[dpdk-stable] [PATCH 21.02 v2 2/2] net/virtio: fix memory init with vDPA backend

[Xia, Chenbo]

> -----Original Message-----
> From: Maxime Coquelin <maxime.coquelin at redhat.com>
> Sent: Wednesday, November 25, 2020 11:21 PM
> To: dev at dpdk.org; Xia, Chenbo <chenbo.xia at intel.com>; amorenoz at redhat.com;
> jasowang at redhat.com; david.marchand at redhat.com
> Cc: Maxime Coquelin <maxime.coquelin at redhat.com>; stable at dpdk.org
> Subject: [PATCH 21.02 v2 2/2] 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 at dpdk.org
> 
> Signed-off-by: Maxime Coquelin <maxime.coquelin at redhat.com>
> ---
>  drivers/net/virtio/virtio_user/vhost.h        |   4 +
>  drivers/net/virtio/virtio_user/vhost_vdpa.c   | 106 +++++++++++++++++-
>  .../net/virtio/virtio_user/virtio_user_dev.c  |   3 +-
>  3 files changed, 107 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/net/virtio/virtio_user/vhost.h
> b/drivers/net/virtio/virtio_user/vhost.h
> index c1dcc50b58..be286173b0 100644
> --- 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 b6c81d6f17..269bab2f8e 100644
> --- 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)
> @@ -136,6 +188,39 @@ 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,
> @@ -173,21 +258,32 @@ 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,
> @@ -307,6 +403,6 @@ 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 96bc6b232d..095deeea82 100644
> --- a/drivers/net/virtio/virtio_user/virtio_user_dev.c
> +++ b/drivers/net/virtio/virtio_user/virtio_user_dev.c
> @@ -445,7 +445,8 @@ 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,
> --
> 2.26.2

Reviewed-by: Chenbo Xia <chenbo.xia at intel.com>