[PATCH v6 08/14] vhost: add support for negotiating extended features

[Paolo Abeni <pabeni@redhat.com>]

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>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
v3 -> v4:
  - fix compile warning for real :(
  - de-duplicate code from vhost_{get,ack}_features and
    vhost_{get,ack}_features_ex
  - use new virtio_features macro names

v2 -> v3:
  - fix compile warning
  - _array -> _ex

v1 -> v2:
  - uint128_t -> uint64_t[]
  - add _ex() variant of features manipulation helpers
---
 hw/virtio/vhost.c                 | 68 ++++++++++++++++++++++---------
 include/hw/virtio/vhost-backend.h |  6 +++
 include/hw/virtio/vhost.h         | 56 +++++++++++++++++++++----
 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
@@ -320,6 +320,20 @@ bool vhost_virtqueue_pending(struct vhost_dev *hdev, int n);
 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
@@ -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);
 
-- 
2.51.0