[dpdk-dev] [PATCH 1/4] vhost: populate guest memory for DMA-accelerated vhost-user

[Jiayu Hu <jiayu.hu@intel.com>]

DMA engines, like I/OAT, are efficient in moving large data
within memory. Offloading large copies in vhost side to DMA
engines can save precious CPU cycles and improve vhost
performance.

However, using the DMA engine requires to populate guest's
memory. This patch is to enable DMA-accelerated vhost-user
to populate guest's memory.

Signed-off-by: Jiayu Hu <jiayu.hu@intel.com>
---
 lib/librte_vhost/rte_vhost.h  |  1 +
 lib/librte_vhost/socket.c     | 20 ++++++++++++++++++++
 lib/librte_vhost/vhost.h      |  2 ++
 lib/librte_vhost/vhost_user.c |  3 ++-
 4 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/lib/librte_vhost/rte_vhost.h b/lib/librte_vhost/rte_vhost.h
index c7b619a..8871249 100644
--- a/lib/librte_vhost/rte_vhost.h
+++ b/lib/librte_vhost/rte_vhost.h
@@ -35,6 +35,7 @@ extern "C" {
 #define RTE_VHOST_USER_EXTBUF_SUPPORT	(1ULL << 5)
 /* support only linear buffers (no chained mbufs) */
 #define RTE_VHOST_USER_LINEARBUF_SUPPORT	(1ULL << 6)
+#define RTE_VHOST_USER_DMA_COPY		(1ULL << 7)
 
 /** Protocol features. */
 #ifndef VHOST_USER_PROTOCOL_F_MQ
diff --git a/lib/librte_vhost/socket.c b/lib/librte_vhost/socket.c
index 7c80121..b811dc9 100644
--- a/lib/librte_vhost/socket.c
+++ b/lib/librte_vhost/socket.c
@@ -62,6 +62,8 @@ struct vhost_user_socket {
 	 */
 	int vdpa_dev_id;
 
+	bool dma_enabled;
+
 	struct vhost_device_ops const *notify_ops;
 };
 
@@ -241,6 +243,13 @@ vhost_user_add_connection(int fd, struct vhost_user_socket *vsocket)
 	if (vsocket->linearbuf)
 		vhost_enable_linearbuf(vid);
 
+	if (vsocket->dma_enabled) {
+		struct virtio_net *dev;
+
+		dev = get_device(vid);
+		dev->dma_enabled = true;
+	}
+
 	VHOST_LOG_CONFIG(INFO, "new device, handle is %d\n", vid);
 
 	if (vsocket->notify_ops->new_connection) {
@@ -891,6 +900,17 @@ rte_vhost_driver_register(const char *path, uint64_t flags)
 		goto out_mutex;
 	}
 
+	vsocket->dma_enabled = flags & RTE_VHOST_USER_DMA_COPY;
+
+	if (vsocket->dma_enabled &&
+	    (flags & (RTE_VHOST_USER_IOMMU_SUPPORT |
+		      RTE_VHOST_USER_POSTCOPY_SUPPORT))) {
+		VHOST_LOG_CONFIG(ERR, "error: enabling DMA copy and IOMMU "
+				 "or post-copy feature simultaneously is not "
+				 "supported\n");
+		goto out_mutex;
+	}
+
 	/*
 	 * Set the supported features correctly for the builtin vhost-user
 	 * net driver.
diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
index 2087d14..c245771 100644
--- a/lib/librte_vhost/vhost.h
+++ b/lib/librte_vhost/vhost.h
@@ -383,6 +383,8 @@ struct virtio_net {
 	 */
 	int			vdpa_dev_id;
 
+	bool			dma_enabled;
+
 	/* context data for the external message handlers */
 	void			*extern_data;
 	/* pre and post vhost user message handlers for the device */
diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
index bd1be01..9c8356a 100644
--- a/lib/librte_vhost/vhost_user.c
+++ b/lib/librte_vhost/vhost_user.c
@@ -1138,7 +1138,8 @@ vhost_user_set_mem_table(struct virtio_net **pdev, struct VhostUserMsg *msg,
 			goto err_mmap;
 		}
 
-		populate = (dev->dequeue_zero_copy) ? MAP_POPULATE : 0;
+		populate = (dev->dequeue_zero_copy || dev->dma_enabled) ?
+			MAP_POPULATE : 0;
 		mmap_addr = mmap(NULL, mmap_size, PROT_READ | PROT_WRITE,
 				 MAP_SHARED | populate, fd, 0);
 
-- 
2.7.4