Use the extended feature type for 'acked_features' and implement
two new ioctls operation allowing the user-space to set/query an
unbounded amount of features.

The actual number of processed features is limited by VIRTIO_FEATURES_MAX
and attempts to set features above such limit fail with
EOPNOTSUPP.

Note that: the legacy ioctls implicitly truncate the negotiated
features to the lower 64 bits range and the 'acked_backend_features'
field don't need conversion, as the only negotiated feature there
is in the low 64 bit range.

Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
v3 -> v4:
   - use a single static (lower case) constant instead of enum and old def
   - simpler VHOST_GET_FEATURES_ARRAY impl
   - avoid using virtio_features_and_not

v2 -> v3:
   - virtio_features_t -> u64[2]
   - add __counted_by annotation to vhost_features_array

v1 -> v2:
   - change the ioctl to use an extensible API
---
  drivers/vhost/net.c              | 87 ++++++++++++++++++++++++--------
  drivers/vhost/vhost.c            |  2 +-
  drivers/vhost/vhost.h            |  4 +-
  include/uapi/linux/vhost.h       |  7 +++
  include/uapi/linux/vhost_types.h |  5 ++
  5 files changed, 82 insertions(+), 23 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 7cbfc7d718b3..126aa4ee26a8 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c

@@ -69,12 +69,12 @@ 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),
  };
  
  enum {

@@ -1614,16 +1614,17 @@ static long vhost_net_reset_owner(struct vhost_net *n)
  	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, VHOST_NET_F_VIRTIO_NET_HDR)) {
  		/* vhost provides vnet_hdr */
  		vhost_hlen = hdr_len;
  		sock_hlen = 0;

@@ -1633,18 +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);

@@ -1681,12 +1683,13 @@ static long vhost_net_set_owner(struct vhost_net *n)
  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:

@@ -1694,16 +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, argp, sizeof(u64)))
+			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, (count - copied) * sizeof(u64)))
+			return -EFAULT;
+		return 0;
+	case VHOST_SET_FEATURES_ARRAY:
+		if (copy_from_user(&count, argp, sizeof(u64)))
+			return -EFAULT;
+
+		virtio_features_zero(all_features);
+		for (i = 0; i < min(count, VIRTIO_FEATURES_DWORDS); ++i) {
+			argp += sizeof(u64);
+			if (copy_from_user(&all_features[i], argp,
+					   sizeof(u64)))
+				return -EFAULT;
+		}

+			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)))

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 3a5ebb973dba..1094256a943c 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c

@@ -372,7 +372,7 @@ static void vhost_vq_reset(struct vhost_dev *dev,
  	vq->log_used = false;
  	vq->log_addr = -1ull;
  	vq->private_data = NULL;
-	vq->acked_features = 0;
+	virtio_features_zero(vq->acked_features_array);
  	vq->acked_backend_features = 0;
  	vq->log_base = NULL;
  	vq->error_ctx = NULL;

diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index bb75a292d50c..d1aed35c4b07 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h

@@ -133,7 +133,7 @@ struct vhost_virtqueue {
  	struct vhost_iotlb *umem;
  	struct vhost_iotlb *iotlb;
  	void *private_data;
-	u64 acked_features;
+	VIRTIO_DECLARE_FEATURES(acked_features);
  	u64 acked_backend_features;
  	/* Log write descriptors */
  	void __user *log_base;

@@ -291,7 +291,7 @@ static inline void *vhost_vq_get_backend(struct vhost_virtqueue *vq)
  
  static inline bool vhost_has_feature(struct vhost_virtqueue *vq, int bit)
  {
-	return vq->acked_features & (1ULL << bit);
+	return virtio_features_test_bit(vq->acked_features_array, bit);
  }
  
  static inline bool vhost_backend_has_feature(struct vhost_virtqueue *vq, int bit)

diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
index d4b3e2ae1314..d6ad01fbb8d2 100644
--- a/include/uapi/linux/vhost.h
+++ b/include/uapi/linux/vhost.h

@@ -235,4 +235,11 @@
   */
  #define VHOST_VDPA_GET_VRING_SIZE	_IOWR(VHOST_VIRTIO, 0x82,	\
  					      struct vhost_vring_state)
+
+/* Extended features manipulation */
+#define VHOST_GET_FEATURES_ARRAY _IOR(VHOST_VIRTIO, 0x83, \
+				       struct vhost_features_array)
+#define VHOST_SET_FEATURES_ARRAY _IOW(VHOST_VIRTIO, 0x83, \
+				       struct vhost_features_array)
+
  #endif

diff --git a/include/uapi/linux/vhost_types.h b/include/uapi/linux/vhost_types.h
index d7656908f730..1c39cc5f5a31 100644
--- a/include/uapi/linux/vhost_types.h
+++ b/include/uapi/linux/vhost_types.h

@@ -110,6 +110,11 @@ struct vhost_msg_v2 {
  	};
  };
  
+struct vhost_features_array {
+	__u64 count; /* number of entries present in features array */
+	__u64 features[] __counted_by(count);
+};
+
  struct vhost_memory_region {
  	__u64 guest_phys_addr;
  	__u64 memory_size; /* bytes */