Re: [dpdk-dev] [PATCH v3 2/2] vhost: enable IOMMU for async vhost

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

Hi Xuan,

> -----Original Message-----
> From: Ding, Xuan <xuan.ding@intel.com>
> Sent: Saturday, September 25, 2021 6:04 PM
> To: dev@dpdk.org; Burakov, Anatoly <anatoly.burakov@intel.com>;
> maxime.coquelin@redhat.com; Xia, Chenbo <chenbo.xia@intel.com>
> Cc: Hu, Jiayu <jiayu.hu@intel.com>; Jiang, Cheng1 <cheng1.jiang@intel.com>;
> Richardson, Bruce <bruce.richardson@intel.com>; Pai G, Sunil
> <sunil.pai.g@intel.com>; Wang, Yinan <yinan.wang@intel.com>; Yang,
> YvonneX <yvonnex.yang@intel.com>; Ding, Xuan <xuan.ding@intel.com>
> Subject: [PATCH v3 2/2] vhost: enable IOMMU for async vhost
> 
> The use of IOMMU has many advantages, such as isolation and address
> translation. This patch extends the capbility of DMA engine to use IOMMU if
> the DMA engine is bound to vfio.
> 
> When set memory table, the guest memory will be mapped into the default
> container of DPDK.
> 
> Signed-off-by: Xuan Ding <xuan.ding@intel.com>
> ---
>  lib/vhost/vhost.h      |   4 ++
>  lib/vhost/vhost_user.c | 112
> ++++++++++++++++++++++++++++++++++++++++-
>  2 files changed, 114 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/vhost/vhost.h b/lib/vhost/vhost.h index
> 89a31e4ca8..bc5695e899 100644
> --- a/lib/vhost/vhost.h
> +++ b/lib/vhost/vhost.h
> @@ -370,6 +370,10 @@ struct virtio_net {
>  	int16_t			broadcast_rarp;
>  	uint32_t		nr_vring;
>  	int			async_copy;
> +
> +	/* Record the dma map status for each region. */
> +	bool			*async_map_status;
> +
>  	int			extbuf;
>  	int			linearbuf;
>  	struct vhost_virtqueue	*virtqueue[VHOST_MAX_QUEUE_PAIRS * 2];
> diff --git a/lib/vhost/vhost_user.c b/lib/vhost/vhost_user.c index
> 29a4c9af60..3990e9b057 100644
> --- a/lib/vhost/vhost_user.c
> +++ b/lib/vhost/vhost_user.c
> @@ -45,6 +45,8 @@
>  #include <rte_common.h>
>  #include <rte_malloc.h>
>  #include <rte_log.h>
> +#include <rte_vfio.h>
> +#include <rte_errno.h>
> 
>  #include "iotlb.h"
>  #include "vhost.h"
> @@ -141,6 +143,63 @@ get_blk_size(int fd)
>  	return ret == -1 ? (uint64_t)-1 : (uint64_t)stat.st_blksize;  }
> 
> +static int
> +async_dma_map(struct rte_vhost_mem_region *region, bool
> +*dma_map_success, bool do_map) {
> +	uint64_t host_iova;
> +	int ret = 0;
> +
> +	host_iova = rte_mem_virt2iova((void *)(uintptr_t)region-
> >host_user_addr);
> +	if (do_map) {
> +		/* Add mapped region into the default container of DPDK. */
> +		ret =
> rte_vfio_container_dma_map(RTE_VFIO_DEFAULT_CONTAINER_FD,
> +						 region->host_user_addr,
> +						 host_iova,
> +						 region->size);
> +		*dma_map_success = ret == 0;
> +
> +		if (ret) {
> +			/*
> +			 * DMA device may bind with kernel driver, in this
> case,
> +			 * we don't need to program IOMMU manually.
> However, if no
> +			 * device is bound with vfio/uio in DPDK, and vfio
> kernel
> +			 * module is loaded, the API will still be called and
> return
> +			 * with ENODEV/ENOSUP.
> +			 *
> +			 * DPDK VFIO only returns ENODEV/ENOSUP in very
> similar
> +			 * situations(VFIO either unsupported, or supported
> +			 * but no devices found). Either way, no mappings
> could be
> +			 * performed. We treat it as normal case in async
> path.
> +			 */
> +			if (rte_errno == ENODEV && rte_errno == ENOTSUP) {
> +				return 0;
> +			} else {
> +				VHOST_LOG_CONFIG(ERR, "DMA engine map
> failed\n");
> +				return ret;
> +			}
> +		}
> +
> +	} else {
> +		/* No need to do vfio unmap if the map failed. */
> +		if (!*dma_map_success)
> +			return 0;
> +
> +		/* Remove mapped region from the default container of
> DPDK. */
> +		ret =
> rte_vfio_container_dma_unmap(RTE_VFIO_DEFAULT_CONTAINER_FD,
> +						   region->host_user_addr,
> +						   host_iova,
> +						   region->size);
> +		if (ret) {
> +			VHOST_LOG_CONFIG(ERR, "DMA engine unmap
> failed\n");
> +			return ret;
> +		}
> +		/* Clear the flag once the unmap succeeds. */
> +		*dma_map_success = 0;
> +	}
> +
> +	return ret;
> +}
> +
>  static void
>  free_mem_region(struct virtio_net *dev)  { @@ -153,6 +212,9 @@
> free_mem_region(struct virtio_net *dev)
>  	for (i = 0; i < dev->mem->nregions; i++) {
>  		reg = &dev->mem->regions[i];
>  		if (reg->host_user_addr) {
> +			if (dev->async_copy && rte_vfio_is_enabled("vfio"))
> +				async_dma_map(reg, &dev-
> >async_map_status[i], false);
> +
>  			munmap(reg->mmap_addr, reg->mmap_size);
>  			close(reg->fd);
>  		}
> @@ -203,6 +265,11 @@ vhost_backend_cleanup(struct virtio_net *dev)
>  	}
> 
>  	dev->postcopy_listening = 0;
> +
> +	if (dev->async_map_status) {
> +		rte_free(dev->async_map_status);
> +		dev->async_map_status = NULL;
> +	}
>  }
> 
>  static void
> @@ -621,6 +688,17 @@ numa_realloc(struct virtio_net *dev, int index)
>  	}
>  	dev->mem = mem;
> 
> +	if (dev->async_copy && rte_vfio_is_enabled("vfio")) {
> +		dev->async_map_status = rte_zmalloc_socket("async-dma-
> map-status",
> +					sizeof(bool) * dev->mem->nregions,
> 0, node);
> +		if (!dev->async_map_status) {
> +			VHOST_LOG_CONFIG(ERR,
> +				"(%d) failed to realloc dma mapping status on
> node\n",
> +				dev->vid);
> +			return dev;
> +		}
> +	}
> +
>  	gp = rte_realloc_socket(dev->guest_pages, dev->max_guest_pages *
> sizeof(*gp),
>  			RTE_CACHE_LINE_SIZE, node);
>  	if (!gp) {
> @@ -1151,12 +1229,14 @@ vhost_user_postcopy_register(struct virtio_net
> *dev, int main_fd,  static int  vhost_user_mmap_region(struct virtio_net *dev,
>  		struct rte_vhost_mem_region *region,
> +		uint32_t region_index,
>  		uint64_t mmap_offset)
>  {
>  	void *mmap_addr;
>  	uint64_t mmap_size;
>  	uint64_t alignment;
>  	int populate;
> +	int ret;
> 
>  	/* Check for memory_size + mmap_offset overflow */
>  	if (mmap_offset >= -region->size) {
> @@ -1210,13 +1290,25 @@ vhost_user_mmap_region(struct virtio_net *dev,
>  	region->mmap_size = mmap_size;
>  	region->host_user_addr = (uint64_t)(uintptr_t)mmap_addr +
> mmap_offset;
> 
> -	if (dev->async_copy)
> +	if (dev->async_copy) {
>  		if (add_guest_pages(dev, region, alignment) < 0) {
>  			VHOST_LOG_CONFIG(ERR,
>  					"adding guest pages to region
> failed.\n");
>  			return -1;
>  		}
> 
> +		if (rte_vfio_is_enabled("vfio")) {
> +			ret = async_dma_map(region, &dev-
> >async_map_status[region_index], true);
> +			if (ret) {
> +				VHOST_LOG_CONFIG(ERR, "Configure
> IOMMU for DMA "
> +							"engine failed\n");
> +				rte_free(dev->async_map_status);
> +				dev->async_map_status = NULL;

