Merge branch 'virtio_udp_tunnel_08_07_2025' of https://github.com/pabeni/linux-devel

Paolo Abeni says:

====================
virtio: introduce GSO over UDP tunnel

Some virtualized deployments use UDP tunnel pervasively and are impacted
negatively by the lack of GSO support for such kind of traffic in the
virtual NIC driver.

The virtio_net specification recently introduced support for GSO over
UDP tunnel, this series updates the virtio implementation to support
such a feature.

Currently the kernel virtio support limits the feature space to 64,
while the virtio specification allows for a larger number of features.
Specifically the GSO-over-UDP-tunnel-related virtio features use bits
65-69.

The first four patches in this series rework the virtio and vhost
feature support to cope with up to 128 bits. The limit is set by
a define and could be easily raised in future, as needed.

This implementation choice is aimed at keeping the code churn as
limited as possible. For the same reason, only the virtio_net driver is
reworked to leverage the extended feature space; all other
virtio/vhost drivers are unaffected, but could be upgraded to support
the extended features space in a later time.

The last four patches bring in the actual GSO over UDP tunnel support.
As per specification, some additional fields are introduced into the
virtio net header to support the new offload. The presence of such
fields depends on the negotiated features.

New helpers are introduced to convert the UDP-tunneled skb metadata to
an extended virtio net header and vice versa. Such helpers are used by
the tun and virtio_net driver to cope with the newly supported offloads.

Tested with basic stream transfer with all the possible permutations of
host kernel/qemu/guest kernel with/without GSO over UDP tunnel support.
====================

Link: https://patch.msgid.link/cover.1751874094.git.pabeni@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 75 insertions, 20 deletions

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 9dbd88eb9ff4..bfb774c273ea 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -69,12 +69,14 @@ MODULE_PARM_DESC(experimental_zcopytx, "Enable Zero Copy TX;"
 
 #define VHOST_DMA_IS_DONE(len) ((__force u32)(len) >= (__force u32)VHOST_DMA_DONE_LEN)
 
-enum {
-	VHOST_NET_FEATURES = VHOST_FEATURES |
-			 (1ULL << VHOST_NET_F_VIRTIO_NET_HDR) |
-			 (1ULL << VIRTIO_NET_F_MRG_RXBUF) |
-			 (1ULL << VIRTIO_F_ACCESS_PLATFORM) |
-			 (1ULL << VIRTIO_F_RING_RESET)
+static const u64 vhost_net_features[VIRTIO_FEATURES_DWORDS] = {
+	VHOST_FEATURES |
+	(1ULL << VHOST_NET_F_VIRTIO_NET_HDR) |
+	(1ULL << VIRTIO_NET_F_MRG_RXBUF) |
+	(1ULL << VIRTIO_F_ACCESS_PLATFORM) |
+	(1ULL << VIRTIO_F_RING_RESET),
+	VIRTIO_BIT(VIRTIO_NET_F_GUEST_UDP_TUNNEL_GSO) |
+	VIRTIO_BIT(VIRTIO_NET_F_HOST_UDP_TUNNEL_GSO),
 };
 
 enum {
@@ -1606,16 +1608,23 @@ done:
 	return err;
 }
 
-static int vhost_net_set_features(struct vhost_net *n, u64 features)
+static int vhost_net_set_features(struct vhost_net *n, const u64 *features)
 {
 	size_t vhost_hlen, sock_hlen, hdr_len;
 	int i;
 
-	hdr_len = (features & ((1ULL << VIRTIO_NET_F_MRG_RXBUF) |
-			       (1ULL << VIRTIO_F_VERSION_1))) ?
-			sizeof(struct virtio_net_hdr_mrg_rxbuf) :
-			sizeof(struct virtio_net_hdr);
-	if (features & (1 << VHOST_NET_F_VIRTIO_NET_HDR)) {
+	hdr_len = virtio_features_test_bit(features, VIRTIO_NET_F_MRG_RXBUF) ||
+		  virtio_features_test_bit(features, VIRTIO_F_VERSION_1) ?
+		  sizeof(struct virtio_net_hdr_mrg_rxbuf) :
+		  sizeof(struct virtio_net_hdr);
+
+	if (virtio_features_test_bit(features,
+				     VIRTIO_NET_F_HOST_UDP_TUNNEL_GSO) ||
+	    virtio_features_test_bit(features,
+				     VIRTIO_NET_F_GUEST_UDP_TUNNEL_GSO))
+		hdr_len = sizeof(struct virtio_net_hdr_v1_hash_tunnel);
+
+	if (virtio_features_test_bit(features, VHOST_NET_F_VIRTIO_NET_HDR)) {
 		/* vhost provides vnet_hdr */
 		vhost_hlen = hdr_len;
 		sock_hlen = 0;
@@ -1625,18 +1634,19 @@ static int vhost_net_set_features(struct vhost_net *n, u64 features)
 		sock_hlen = hdr_len;
 	}
 	mutex_lock(&n->dev.mutex);
-	if ((features & (1 << VHOST_F_LOG_ALL)) &&
+	if (virtio_features_test_bit(features, VHOST_F_LOG_ALL) &&
 	    !vhost_log_access_ok(&n->dev))
 		goto out_unlock;
 
