Re: [RFC PATCH v5 11/26] vhost: Handle host notifiers in SVQ

If device supports host notifiers, this makes one jump less (kernel) to
deliver SVQ notifications to it.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
  hw/virtio/vhost-shadow-virtqueue.h |  2 ++
  hw/virtio/vhost-shadow-virtqueue.c | 23 ++++++++++++++++++++++-
  2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/hw/virtio/vhost-shadow-virtqueue.h b/hw/virtio/vhost-shadow-virtqueue.h
index 30ab9643b9..eb0a54f954 100644
--- a/hw/virtio/vhost-shadow-virtqueue.h
+++ b/hw/virtio/vhost-shadow-virtqueue.h

@@ -18,6 +18,8 @@ typedef struct VhostShadowVirtqueue VhostShadowVirtqueue;
  void vhost_svq_set_svq_kick_fd(VhostShadowVirtqueue *svq, int svq_kick_fd);
  const EventNotifier *vhost_svq_get_dev_kick_notifier(
                                                const VhostShadowVirtqueue *svq);
+void vhost_svq_set_host_mr_notifier(VhostShadowVirtqueue *svq, void *addr);
+
  void vhost_svq_start(struct vhost_dev *dev, unsigned idx,
                       VhostShadowVirtqueue *svq, int svq_kick_fd);
  void vhost_svq_stop(struct vhost_dev *dev, unsigned idx,

diff --git a/hw/virtio/vhost-shadow-virtqueue.c b/hw/virtio/vhost-shadow-virtqueue.c
index fda60d11db..e3dcc039b6 100644
--- a/hw/virtio/vhost-shadow-virtqueue.c
+++ b/hw/virtio/vhost-shadow-virtqueue.c

@@ -29,6 +29,12 @@ typedef struct VhostShadowVirtqueue {
       * So shadow virtqueue must not clean it, or we would lose VirtQueue one.
       */
      EventNotifier svq_kick;
+
+    /* Device's host notifier memory region. NULL means no region */
+    void *host_notifier_mr;
+
+    /* Virtio queue shadowing */
+    VirtQueue *vq;
  } VhostShadowVirtqueue;
  
  /**

@@ -50,7 +56,20 @@ static void vhost_handle_guest_kick(EventNotifier *n)
          return;
      }
  
-    event_notifier_set(&svq->hdev_kick);
+    if (svq->host_notifier_mr) {
+        uint16_t *mr = svq->host_notifier_mr;
+        *mr = virtio_get_queue_index(svq->vq);

+    } else {
+        event_notifier_set(&svq->hdev_kick);
+    }
+}
+
+/*
+ * Set the device's memory region notifier. addr = NULL clear it.
+ */
+void vhost_svq_set_host_mr_notifier(VhostShadowVirtqueue *svq, void *addr)
+{
+    svq->host_notifier_mr = addr;
  }
  
  /**

@@ -134,6 +153,7 @@ void vhost_svq_stop(struct vhost_dev *dev, unsigned idx,
   */
  VhostShadowVirtqueue *vhost_svq_new(struct vhost_dev *dev, int idx)
  {
+    int vq_idx = dev->vq_index + idx;
      g_autofree VhostShadowVirtqueue *svq = g_new0(VhostShadowVirtqueue, 1);
      int r;
  

@@ -151,6 +171,7 @@ VhostShadowVirtqueue *vhost_svq_new(struct vhost_dev *dev, int idx)
          goto err_init_hdev_call;
      }
  
+    svq->vq = virtio_get_queue(dev->vdev, vq_idx);
      return g_steal_pointer(&svq);
  
  err_init_hdev_call: