[PATCH 3/3] vhost-vdpa: batch updating IOTLB mappings

[Jason Wang <jasowang@redhat.com>]

To speed up the memory mapping updating between vhost-vDPA and vDPA
device driver, this patch passes the IOTLB batching flags via IOTLB
API. Two new flags was introduced, VHOST_IOTLB_BATCH_BEGIN is a hint
that a bathced IOTLB updating may be initiated from the
userspace. VHOST_IOTLB_BATCH_END is a hint that userspace has finished
the updating:

VHOST_IOTLB_BATCH_BEGIN
VHOST_IOTLB_UPDATE/VHOST_IOTLB_INVALIDATE
...
VHOST_IOTLB_BATCH_END

Vhost-vDPA can then know that all mappings has been set and can do
optimization like passing all the mappings to the vDPA device driver.

Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 hw/virtio/vhost-vdpa.c         | 66 ++++++++++++++++++++++++++++++++++
 include/hw/virtio/vhost-vdpa.h |  1 +
 2 files changed, 67 insertions(+)

diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index 4580f3efd8..ba1ae3ea44 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -78,6 +78,46 @@ static int vhost_vdpa_dma_unmap(struct vhost_vdpa *v, hwaddr iova,
     return ret;
 }
 
+static void vhost_vdpa_listener_begin(MemoryListener *listener)
+{
+    struct vhost_vdpa *v = container_of(listener, struct vhost_vdpa, listener);
+    struct vhost_dev *dev = v->dev;
+    struct vhost_msg_v2 msg;
+    int fd = v->device_fd;
+
+    if (!(dev->backend_cap & (0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH))) {
+        return;
+    }
+
+    msg.type = v->msg_type;
+    msg.iotlb.type = VHOST_IOTLB_BATCH_BEGIN;
+
+    if (write(fd, &msg, sizeof(msg)) != sizeof(msg)) {
+        error_report("failed to write, fd=%d, errno=%d (%s)",
+                     fd, errno, strerror(errno));
+    }
+}
+
+static void vhost_vdpa_listener_commit(MemoryListener *listener)
+{
+    struct vhost_vdpa *v = container_of(listener, struct vhost_vdpa, listener);
+    struct vhost_dev *dev = v->dev;
+    struct vhost_msg_v2 msg;
+    int fd = v->device_fd;
+
+    if (!(dev->backend_cap & (0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH))) {
+        return;
+    }
+
+    msg.type = v->msg_type;
+    msg.iotlb.type = VHOST_IOTLB_BATCH_END;
+
+    if (write(fd, &msg, sizeof(msg)) != sizeof(msg)) {
+        error_report("failed to write, fd=%d, errno=%d (%s)",
+                     fd, errno, strerror(errno));
+    }
+}
+
 static void vhost_vdpa_listener_region_add(MemoryListener *listener,
                                            MemoryRegionSection *section)
 {
@@ -191,6 +231,8 @@ static void vhost_vdpa_listener_region_del(MemoryListener *listener,
  * depends on the addnop().
  */
 static const MemoryListener vhost_vdpa_memory_listener = {
+    .begin = vhost_vdpa_listener_begin,
+    .commit = vhost_vdpa_listener_commit,
     .region_add = vhost_vdpa_listener_region_add,
     .region_del = vhost_vdpa_listener_region_del,
 };
@@ -226,6 +268,7 @@ static int vhost_vdpa_init(struct vhost_dev *dev, void *opaque)
     assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_VDPA);
 
     v = opaque;
+    v->dev = dev;
     dev->opaque =  opaque ;
     vhost_vdpa_call(dev, VHOST_GET_FEATURES, &features);
     dev->backend_features = features;
@@ -280,6 +323,28 @@ static int vhost_vdpa_set_features(struct vhost_dev *dev,
     return !(status & VIRTIO_CONFIG_S_FEATURES_OK);
 }
 
+static int vhost_vdpa_set_backend_cap(struct vhost_dev *dev)
+{
+    uint64_t features;
+    uint64_t f = 0x1ULL << VHOST_BACKEND_F_IOTLB_MSG_V2 |
+        0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH;
+    int r;
+
+    if (vhost_vdpa_call(dev, VHOST_GET_BACKEND_FEATURES, &features)) {
+        return 0;
+    }
+
+    features &= f;
+    r = vhost_vdpa_call(dev, VHOST_SET_BACKEND_FEATURES, &features);
+    if (r) {
+        return 0;
+    }
+
+    dev->backend_cap = features;
+
+    return 0;
+}
+
 int vhost_vdpa_get_device_id(struct vhost_dev *dev,
                                    uint32_t *device_id)
 {
@@ -452,6 +517,7 @@ const VhostOps vdpa_ops = {
         .vhost_set_vring_kick = vhost_vdpa_set_vring_kick,
         .vhost_set_vring_call = vhost_vdpa_set_vring_call,
         .vhost_get_features = vhost_vdpa_get_features,
+        .vhost_set_backend_cap = vhost_vdpa_set_backend_cap,
         .vhost_set_owner = vhost_vdpa_set_owner,
         .vhost_set_vring_endian = NULL,
         .vhost_backend_memslots_limit = vhost_vdpa_memslots_limit,
diff --git a/include/hw/virtio/vhost-vdpa.h b/include/hw/virtio/vhost-vdpa.h
index 6455663388..9b81a409da 100644
--- a/include/hw/virtio/vhost-vdpa.h
+++ b/include/hw/virtio/vhost-vdpa.h
@@ -18,6 +18,7 @@ typedef struct vhost_vdpa {
     int device_fd;
     uint32_t msg_type;
     MemoryListener listener;
+    struct vhost_dev *dev;
 } VhostVDPA;
 
 extern AddressSpace address_space_memory;
-- 
2.20.1