[PATCH 0/3] This series contains fixes and improvements to the vhost-user implementation

[PATCH 0/3] This series contains fixes and improvements to the vhost-user implementation

[Laurent Vivier]

The first patch fixes a protocol compliance issue where VHOST_USER_GET_QUEUE_NUM
was incorrectly returning the number of virtqueues instead of queue pairs. The
vhost-user specification clearly states this should return the maximum number
of queues supported by the backend. Since each queue consists of an RX/TX pair,
the correct value is VHOST_USER_MAX_VQS / 2. This patch also renames the
constant to better reflect its meaning.

The second and third patches address virtqueue handling in the UDP and TCP
receive paths. These changes pass the virtqueue pointer explicitly to the
receive functions, enabling proper queue selection for future multiqueue
support. This ensures packets are processed on the same virtqueue as the
caller.

These changes lay the groundwork for full multiqueue support while fixing
existing protocol compliance issues.

Laurent Vivier (3):
  vhost-user: Fix VHOST_USER_GET_QUEUE_NUM to return number of queues
  udp_vu: Pass virtqueue pointer to udp_vu_sock_recv()
  tcp_vu: Pass virtqueue pointer to tcp_vu_sock_recv()

 tcp_vu.c     |  8 ++++----
 udp_vu.c     |  9 +++++----
 vhost_user.c | 16 +++++++++-------
 virtio.h     |  4 ++--
 4 files changed, 20 insertions(+), 17 deletions(-)

-- 
2.50.1

[PATCH 1/3] vhost-user: Fix VHOST_USER_GET_QUEUE_NUM to return number of queues

[Laurent Vivier]

The vhost-user specification states that VHOST_USER_GET_QUEUE_NUM should
return the maximum number of queues supported by the back-end, not the
number of virtqueues. Since each queue pair consists of RX and TX
virtqueues, we need to divide VHOST_USER_MAX_QUEUES by 2 to get the
correct queue count.

Also rename VHOST_USER_MAX_QUEUES to VHOST_USER_MAX_VQS throughout the
codebase to better reflect that it represents the maximum number of
virtqueues, not queue pairs.

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
---
 vhost_user.c | 16 +++++++++-------
 virtio.h     |  4 ++--
 2 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/vhost_user.c b/vhost_user.c
index f97ec6064cac..fa343a86fac2 100644
--- a/vhost_user.c
+++ b/vhost_user.c
@@ -345,7 +345,7 @@ static void vu_set_enable_all_rings(struct vu_dev *vdev, bool enable)
 {
 	uint16_t i;
 
-	for (i = 0; i < VHOST_USER_MAX_QUEUES; i++)
+	for (i = 0; i < VHOST_USER_MAX_VQS; i++)
 		vdev->vq[i].enable = enable;
 }
 
@@ -477,7 +477,7 @@ static bool vu_set_mem_table_exec(struct vu_dev *vdev,
 		close(vmsg->fds[i]);
 	}
 
-	for (i = 0; i < VHOST_USER_MAX_QUEUES; i++) {
+	for (i = 0; i < VHOST_USER_MAX_VQS; i++) {
 		if (vdev->vq[i].vring.desc) {
 			if (map_ring(vdev, &vdev->vq[i]))
 				die("remapping queue %d during setmemtable", i);
@@ -770,7 +770,7 @@ static void vu_check_queue_msg_file(struct vhost_user_msg *vmsg)
 	bool nofd = vmsg->payload.u64 & VHOST_USER_VRING_NOFD_MASK;
 	int idx = vmsg->payload.u64 & VHOST_USER_VRING_IDX_MASK;
 
-	if (idx >= VHOST_USER_MAX_QUEUES)
+	if (idx >= VHOST_USER_MAX_VQS)
 		die("Invalid vhost-user queue index: %u", idx);
 
 	if (nofd) {
@@ -939,7 +939,9 @@ static bool vu_get_queue_num_exec(struct vu_dev *vdev,
 {
 	(void)vdev;
 
-	vmsg_set_reply_u64(vmsg, VHOST_USER_MAX_QUEUES);
+	vmsg_set_reply_u64(vmsg, VHOST_USER_MAX_VQS / 2);
+
+	debug("VHOST_USER_MAX_VQS  %u", VHOST_USER_MAX_VQS / 2);
 
 	return true;
 }
@@ -960,7 +962,7 @@ static bool vu_set_vring_enable_exec(struct vu_dev *vdev,
 	debug("State.index:  %u", idx);
 	debug("State.enable: %u", enable);
 
