net/virtio: fix memory init with vDPA backend

This patch fixes an overhead met with mlx5-vdpa Kernel
driver, where for every page in the mapped area, all the
memory tables gets updated. For example, with 2MB hugepages,
a single IOTLB_UPDATE for a 1GB region causes 512 memory
updates on mlx5-vdpa side.

Using batching mode, the mlx5 driver will only trigger a
single memory update for all the IOTLB updates that happen
between the batch begin and batch end commands.

Fixes: 6b901437056e ("net/virtio: introduce vhost-vDPA backend")
Cc: stable@dpdk.org
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Reviewed-by: Chenbo Xia <chenbo.xia@intel.com>

diff --git a/drivers/net/virtio/virtio_user/vhost.h b/drivers/net/virtio/virtio_user/vhost.h
index c1dcc50..be28617 100644 (file)
--- a/drivers/net/virtio/virtio_user/vhost.h
+++ b/drivers/net/virtio/virtio_user/vhost.h
@@ -90,6 +90,10 @@ enum vhost_user_request {
 #define VHOST_BACKEND_F_IOTLB_MSG_V2 1
 #endif
 
+#ifndef VHOST_BACKEND_F_IOTLB_BATCH
+#define VHOST_BACKEND_F_IOTLB_BATCH 2
+#endif
+
 extern const char * const vhost_msg_strings[VHOST_USER_MAX];
 
 struct vhost_memory_region {

diff --git a/drivers/net/virtio/virtio_user/vhost_vdpa.c b/drivers/net/virtio/virtio_user/vhost_vdpa.c
index 83c60ea..004802b 100644 (file)
--- a/drivers/net/virtio/virtio_user/vhost_vdpa.c
+++ b/drivers/net/virtio/virtio_user/vhost_vdpa.c
@@ -70,6 +70,8 @@ struct vhost_iotlb_msg {
 #define VHOST_IOTLB_UPDATE         2
 #define VHOST_IOTLB_INVALIDATE     3
 #define VHOST_IOTLB_ACCESS_FAIL    4
+#define VHOST_IOTLB_BATCH_BEGIN    5
+#define VHOST_IOTLB_BATCH_END      6
        uint8_t type;
 };
 
@@ -84,6 +86,56 @@ struct vhost_msg {
        };
 };
 
+static int
+vhost_vdpa_iotlb_batch_begin(struct virtio_user_dev *dev)
+{
+       struct vhost_msg msg = {};
+
+       if (!(dev->protocol_features & (1ULL << VHOST_BACKEND_F_IOTLB_BATCH)))
+               return 0;
+
+       if (!(dev->protocol_features & (1ULL << VHOST_BACKEND_F_IOTLB_MSG_V2))) {
+               PMD_DRV_LOG(ERR, "IOTLB_MSG_V2 not supported by the backend.");
+               return -1;
+       }
+
+       msg.type = VHOST_IOTLB_MSG_V2;
+       msg.iotlb.type = VHOST_IOTLB_BATCH_BEGIN;
+
+       if (write(dev->vhostfd, &msg, sizeof(msg)) != sizeof(msg)) {
+               PMD_DRV_LOG(ERR, "Failed to send IOTLB batch begin (%s)",
+                               strerror(errno));
+               return -1;
+       }
+
+       return 0;
+}
+
+static int
+vhost_vdpa_iotlb_batch_end(struct virtio_user_dev *dev)
+{
+       struct vhost_msg msg = {};
+
+       if (!(dev->protocol_features & (1ULL << VHOST_BACKEND_F_IOTLB_BATCH)))
+               return 0;
+
+       if (!(dev->protocol_features & (1ULL << VHOST_BACKEND_F_IOTLB_MSG_V2))) {
+               PMD_DRV_LOG(ERR, "IOTLB_MSG_V2 not supported by the backend.");
+               return -1;
+       }
+
+       msg.type = VHOST_IOTLB_MSG_V2;
+       msg.iotlb.type = VHOST_IOTLB_BATCH_END;
+
+       if (write(dev->vhostfd, &msg, sizeof(msg)) != sizeof(msg)) {
+               PMD_DRV_LOG(ERR, "Failed to send IOTLB batch end (%s)",
+                               strerror(errno));
+               return -1;
+       }
+
+       return 0;
+}
+
 static int
 vhost_vdpa_dma_map(struct virtio_user_dev *dev, void *addr,
                                  uint64_t iova, size_t len)
@@ -142,6 +194,39 @@ vhost_vdpa_dma_unmap(struct virtio_user_dev *dev, __rte_unused void *addr,
        return 0;
 }
 