The freed dev->async_map_status is accessed in free_mem_region() later.
You need to free it after calling free_mem_region().

> +				return -1;
> +			}
> +		}
> +	}
> +
>  	VHOST_LOG_CONFIG(INFO,
>  			"guest memory region size: 0x%" PRIx64 "\n"
>  			"\t guest physical addr: 0x%" PRIx64 "\n"
> @@ -1291,6 +1383,11 @@ vhost_user_set_mem_table(struct virtio_net
> **pdev, struct VhostUserMsg *msg,
>  		dev->mem = NULL;
>  	}
> 
> +	if (dev->async_map_status) {
> +		rte_free(dev->async_map_status);
> +		dev->async_map_status = NULL;
> +	}

To handle the gust memory hot-plug case, you need to un-map
iommu tables before program iommu for new memory. But you
seem only free the old dev->async_map_status.

Thanks,
Jiayu

> +
>  	/* Flush IOTLB cache as previous HVAs are now invalid */
>  	if (dev->features & (1ULL << VIRTIO_F_IOMMU_PLATFORM))
>  		for (i = 0; i < dev->nr_vring; i++)
> @@ -1329,6 +1426,17 @@ vhost_user_set_mem_table(struct virtio_net
> **pdev, struct VhostUserMsg *msg,
>  		goto free_guest_pages;
>  	}
> 
> +	if (dev->async_copy) {
> +		dev->async_map_status = rte_zmalloc_socket("async-dma-
> map-status",
> +					sizeof(bool) * memory->nregions, 0,
> numa_node);
> +		if (!dev->async_map_status) {
> +			VHOST_LOG_CONFIG(ERR,
> +				"(%d) failed to allocate memory for dma
> mapping status\n",
> +				dev->vid);
> +			goto free_guest_pages;
> +		}
> +	}
> +
>  	for (i = 0; i < memory->nregions; i++) {
>  		reg = &dev->mem->regions[i];
> 
> @@ -1345,7 +1453,7 @@ vhost_user_set_mem_table(struct virtio_net
> **pdev, struct VhostUserMsg *msg,
> 
>  		mmap_offset = memory->regions[i].mmap_offset;
> 
> -		if (vhost_user_mmap_region(dev, reg, mmap_offset) < 0) {
> +		if (vhost_user_mmap_region(dev, reg, i, mmap_offset) < 0) {
>  			VHOST_LOG_CONFIG(ERR, "Failed to mmap
> region %u\n", i);
>  			goto free_mem_table;
>  		}
> --
> 2.17.1