-	if (idx >= VHOST_USER_MAX_QUEUES)
+	if (idx >= VHOST_USER_MAX_VQS)
 		die("Invalid vring_enable index: %u", idx);
 
 	vdev->vq[idx].enable = enable;
@@ -1052,7 +1054,7 @@ void vu_init(struct ctx *c)
 
 	c->vdev = &vdev_storage;
 	c->vdev->context = c;
-	for (i = 0; i < VHOST_USER_MAX_QUEUES; i++) {
+	for (i = 0; i < VHOST_USER_MAX_VQS; i++) {
 		c->vdev->vq[i] = (struct vu_virtq){
 			.call_fd = -1,
 			.kick_fd = -1,
@@ -1075,7 +1077,7 @@ void vu_cleanup(struct vu_dev *vdev)
 {
 	unsigned int i;
 
-	for (i = 0; i < VHOST_USER_MAX_QUEUES; i++) {
+	for (i = 0; i < VHOST_USER_MAX_VQS; i++) {
 		struct vu_virtq *vq = &vdev->vq[i];
 
 		vq->started = false;
diff --git a/virtio.h b/virtio.h
index b55cc4042521..12caaa0b6def 100644
--- a/virtio.h
+++ b/virtio.h
@@ -88,7 +88,7 @@ struct vu_dev_region {
 	uint64_t mmap_addr;
 };
 
-#define VHOST_USER_MAX_QUEUES 2
+#define VHOST_USER_MAX_VQS 2
 
 /*
  * Set a reasonable maximum number of ram slots, which will be supported by
@@ -121,7 +121,7 @@ struct vdev_memory {
 struct vu_dev {
 	struct ctx *context;
 	struct vdev_memory memory;
-	struct vu_virtq vq[VHOST_USER_MAX_QUEUES];
+	struct vu_virtq vq[VHOST_USER_MAX_VQS];
 	uint64_t features;
 	uint64_t protocol_features;
 	int log_call_fd;
-- 
2.50.1

Re: [PATCH 1/3] vhost-user: Fix VHOST_USER_GET_QUEUE_NUM to return number of queues

[David Gibson]

[-- Attachment #1: Type: text/plain, Size: 4001 bytes --]

On Fri, Sep 05, 2025 at 05:49:33PM +0200, Laurent Vivier wrote:
> The vhost-user specification states that VHOST_USER_GET_QUEUE_NUM should
> return the maximum number of queues supported by the back-end, not the
> number of virtqueues. Since each queue pair consists of RX and TX
> virtqueues, we need to divide VHOST_USER_MAX_QUEUES by 2 to get the
> correct queue count.
> 
> Also rename VHOST_USER_MAX_QUEUES to VHOST_USER_MAX_VQS throughout the
> codebase to better reflect that it represents the maximum number of
> virtqueues, not queue pairs.
> 
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
>  vhost_user.c | 16 +++++++++-------
>  virtio.h     |  4 ++--
>  2 files changed, 11 insertions(+), 9 deletions(-)
> 
> diff --git a/vhost_user.c b/vhost_user.c
> index f97ec6064cac..fa343a86fac2 100644
> --- a/vhost_user.c
> +++ b/vhost_user.c
> @@ -345,7 +345,7 @@ static void vu_set_enable_all_rings(struct vu_dev *vdev, bool enable)
>  {
>  	uint16_t i;
>  
> -	for (i = 0; i < VHOST_USER_MAX_QUEUES; i++)
> +	for (i = 0; i < VHOST_USER_MAX_VQS; i++)
>  		vdev->vq[i].enable = enable;
>  }
>  
> @@ -477,7 +477,7 @@ static bool vu_set_mem_table_exec(struct vu_dev *vdev,
>  		close(vmsg->fds[i]);
>  	}
>  
> -	for (i = 0; i < VHOST_USER_MAX_QUEUES; i++) {
> +	for (i = 0; i < VHOST_USER_MAX_VQS; i++) {
>  		if (vdev->vq[i].vring.desc) {
>  			if (map_ring(vdev, &vdev->vq[i]))
>  				die("remapping queue %d during setmemtable", i);
> @@ -770,7 +770,7 @@ static void vu_check_queue_msg_file(struct vhost_user_msg *vmsg)
>  	bool nofd = vmsg->payload.u64 & VHOST_USER_VRING_NOFD_MASK;
>  	int idx = vmsg->payload.u64 & VHOST_USER_VRING_IDX_MASK;
>  
> -	if (idx >= VHOST_USER_MAX_QUEUES)
> +	if (idx >= VHOST_USER_MAX_VQS)
>  		die("Invalid vhost-user queue index: %u", idx);
>  
>  	if (nofd) {
> @@ -939,7 +939,9 @@ static bool vu_get_queue_num_exec(struct vu_dev *vdev,
>  {
>  	(void)vdev;
>  
> -	vmsg_set_reply_u64(vmsg, VHOST_USER_MAX_QUEUES);
> +	vmsg_set_reply_u64(vmsg, VHOST_USER_MAX_VQS / 2);
> +
> +	debug("VHOST_USER_MAX_VQS  %u", VHOST_USER_MAX_VQS / 2);
>  
>  	return true;
>  }
> @@ -960,7 +962,7 @@ static bool vu_set_vring_enable_exec(struct vu_dev *vdev,
>  	debug("State.index:  %u", idx);
>  	debug("State.enable: %u", enable);
>  
> -	if (idx >= VHOST_USER_MAX_QUEUES)
> +	if (idx >= VHOST_USER_MAX_VQS)
>  		die("Invalid vring_enable index: %u", idx);
>  
>  	vdev->vq[idx].enable = enable;
> @@ -1052,7 +1054,7 @@ void vu_init(struct ctx *c)
>  
>  	c->vdev = &vdev_storage;
>  	c->vdev->context = c;
> -	for (i = 0; i < VHOST_USER_MAX_QUEUES; i++) {
> +	for (i = 0; i < VHOST_USER_MAX_VQS; i++) {
>  		c->vdev->vq[i] = (struct vu_virtq){
>  			.call_fd = -1,
>  			.kick_fd = -1,
> @@ -1075,7 +1077,7 @@ void vu_cleanup(struct vu_dev *vdev)
>  {
>  	unsigned int i;
>  
> -	for (i = 0; i < VHOST_USER_MAX_QUEUES; i++) {
> +	for (i = 0; i < VHOST_USER_MAX_VQS; i++) {
>  		struct vu_virtq *vq = &vdev->vq[i];
>  
>  		vq->started = false;
> diff --git a/virtio.h b/virtio.h
> index b55cc4042521..12caaa0b6def 100644
> --- a/virtio.h
> +++ b/virtio.h
> @@ -88,7 +88,7 @@ struct vu_dev_region {
>  	uint64_t mmap_addr;
>  };
>  
> -#define VHOST_USER_MAX_QUEUES 2
> +#define VHOST_USER_MAX_VQS 2
>  
>  /*
>   * Set a reasonable maximum number of ram slots, which will be supported by
> @@ -121,7 +121,7 @@ struct vdev_memory {
>  struct vu_dev {
>  	struct ctx *context;
>  	struct vdev_memory memory;
> -	struct vu_virtq vq[VHOST_USER_MAX_QUEUES];
> +	struct vu_virtq vq[VHOST_USER_MAX_VQS];
>  	uint64_t features;
>  	uint64_t protocol_features;
>  	int log_call_fd;
> -- 
> 2.50.1
> 

-- 
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

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[PATCH 2/3] udp_vu: Pass virtqueue pointer to udp_vu_sock_recv()

[Laurent Vivier]

Pass the virtqueue pointer to udp_vu_sock_recv() to enable proper
queue selection for multiqueue support. This ensures that received
packets are processed on the same virtqueue as the caller.

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
---
 udp_vu.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/udp_vu.c b/udp_vu.c
index 2fb7b900ca31..099677f914e7 100644
--- a/udp_vu.c
+++ b/udp_vu.c
@@ -60,16 +60,17 @@ static size_t udp_vu_hdrlen(bool v6)
 /**
  * udp_vu_sock_recv() - Receive datagrams from socket into vhost-user buffers
  * @c:		Execution context
+ * @vq:		virtqueue to use to receive data
  * @s:		Socket to receive from
  * @v6:		Set for IPv6 connections
  * @dlen:	Size of received data (output)
  *
  * Return: number of iov entries used to store the datagram
  */
-static int udp_vu_sock_recv(const struct ctx *c, int s, bool v6, ssize_t *dlen)
+static int udp_vu_sock_recv(const struct ctx *c, struct vu_virtq *vq, int s,
+			    bool v6, ssize_t *dlen)
 {
-	struct vu_dev *vdev = c->vdev;
-	struct vu_virtq *vq = &vdev->vq[VHOST_USER_RX_QUEUE];
+	const struct vu_dev *vdev = c->vdev;
 	int iov_cnt, idx, iov_used;
 	struct msghdr msg  = { 0 };
 	size_t off, hdrlen;
@@ -210,7 +211,7 @@ void udp_vu_sock_to_tap(const struct ctx *c, int s, int n, flow_sidx_t tosidx)
 		ssize_t dlen;
 		int iov_used;
 