+static int
+vhost_vdpa_dma_map_batch(struct virtio_user_dev *dev, void *addr,
+                                 uint64_t iova, size_t len)
+{
+       int ret;
+
+       if (vhost_vdpa_iotlb_batch_begin(dev) < 0)
+               return -1;
+
+       ret = vhost_vdpa_dma_map(dev, addr, iova, len);
+
+       if (vhost_vdpa_iotlb_batch_end(dev) < 0)
+               return -1;
+
+       return ret;
+}
+
+static int
+vhost_vdpa_dma_unmap_batch(struct virtio_user_dev *dev, void *addr,
+                                 uint64_t iova, size_t len)
+{
+       int ret;
+
+       if (vhost_vdpa_iotlb_batch_begin(dev) < 0)
+               return -1;
+
+       ret = vhost_vdpa_dma_unmap(dev, addr, iova, len);
+
+       if (vhost_vdpa_iotlb_batch_end(dev) < 0)
+               return -1;
+
+       return ret;
+}
 
 static int
 vhost_vdpa_map_contig(const struct rte_memseg_list *msl,
@@ -179,21 +264,32 @@ vhost_vdpa_map(const struct rte_memseg_list *msl, const struct rte_memseg *ms,
 static int
 vhost_vdpa_dma_map_all(struct virtio_user_dev *dev)
 {
+       int ret;
+
+       if (vhost_vdpa_iotlb_batch_begin(dev) < 0)
+               return -1;
+
        vhost_vdpa_dma_unmap(dev, NULL, 0, SIZE_MAX);
 
        if (rte_eal_iova_mode() == RTE_IOVA_VA) {
                /* with IOVA as VA mode, we can get away with mapping contiguous
                 * chunks rather than going page-by-page.
                 */
-               int ret = rte_memseg_contig_walk_thread_unsafe(
+               ret = rte_memseg_contig_walk_thread_unsafe(
                                vhost_vdpa_map_contig, dev);
                if (ret)
-                       return ret;
+                       goto batch_end;
                /* we have to continue the walk because we've skipped the
                 * external segments during the config walk.
                 */
        }
-       return rte_memseg_walk_thread_unsafe(vhost_vdpa_map, dev);
+       ret = rte_memseg_walk_thread_unsafe(vhost_vdpa_map, dev);
+
+batch_end:
+       if (vhost_vdpa_iotlb_batch_end(dev) < 0)
+               return -1;
+
+       return ret;
 }
 
 /* with below features, vhost vdpa does not need to do the checksum and TSO,
@@ -313,6 +409,6 @@ struct virtio_user_backend_ops virtio_ops_vdpa = {
        .setup = vhost_vdpa_setup,
        .send_request = vhost_vdpa_ioctl,
        .enable_qp = vhost_vdpa_enable_queue_pair,
-       .dma_map = vhost_vdpa_dma_map,
-       .dma_unmap = vhost_vdpa_dma_unmap,
+       .dma_map = vhost_vdpa_dma_map_batch,
+       .dma_unmap = vhost_vdpa_dma_unmap_batch,
 };

diff --git a/drivers/net/virtio/virtio_user/virtio_user_dev.c b/drivers/net/virtio/virtio_user/virtio_user_dev.c
index 39c5dfc..202431c 100644 (file)
--- a/drivers/net/virtio/virtio_user/virtio_user_dev.c
+++ b/drivers/net/virtio/virtio_user/virtio_user_dev.c
@@ -446,7 +446,8 @@ virtio_user_dev_setup(struct virtio_user_dev *dev)
         1ULL << VHOST_USER_PROTOCOL_F_STATUS)
 
 #define VHOST_VDPA_SUPPORTED_PROTOCOL_FEATURES         \
-       (1ULL << VHOST_BACKEND_F_IOTLB_MSG_V2)
+       (1ULL << VHOST_BACKEND_F_IOTLB_MSG_V2   |       \
+       1ULL << VHOST_BACKEND_F_IOTLB_BATCH)
 int
 virtio_user_dev_init(struct virtio_user_dev *dev, char *path, int queues,
                     int cq, int queue_size, const char *mac, char **ifname,