vhost: add support for negotiating extended features

Similar to virtio infra, vhost core maintains the features status
in the full extended format and allows the devices to implement
extended version of the getter/setter.

Note that 'protocol_features' are not extended: they are only
used by vhost-user, and the latter device is not going to implement
extended features soon.

Reviewed-by: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>
Acked-by: Jason Wang <jasowang@redhat.com>
Acked-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Tested-by: Lei Yang <leiyang@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Message-ID: <a0062c3b1847fb2baedd6cd8f6ef13b051d6beb2.1758549625.git.pabeni@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

3 files changed, 103 insertions, 27 deletions

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 6557c58d12..5f485ad6cb 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -972,20 +972,34 @@ static int vhost_virtqueue_set_addr(struct vhost_dev *dev,
 static int vhost_dev_set_features(struct vhost_dev *dev,
                                   bool enable_log)
 {
-    uint64_t features = dev->acked_features;
+    uint64_t features[VIRTIO_FEATURES_NU64S];
     int r;
+
+    virtio_features_copy(features, dev->acked_features_ex);
     if (enable_log) {
-        features |= 0x1ULL << VHOST_F_LOG_ALL;
+        virtio_add_feature_ex(features, VHOST_F_LOG_ALL);
     }
     if (!vhost_dev_has_iommu(dev)) {
-        features &= ~(0x1ULL << VIRTIO_F_IOMMU_PLATFORM);
+        virtio_clear_feature_ex(features, VIRTIO_F_IOMMU_PLATFORM);
     }
     if (dev->vhost_ops->vhost_force_iommu) {
         if (dev->vhost_ops->vhost_force_iommu(dev) == true) {
-            features |= 0x1ULL << VIRTIO_F_IOMMU_PLATFORM;
+            virtio_add_feature_ex(features, VIRTIO_F_IOMMU_PLATFORM);
        }
     }
-    r = dev->vhost_ops->vhost_set_features(dev, features);
+
+    if (virtio_features_use_ex(features) &&
+        !dev->vhost_ops->vhost_set_features_ex) {
+        r = -EINVAL;
+        VHOST_OPS_DEBUG(r, "extended features without device support");
+        goto out;
+    }
+
+    if (dev->vhost_ops->vhost_set_features_ex) {
+        r = dev->vhost_ops->vhost_set_features_ex(dev, features);
+    } else {
+        r = dev->vhost_ops->vhost_set_features(dev, features[0]);
+    }
     if (r < 0) {
         VHOST_OPS_DEBUG(r, "vhost_set_features failed");
         goto out;
@@ -1508,12 +1522,27 @@ static void vhost_virtqueue_cleanup(struct vhost_virtqueue *vq)
     }
 }
 
+static int vhost_dev_get_features(struct vhost_dev *hdev,
+                                  uint64_t *features)
+{
+    uint64_t features64;
+    int r;
+
+    if (hdev->vhost_ops->vhost_get_features_ex) {
+        return hdev->vhost_ops->vhost_get_features_ex(hdev, features);
+    }
+
+    r = hdev->vhost_ops->vhost_get_features(hdev, &features64);
+    virtio_features_from_u64(features, features64);
+    return r;
+}
+
 int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
                    VhostBackendType backend_type, uint32_t busyloop_timeout,
                    Error **errp)
 {
+    uint64_t features[VIRTIO_FEATURES_NU64S];
     unsigned int used, reserved, limit;
-    uint64_t features;
     int i, r, n_initialized_vqs = 0;
 
     hdev->vdev = NULL;
@@ -1533,7 +1562,7 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
         goto fail;
     }
 
-    r = hdev->vhost_ops->vhost_get_features(hdev, &features);
+    r = vhost_dev_get_features(hdev, features);
     if (r < 0) {
         error_setg_errno(errp, -r, "vhost_get_features failed");
         goto fail;
@@ -1571,7 +1600,7 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
         }
     }
 
-    hdev->features = features;
+    virtio_features_copy(hdev->features_ex, features);
 
     hdev->memory_listener = (MemoryListener) {
         .name = "vhost",
@@ -1594,7 +1623,7 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
     };
 
     if (hdev->migration_blocker == NULL) {
-        if (!(hdev->features & (0x1ULL << VHOST_F_LOG_ALL))) {
+        if (!virtio_has_feature_ex(hdev->features_ex, VHOST_F_LOG_ALL)) {
             error_setg(&hdev->migration_blocker,
                        "Migration disabled: vhost lacks VHOST_F_LOG_ALL feature.");
         } else if (vhost_dev_log_is_shared(hdev) && !qemu_memfd_alloc_check()) {
@@ -1859,28 +1888,27 @@ static void vhost_start_config_intr(struct vhost_dev *dev)
     }
 }
 
-uint64_t vhost_get_features(struct vhost_dev *hdev, const int *feature_bits,
-                            uint64_t features)
+void vhost_get_features_ex(struct vhost_dev *hdev,
+                           const int *feature_bits,
+                           uint64_t *features)
 {
     const int *bit = feature_bits;
+
     while (*bit != VHOST_INVALID_FEATURE_BIT) {
-        uint64_t bit_mask = (1ULL << *bit);
-        if (!(hdev->features & bit_mask)) {
-            features &= ~bit_mask;
+        if (!virtio_has_feature_ex(hdev->features_ex, *bit)) {
+            virtio_clear_feature_ex(features, *bit);
         }
         bit++;
     }
-    return features;
 }
 