-	if ((features & (1ULL << VIRTIO_F_ACCESS_PLATFORM))) {
+	if (virtio_features_test_bit(features, VIRTIO_F_ACCESS_PLATFORM)) {
 		if (vhost_init_device_iotlb(&n->dev))
 			goto out_unlock;
 	}
 
 	for (i = 0; i < VHOST_NET_VQ_MAX; ++i) {
 		mutex_lock(&n->vqs[i].vq.mutex);
-		n->vqs[i].vq.acked_features = features;
+		virtio_features_copy(n->vqs[i].vq.acked_features_array,
+				     features);
 		n->vqs[i].vhost_hlen = vhost_hlen;
 		n->vqs[i].sock_hlen = sock_hlen;
 		mutex_unlock(&n->vqs[i].vq.mutex);
@@ -1673,12 +1683,13 @@ out:
 static long vhost_net_ioctl(struct file *f, unsigned int ioctl,
 			    unsigned long arg)
 {
+	u64 all_features[VIRTIO_FEATURES_DWORDS];
 	struct vhost_net *n = f->private_data;
 	void __user *argp = (void __user *)arg;
 	u64 __user *featurep = argp;
 	struct vhost_vring_file backend;
-	u64 features;
-	int r;
+	u64 features, count, copied;
+	int r, i;
 
 	switch (ioctl) {
 	case VHOST_NET_SET_BACKEND:
@@ -1686,16 +1697,60 @@ static long vhost_net_ioctl(struct file *f, unsigned int ioctl,
 			return -EFAULT;
 		return vhost_net_set_backend(n, backend.index, backend.fd);
 	case VHOST_GET_FEATURES:
-		features = VHOST_NET_FEATURES;
+		features = vhost_net_features[0];
 		if (copy_to_user(featurep, &features, sizeof features))
 			return -EFAULT;
 		return 0;
 	case VHOST_SET_FEATURES:
 		if (copy_from_user(&features, featurep, sizeof features))
 			return -EFAULT;
-		if (features & ~VHOST_NET_FEATURES)
+		if (features & ~vhost_net_features[0])
 			return -EOPNOTSUPP;
-		return vhost_net_set_features(n, features);
+
+		virtio_features_from_u64(all_features, features);
+		return vhost_net_set_features(n, all_features);
+	case VHOST_GET_FEATURES_ARRAY:
+		if (copy_from_user(&count, featurep, sizeof(count)))
+			return -EFAULT;
+
+		/* Copy the net features, up to the user-provided buffer size */
+		argp += sizeof(u64);
+		copied = min(count, VIRTIO_FEATURES_DWORDS);
+		if (copy_to_user(argp, vhost_net_features,
+				 copied * sizeof(u64)))
+			return -EFAULT;
+
+		/* Zero the trailing space provided by user-space, if any */
+		if (clear_user(argp, size_mul(count - copied, sizeof(u64))))
+			return -EFAULT;
+		return 0;
+	case VHOST_SET_FEATURES_ARRAY:
+		if (copy_from_user(&count, featurep, sizeof(count)))
+			return -EFAULT;
+
+		virtio_features_zero(all_features);
+		argp += sizeof(u64);
+		copied = min(count, VIRTIO_FEATURES_DWORDS);
+		if (copy_from_user(all_features, argp, copied * sizeof(u64)))
+			return -EFAULT;
+
+		/*
+		 * Any feature specified by user-space above
+		 * VIRTIO_FEATURES_MAX is not supported by definition.
+		 */
+		for (i = copied; i < count; ++i) {
+			if (copy_from_user(&features, featurep + 1 + i,
+					   sizeof(features)))
+				return -EFAULT;
+			if (features)
+				return -EOPNOTSUPP;
+		}
+
+		for (i = 0; i < VIRTIO_FEATURES_DWORDS; i++)
+			if (all_features[i] & ~vhost_net_features[i])
+				return -EOPNOTSUPP;
+
+		return vhost_net_set_features(n, all_features);
 	case VHOST_GET_BACKEND_FEATURES:
 		features = VHOST_NET_BACKEND_FEATURES;
 		if (copy_to_user(featurep, &features, sizeof(features)))