp_vu_sock_to_tap(const struct ctx *c, int s, int n, flow_sidx_t tosidx) bool v6 = !(inany_v4(&toside->eaddr) && inany_v4(&toside->oaddr)); static struct vu_virtq_element elem[VIRTQUEUE_MAX_SIZE]; static struct iovec iov_vu[VIRTQUEUE_MAX_SIZE]; + int rx_queue = QPAIR_TOGUEST_QUEUE(QPAIR_DEFAULT);
Ditto.
struct vu_dev *vdev = c->vdev; - struct vu_virtq *vq = &vdev->vq[VHOST_USER_RX_QUEUE]; + struct vu_virtq *vq = &vdev->vq[rx_queue]; size_t hdrlen = udp_vu_hdrlen(v6); int i;
diff --git a/vhost_user.c b/vhost_user.c index a1259c2624c0..fa13c66d5f0d 100644 --- a/vhost_user.c +++ b/vhost_user.c @@ -324,6 +324,7 @@ static bool vu_get_features_exec(struct vu_dev *vdev, 1ULL << VIRTIO_F_VERSION_1 | 1ULL << VIRTIO_NET_F_GUEST_CSUM | 1ULL << VIRTIO_NET_F_MRG_RXBUF | + 1ULL << VIRTIO_NET_F_MQ | 1ULL << VHOST_F_LOG_ALL | 1ULL << VHOST_USER_F_PROTOCOL_FEATURES;
@@ -770,7 +771,8 @@ static void vu_check_queue_msg_file(struct vhost_user_msg *vmsg) bool nofd = vmsg->payload.u64 & VHOST_USER_VRING_NOFD_MASK;
if (idx >= VHOST_USER_MAX_VQS) - die("Invalid vhost-user queue index: %u", idx); + die("Invalid vhost-user queue index: %u (maximum %u)", idx, + VHOST_USER_MAX_VQS);
Nit: the maximum index should be (VHOST_USER_MAX_VQS - 1), no?
if (nofd) { vmsg_close_fds(vmsg); @@ -812,7 +814,9 @@ static bool vu_set_vring_kick_exec(struct vu_dev *vdev,
vdev->vq[idx].started = true;
- if (vdev->vq[idx].kick_fd != -1 && VHOST_USER_IS_QUEUE_TX(idx)) { + if (vdev->vq[idx].kick_fd != -1 && + QPAIR_FROMGUEST_QUEUE(QPAIR_FROM_QUEUE(idx)) == + (unsigned int)idx) {
This seems a very awkward way of testing if idx is even. AFAICT VHOST_USER_IS_QUEUE_TX() was already correct for multiple qpairs, why remove it? (That said renaming it to QUEUE_IS_FROMGUEST or something would be nice).
vu_set_watch(vdev, idx); debug("Waiting for kicks on fd: %d for vq: %d", vdev->vq[idx].kick_fd, idx); @@ -899,7 +903,8 @@ static bool vu_get_protocol_features_exec(struct vu_dev *vdev, uint64_t features = 1ULL << VHOST_USER_PROTOCOL_F_REPLY_ACK | 1ULL << VHOST_USER_PROTOCOL_F_LOG_SHMFD | 1ULL << VHOST_USER_PROTOCOL_F_DEVICE_STATE | - 1ULL << VHOST_USER_PROTOCOL_F_RARP; + 1ULL << VHOST_USER_PROTOCOL_F_RARP | + 1ULL << VHOST_USER_PROTOCOL_F_MQ;
(void)vdev; vmsg_set_reply_u64(vmsg, features); @@ -938,10 +943,9 @@ static bool vu_get_queue_num_exec(struct vu_dev *vdev, { (void)vdev;
- /* NOLINTNEXTLINE(misc-redundant-expression) */ vmsg_set_reply_u64(vmsg, VHOST_USER_MAX_VQS / 2);
- debug("VHOST_USER_MAX_VQS %u", VHOST_USER_MAX_VQS / 2); + debug("Using up to %u vhost-user queue pairs", VHOST_USER_MAX_VQS / 2);
return true; } diff --git a/vhost_user.h b/vhost_user.h index e806a9e54e00..d2e51d3e86c3 100644 --- a/vhost_user.h +++ b/vhost_user.h @@ -201,15 +201,6 @@ struct vhost_user_msg { } __attribute__ ((__packed__)); #define VHOST_USER_HDR_SIZE sizeof(struct vhost_user_header)
