vhost-vdpa: map virtqueue notification area if possible

This patch implements the vq notification mapping support for
vhost-vDPA. This is simply done by using mmap()/munmap() for the
vhost-vDPA fd during device start/stop. For the device without
notification mapping support, we fall back to eventfd based
notification gracefully.

Reviewed-by: Si-Wei Liu <si-wei.liu@oracle.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>

hw/virtio/vhost-vdpa.c

@@ -286,12 +286,95 @@ static int vhost_vdpa_init(struct vhost_dev *dev, void *opaque)
     return 0;
 }
 
+static void vhost_vdpa_host_notifier_uninit(struct vhost_dev *dev,
+                                            int queue_index)
+{
+    size_t page_size = qemu_real_host_page_size;
+    struct vhost_vdpa *v = dev->opaque;
+    VirtIODevice *vdev = dev->vdev;
+    VhostVDPAHostNotifier *n;
+
+    n = &v->notifier[queue_index];
+
+    if (n->addr) {
+        virtio_queue_set_host_notifier_mr(vdev, queue_index, &n->mr, false);
+        object_unparent(OBJECT(&n->mr));
+        munmap(n->addr, page_size);
+        n->addr = NULL;
+    }
+}
+
+static void vhost_vdpa_host_notifiers_uninit(struct vhost_dev *dev, int n)
+{
+    int i;
+
+    for (i = 0; i < n; i++) {
+        vhost_vdpa_host_notifier_uninit(dev, i);
+    }
+}
+
+static int vhost_vdpa_host_notifier_init(struct vhost_dev *dev, int queue_index)
+{
+    size_t page_size = qemu_real_host_page_size;
+    struct vhost_vdpa *v = dev->opaque;
+    VirtIODevice *vdev = dev->vdev;
+    VhostVDPAHostNotifier *n;
+    int fd = v->device_fd;
+    void *addr;
+    char *name;
+
+    vhost_vdpa_host_notifier_uninit(dev, queue_index);
+
+    n = &v->notifier[queue_index];
+
+    addr = mmap(NULL, page_size, PROT_WRITE, MAP_SHARED, fd,
+                queue_index * page_size);
+    if (addr == MAP_FAILED) {
+        goto err;
+    }
+
+    name = g_strdup_printf("vhost-vdpa/host-notifier@%p mmaps[%d]",
+                           v, queue_index);
+    memory_region_init_ram_device_ptr(&n->mr, OBJECT(vdev), name,
+                                      page_size, addr);
+    g_free(name);
+
+    if (virtio_queue_set_host_notifier_mr(vdev, queue_index, &n->mr, true)) {
+        munmap(addr, page_size);
+        goto err;
+    }
+    n->addr = addr;
+
+    return 0;
+
+err:
+    return -1;
+}
+
+static void vhost_vdpa_host_notifiers_init(struct vhost_dev *dev)
+{
+    int i;
+
+    for (i = dev->vq_index; i < dev->vq_index + dev->nvqs; i++) {
+        if (vhost_vdpa_host_notifier_init(dev, i)) {
+            goto err;
+        }
+    }
+
+    return;
+
+err:
+    vhost_vdpa_host_notifiers_uninit(dev, i);
+    return;
+}
+
 static int vhost_vdpa_cleanup(struct vhost_dev *dev)
 {
     struct vhost_vdpa *v;
     assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_VDPA);
     v = dev->opaque;
     trace_vhost_vdpa_cleanup(dev, v);
+    vhost_vdpa_host_notifiers_uninit(dev, dev->nvqs);
     memory_listener_unregister(&v->listener);
 
     dev->opaque = NULL;
@@ -468,6 +551,7 @@ static int vhost_vdpa_dev_start(struct vhost_dev *dev, bool started)
     if (started) {
         uint8_t status = 0;
         memory_listener_register(&v->listener, &address_space_memory);
+        vhost_vdpa_host_notifiers_init(dev);
         vhost_vdpa_set_vring_ready(dev);
         vhost_vdpa_add_status(dev, VIRTIO_CONFIG_S_DRIVER_OK);
         vhost_vdpa_call(dev, VHOST_VDPA_GET_STATUS, &status);
@@ -477,6 +561,7 @@ static int vhost_vdpa_dev_start(struct vhost_dev *dev, bool started)
         vhost_vdpa_reset_device(dev);
         vhost_vdpa_add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE |
                                    VIRTIO_CONFIG_S_DRIVER);
+        vhost_vdpa_host_notifiers_uninit(dev, dev->nvqs);
         memory_listener_unregister(&v->listener);
 
         return 0;

include/hw/virtio/vhost-vdpa.h

@@ -14,11 +14,17 @@
 
 #include "hw/virtio/virtio.h"
 
+typedef struct VhostVDPAHostNotifier {
+    MemoryRegion mr;
+    void *addr;
+} VhostVDPAHostNotifier;
+
 typedef struct vhost_vdpa {
     int device_fd;
     uint32_t msg_type;
     MemoryListener listener;
     struct vhost_dev *dev;
+    VhostVDPAHostNotifier notifier[VIRTIO_QUEUE_MAX];
 } VhostVDPA;
 
 #endif