-		iov_used = udp_vu_sock_recv(c, s, v6, &dlen);
+		iov_used = udp_vu_sock_recv(c, vq, s, v6, &dlen);
 		if (iov_used <= 0)
 			break;
 
-- 
2.50.1

Re: [PATCH 2/3] udp_vu: Pass virtqueue pointer to udp_vu_sock_recv()

[David Gibson]

[-- Attachment #1: Type: text/plain, Size: 2054 bytes --]

On Fri, Sep 05, 2025 at 05:49:34PM +0200, Laurent Vivier wrote:
> Pass the virtqueue pointer to udp_vu_sock_recv() to enable proper
> queue selection for multiqueue support. This ensures that received
> packets are processed on the same virtqueue as the caller.
> 
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

Regardless of future plans, I think it's cleaner to pass the vq than
to rederive it.

> ---
>  udp_vu.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/udp_vu.c b/udp_vu.c
> index 2fb7b900ca31..099677f914e7 100644
> --- a/udp_vu.c
> +++ b/udp_vu.c
> @@ -60,16 +60,17 @@ static size_t udp_vu_hdrlen(bool v6)
>  /**
>   * udp_vu_sock_recv() - Receive datagrams from socket into vhost-user buffers
>   * @c:		Execution context
> + * @vq:		virtqueue to use to receive data
>   * @s:		Socket to receive from
>   * @v6:		Set for IPv6 connections
>   * @dlen:	Size of received data (output)
>   *
>   * Return: number of iov entries used to store the datagram
>   */
> -static int udp_vu_sock_recv(const struct ctx *c, int s, bool v6, ssize_t *dlen)
> +static int udp_vu_sock_recv(const struct ctx *c, struct vu_virtq *vq, int s,
> +			    bool v6, ssize_t *dlen)
>  {
> -	struct vu_dev *vdev = c->vdev;
> -	struct vu_virtq *vq = &vdev->vq[VHOST_USER_RX_QUEUE];
> +	const struct vu_dev *vdev = c->vdev;
>  	int iov_cnt, idx, iov_used;
>  	struct msghdr msg  = { 0 };
>  	size_t off, hdrlen;
> @@ -210,7 +211,7 @@ void udp_vu_sock_to_tap(const struct ctx *c, int s, int n, flow_sidx_t tosidx)
>  		ssize_t dlen;
>  		int iov_used;
>  
> -		iov_used = udp_vu_sock_recv(c, s, v6, &dlen);
> +		iov_used = udp_vu_sock_recv(c, vq, s, v6, &dlen);
>  		if (iov_used <= 0)
>  			break;
>  
> -- 
> 2.50.1
> 

-- 
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

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[PATCH 3/3] tcp_vu: Pass virtqueue pointer to tcp_vu_sock_recv()

[Laurent Vivier]

Pass the virtqueue pointer to tcp_vu_sock_recv() to enable proper
queue selection for multiqueue support. This ensures that received
packets are processed on the same virtqueue as the caller.

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
---
 tcp_vu.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/tcp_vu.c b/tcp_vu.c
index cb39bc20355b..c6b5b91ec266 100644
--- a/tcp_vu.c
+++ b/tcp_vu.c
@@ -171,6 +171,7 @@ int tcp_vu_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags)
 
 /** tcp_vu_sock_recv() - Receive datastream from socket into vhost-user buffers
  * @c:			Execution context
+ * @vq:			virtqueue to use to receive data
  * @conn:		Connection pointer
  * @v6:			Set for IPv6 connections
  * @already_sent:	Number of bytes already sent
@@ -181,13 +182,12 @@ int tcp_vu_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags)
  * Return: number of bytes received from the socket, or a negative error code
  * on failure.
  */
-static ssize_t tcp_vu_sock_recv(const struct ctx *c,
+static ssize_t tcp_vu_sock_recv(const struct ctx *c, struct vu_virtq *vq,
 				const struct tcp_tap_conn *conn, bool v6,
 				uint32_t already_sent, size_t fillsize,
 				int *iov_cnt, int *head_cnt)
 {
-	struct vu_dev *vdev = c->vdev;
-	struct vu_virtq *vq = &vdev->vq[VHOST_USER_RX_QUEUE];
+	const struct vu_dev *vdev = c->vdev;
 	struct msghdr mh_sock = { 0 };
 	uint16_t mss = MSS_GET(conn);
 	int s = conn->sock;
@@ -398,7 +398,7 @@ int tcp_vu_data_from_sock(const struct ctx *c, struct tcp_tap_conn *conn)
 	/* collect the buffers from vhost-user and fill them with the
 	 * data from the socket
 	 */
-	len = tcp_vu_sock_recv(c, conn, v6, already_sent, fillsize,
+	len = tcp_vu_sock_recv(c, vq, conn, v6, already_sent, fillsize,
 			       &iov_cnt, &head_cnt);
 	if (len < 0) {
 		if (len != -EAGAIN && len != -EWOULDBLOCK) {
-- 
2.50.1

Re: [PATCH 3/3] tcp_vu: Pass virtqueue pointer to tcp_vu_sock_recv()

[David Gibson]

[-- Attachment #1: Type: text/plain, Size: 2368 bytes --]

On Fri, Sep 05, 2025 at 05:49:35PM +0200, Laurent Vivier wrote:
> Pass the virtqueue pointer to tcp_vu_sock_recv() to enable proper
> queue selection for multiqueue support. This ensures that received
> packets are processed on the same virtqueue as the caller.
> 
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
>  tcp_vu.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/tcp_vu.c b/tcp_vu.c
> index cb39bc20355b..c6b5b91ec266 100644
> --- a/tcp_vu.c
> +++ b/tcp_vu.c
> @@ -171,6 +171,7 @@ int tcp_vu_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags)
>  
>  /** tcp_vu_sock_recv() - Receive datastream from socket into vhost-user buffers
>   * @c:			Execution context
> + * @vq:			virtqueue to use to receive data
>   * @conn:		Connection pointer
>   * @v6:			Set for IPv6 connections
>   * @already_sent:	Number of bytes already sent
> @@ -181,13 +182,12 @@ int tcp_vu_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags)
>   * Return: number of bytes received from the socket, or a negative error code
>   * on failure.
>   */
> -static ssize_t tcp_vu_sock_recv(const struct ctx *c,
> +static ssize_t tcp_vu_sock_recv(const struct ctx *c, struct vu_virtq *vq,
>  				const struct tcp_tap_conn *conn, bool v6,
>  				uint32_t already_sent, size_t fillsize,
>  				int *iov_cnt, int *head_cnt)
>  {
> -	struct vu_dev *vdev = c->vdev;
> -	struct vu_virtq *vq = &vdev->vq[VHOST_USER_RX_QUEUE];
> +	const struct vu_dev *vdev = c->vdev;
>  	struct msghdr mh_sock = { 0 };
>  	uint16_t mss = MSS_GET(conn);
>  	int s = conn->sock;
> @@ -398,7 +398,7 @@ int tcp_vu_data_from_sock(const struct ctx *c, struct tcp_tap_conn *conn)
>  	/* collect the buffers from vhost-user and fill them with the
>  	 * data from the socket
>  	 */
> -	len = tcp_vu_sock_recv(c, conn, v6, already_sent, fillsize,
> +	len = tcp_vu_sock_recv(c, vq, conn, v6, already_sent, fillsize,
>  			       &iov_cnt, &head_cnt);
>  	if (len < 0) {
>  		if (len != -EAGAIN && len != -EWOULDBLOCK) {
> -- 
> 2.50.1
> 

-- 
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

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Re: [PATCH 0/3] This series contains fixes and improvements to the vhost-user implementation

[Stefano Brivio]

On Fri,  5 Sep 2025 17:49:32 +0200
Laurent Vivier <lvivier@redhat.com> wrote:

> The first patch fixes a protocol compliance issue where VHOST_USER_GET_QUEUE_NUM
> was incorrectly returning the number of virtqueues instead of queue pairs. The
> vhost-user specification clearly states this should return the maximum number
> of queues supported by the backend. Since each queue consists of an RX/TX pair,
> the correct value is VHOST_USER_MAX_VQS / 2. This patch also renames the
> constant to better reflect its meaning.
> 
> The second and third patches address virtqueue handling in the UDP and TCP
> receive paths. These changes pass the virtqueue pointer explicitly to the
> receive functions, enabling proper queue selection for future multiqueue
> support. This ensures packets are processed on the same virtqueue as the
> caller.
> 
> These changes lay the groundwork for full multiqueue support while fixing
> existing protocol compliance issues.
> 
> Laurent Vivier (3):
>   vhost-user: Fix VHOST_USER_GET_QUEUE_NUM to return number of queues
>   udp_vu: Pass virtqueue pointer to udp_vu_sock_recv()
>   tcp_vu: Pass virtqueue pointer to tcp_vu_sock_recv()

Applied.

-- 
Stefano