-/* index of the RX virtqueue */ -#define VHOST_USER_RX_QUEUE 0 -/* index of the TX virtqueue */ -#define VHOST_USER_TX_QUEUE 1 - -/* in case of multiqueue, the RX and TX queues are interleaved */ -#define VHOST_USER_IS_QUEUE_TX(n) (n % 2) -#define VHOST_USER_IS_QUEUE_RX(n) (!(n % 2)) - /* Default virtio-net header for passt */ #define VU_HEADER ((struct virtio_net_hdr){ \ .flags = VIRTIO_NET_HDR_F_DATA_VALID, \ diff --git a/virtio.h b/virtio.h index 8f2ae068d5ba..eb7570e63cd7 100644 --- a/virtio.h +++ b/virtio.h @@ -90,7 +90,7 @@ struct vu_dev_region { uint64_t mmap_addr; };
-#define VHOST_USER_MAX_VQS 2U +#define VHOST_USER_MAX_VQS 32U
/* * Set a reasonable maximum number of ram slots, which will be supported by diff --git a/vu_common.c b/vu_common.c index d07f584f228a..8b555ea9a8b1 100644 --- a/vu_common.c +++ b/vu_common.c @@ -175,7 +175,8 @@ static void vu_handle_tx(struct vu_dev *vdev, int index, int out_sg_count; int count;
- assert(VHOST_USER_IS_QUEUE_TX(index)); + assert(QPAIR_FROMGUEST_QUEUE(QPAIR_FROM_QUEUE(index)) == + (unsigned int)index);
Similar comment here.
tap_flush_pools();
@@ -233,28 +234,32 @@ void vu_kick_cb(struct vu_dev *vdev, union epoll_ref ref,
trace("vhost-user: got kick_data: %016"PRIx64" idx: %d", kick_data, ref.queue); - if (VHOST_USER_IS_QUEUE_TX(ref.queue)) + if (QPAIR_FROMGUEST_QUEUE(QPAIR_FROM_QUEUE(ref.queue)) == + (unsigned int)ref.queue) vu_handle_tx(vdev, ref.queue, now);
And here.
}
/** - * vu_send_single() - Send a buffer to the front-end using the RX virtqueue - * @c: execution context + * vu_send_single() - Send a buffer to the front-end using a specified virtqueue + * @c: Execution context + * @qpair: Queue pair on which to send the buffer * @buf: address of the buffer * @size: size of the buffer * * Return: number of bytes sent, -1 if there is an error */ -int vu_send_single(const struct ctx *c, const void *buf, size_t size) +int vu_send_single(const struct ctx *c, unsigned int qpair, const void *buf, size_t size) { struct vu_dev *vdev = c->vdev; - struct vu_virtq *vq = &vdev->vq[VHOST_USER_RX_QUEUE]; struct vu_virtq_element elem[VIRTQUEUE_MAX_SIZE]; struct iovec in_sg[VIRTQUEUE_MAX_SIZE]; + struct vu_virtq *vq; size_t total, in_total; int elem_cnt; int i;
+ vq = &vdev->vq[QPAIR_TOGUEST_QUEUE(qpair)]; + trace("vu_send_single size %zu", size);
if (!vu_queue_enabled(vq) || !vu_queue_started(vq)) { diff --git a/vu_common.h b/vu_common.h index 817384175a1d..f5603d9ddeb6 100644 --- a/vu_common.h +++ b/vu_common.h @@ -23,7 +23,8 @@ void vu_flush(const struct vu_dev *vdev, struct vu_virtq *vq, struct vu_virtq_element *elem, int elem_cnt, size_t frame_len); void vu_kick_cb(struct vu_dev *vdev, union epoll_ref ref, const struct timespec *now); -int vu_send_single(const struct ctx *c, const void *buf, size_t size); +int vu_send_single(const struct ctx *c, unsigned int qpair, const void *buf, + size_t size); void vu_pad(const struct iovec *iov, size_t cnt, size_t frame_len);
#endif /* VU_COMMON_H */ -- 2.54.0
-- David Gibson (he or they) | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you, not the other way | around. http://www.ozlabs.org/~dgibson