-void vhost_ack_features(struct vhost_dev *hdev, const int *feature_bits,
-                        uint64_t features)
+void vhost_ack_features_ex(struct vhost_dev *hdev, const int *feature_bits,
+                           const uint64_t *features)
 {
     const int *bit = feature_bits;
     while (*bit != VHOST_INVALID_FEATURE_BIT) {
-        uint64_t bit_mask = (1ULL << *bit);
-        if (features & bit_mask) {
-            hdev->acked_features |= bit_mask;
+        if (virtio_has_feature_ex(features, *bit)) {
+            virtio_add_feature_ex(hdev->acked_features_ex, *bit);
         }
         bit++;
     }
diff --git a/include/hw/virtio/vhost-backend.h b/include/hw/virtio/vhost-backend.h
index d6df209a2f..ff94fa1734 100644
--- a/include/hw/virtio/vhost-backend.h
+++ b/include/hw/virtio/vhost-backend.h
@@ -95,6 +95,10 @@ typedef int (*vhost_new_worker_op)(struct vhost_dev *dev,
                                    struct vhost_worker_state *worker);
 typedef int (*vhost_free_worker_op)(struct vhost_dev *dev,
                                     struct vhost_worker_state *worker);
+typedef int (*vhost_set_features_ex_op)(struct vhost_dev *dev,
+                                        const uint64_t *features);
+typedef int (*vhost_get_features_ex_op)(struct vhost_dev *dev,
+                                        uint64_t *features);
 typedef int (*vhost_set_features_op)(struct vhost_dev *dev,
                                      uint64_t features);
 typedef int (*vhost_get_features_op)(struct vhost_dev *dev,
@@ -186,6 +190,8 @@ typedef struct VhostOps {
     vhost_free_worker_op vhost_free_worker;
     vhost_get_vring_worker_op vhost_get_vring_worker;
     vhost_attach_vring_worker_op vhost_attach_vring_worker;
+    vhost_set_features_ex_op vhost_set_features_ex;
+    vhost_get_features_ex_op vhost_get_features_ex;
     vhost_set_features_op vhost_set_features;
     vhost_get_features_op vhost_get_features;
     vhost_set_backend_cap_op vhost_set_backend_cap;
diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
index 66be6afc88..08bbb4dfe9 100644
--- a/include/hw/virtio/vhost.h
+++ b/include/hw/virtio/vhost.h
@@ -107,9 +107,9 @@ struct vhost_dev {
      * future use should be discouraged and the variable retired as
      * its easy to confuse with the VirtIO backend_features.
      */
-    uint64_t features;
-    uint64_t acked_features;
-    uint64_t backend_features;
+    VIRTIO_DECLARE_FEATURES(features);
+    VIRTIO_DECLARE_FEATURES(acked_features);
+    VIRTIO_DECLARE_FEATURES(backend_features);
 
     /**
      * @protocol_features: is the vhost-user only feature set by
@@ -321,6 +321,20 @@ void vhost_virtqueue_mask(struct vhost_dev *hdev, VirtIODevice *vdev, int n,
                           bool mask);
 
 /**
+ * vhost_get_features_ex() - sanitize the extended features set
+ * @hdev: common vhost_dev structure
+ * @feature_bits: pointer to terminated table of feature bits
+ * @features: original features set, filtered out on return
+ *
+ * This is the extended variant of vhost_get_features(), supporting the
+ * the extended features set. Filter it with the intersection of what is
+ * supported by the vhost backend (hdev->features) and the supported
+ * feature_bits.
+ */
+void vhost_get_features_ex(struct vhost_dev *hdev,
+                           const int *feature_bits,
+                           uint64_t *features);
+/**
  * vhost_get_features() - return a sanitised set of feature bits
  * @hdev: common vhost_dev structure
  * @feature_bits: pointer to terminated table of feature bits
@@ -330,8 +344,28 @@ void vhost_virtqueue_mask(struct vhost_dev *hdev, VirtIODevice *vdev, int n,
  * is supported by the vhost backend (hdev->features), the supported
  * feature_bits and the requested feature set.
  */
-uint64_t vhost_get_features(struct vhost_dev *hdev, const int *feature_bits,
-                            uint64_t features);
+static inline uint64_t vhost_get_features(struct vhost_dev *hdev,
+                                          const int *feature_bits,
+                                          uint64_t features)
+{
+    uint64_t features_ex[VIRTIO_FEATURES_NU64S];
+
+    virtio_features_from_u64(features_ex, features);
+    vhost_get_features_ex(hdev, feature_bits, features_ex);
+    return features_ex[0];
+}
+
+/**
+ * vhost_ack_features_ex() - set vhost full set of acked_features
+ * @hdev: common vhost_dev structure
+ * @feature_bits: pointer to terminated table of feature bits
+ * @features: requested feature set
+ *
+ * This sets the internal hdev->acked_features to the intersection of
+ * the backends advertised features and the supported feature_bits.
+ */
+void vhost_ack_features_ex(struct vhost_dev *hdev, const int *feature_bits,
+                           const uint64_t *features);
 
 /**
  * vhost_ack_features() - set vhost acked_features
@@ -342,8 +376,16 @@ uint64_t vhost_get_features(struct vhost_dev *hdev, const int *feature_bits,
  * This sets the internal hdev->acked_features to the intersection of
  * the backends advertised features and the supported feature_bits.
  */
-void vhost_ack_features(struct vhost_dev *hdev, const int *feature_bits,
-                        uint64_t features);
+static inline void vhost_ack_features(struct vhost_dev *hdev,
+                                      const int *feature_bits,
+                                      uint64_t features)
+{
+    uint64_t features_ex[VIRTIO_FEATURES_NU64S];
+
+    virtio_features_from_u64(features_ex, features);
+    vhost_ack_features_ex(hdev, feature_bits, features_ex);
+}
+
 unsigned int vhost_get_max_memslots(void);
 unsigned int vhost_get_free_memslots(void);