Re: [RFC v3 05/11] vdpa: shared virtual addressing support

[Jason Wang <jasowang@redhat.com>]

On 2021/1/19 下午12:59, Xie Yongji wrote:
> This patches introduces SVA (Shared Virtual Addressing)
> support for vDPA device. During vDPA device allocation,
> vDPA device driver needs to indicate whether SVA is
> supported by the device. Then vhost-vdpa bus driver
> will not pin user page and transfer userspace virtual
> address instead of physical address during DMA mapping.
>
> Suggested-by: Jason Wang <jasowang@redhat.com>
> Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
> ---
>   drivers/vdpa/ifcvf/ifcvf_main.c   |  2 +-
>   drivers/vdpa/mlx5/net/mlx5_vnet.c |  2 +-
>   drivers/vdpa/vdpa.c               |  5 ++++-
>   drivers/vdpa/vdpa_sim/vdpa_sim.c  |  3 ++-
>   drivers/vhost/vdpa.c              | 35 +++++++++++++++++++++++------------
>   include/linux/vdpa.h              | 10 +++++++---
>   6 files changed, 38 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/vdpa/ifcvf/ifcvf_main.c b/drivers/vdpa/ifcvf/ifcvf_main.c
> index 23474af7da40..95c4601f82f5 100644
> --- a/drivers/vdpa/ifcvf/ifcvf_main.c
> +++ b/drivers/vdpa/ifcvf/ifcvf_main.c
> @@ -439,7 +439,7 @@ static int ifcvf_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>   
>   	adapter = vdpa_alloc_device(struct ifcvf_adapter, vdpa,
>   				    dev, &ifc_vdpa_ops,
> -				    IFCVF_MAX_QUEUE_PAIRS * 2, NULL);
> +				    IFCVF_MAX_QUEUE_PAIRS * 2, NULL, false);
>   	if (adapter == NULL) {
>   		IFCVF_ERR(pdev, "Failed to allocate vDPA structure");
>   		return -ENOMEM;
> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> index 77595c81488d..05988d6907f2 100644
> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> @@ -1959,7 +1959,7 @@ static int mlx5v_probe(struct auxiliary_device *adev,
>   	max_vqs = min_t(u32, max_vqs, MLX5_MAX_SUPPORTED_VQS);
>   
>   	ndev = vdpa_alloc_device(struct mlx5_vdpa_net, mvdev.vdev, mdev->device, &mlx5_vdpa_ops,
> -				 2 * mlx5_vdpa_max_qps(max_vqs), NULL);
> +				 2 * mlx5_vdpa_max_qps(max_vqs), NULL, false);
>   	if (IS_ERR(ndev))
>   		return PTR_ERR(ndev);
>   
> diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c
> index 32bd48baffab..50cab930b2e5 100644
> --- a/drivers/vdpa/vdpa.c
> +++ b/drivers/vdpa/vdpa.c
> @@ -72,6 +72,7 @@ static void vdpa_release_dev(struct device *d)
>    * @nvqs: number of virtqueues supported by this device
>    * @size: size of the parent structure that contains private data
>    * @name: name of the vdpa device; optional.
> + * @sva: indicate whether SVA (Shared Virtual Addressing) is supported
>    *
>    * Driver should use vdpa_alloc_device() wrapper macro instead of
>    * using this directly.
> @@ -81,7 +82,8 @@ static void vdpa_release_dev(struct device *d)
>    */
>   struct vdpa_device *__vdpa_alloc_device(struct device *parent,
>   					const struct vdpa_config_ops *config,
> -					int nvqs, size_t size, const char *name)
> +					int nvqs, size_t size, const char *name,
> +					bool sva)
>   {
>   	struct vdpa_device *vdev;
>   	int err = -EINVAL;
> @@ -108,6 +110,7 @@ struct vdpa_device *__vdpa_alloc_device(struct device *parent,
>   	vdev->config = config;
>   	vdev->features_valid = false;
>   	vdev->nvqs = nvqs;
> +	vdev->sva = sva;
>   
>   	if (name)
>   		err = dev_set_name(&vdev->dev, "%s", name);
> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> index 85776e4e6749..03c796873a6b 100644
> --- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
> +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> @@ -367,7 +367,8 @@ static struct vdpasim *vdpasim_create(const char *name)
>   	else
>   		ops = &vdpasim_net_config_ops;
>   
> -	vdpasim = vdpa_alloc_device(struct vdpasim, vdpa, NULL, ops, VDPASIM_VQ_NUM, name);
> +	vdpasim = vdpa_alloc_device(struct vdpasim, vdpa, NULL, ops,
> +				VDPASIM_VQ_NUM, name, false);
>   	if (!vdpasim)
>   		goto err_alloc;
>   
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index 4a241d380c40..36b6950ba37f 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -486,21 +486,25 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
>   static void vhost_vdpa_iotlb_unmap(struct vhost_vdpa *v, u64 start, u64 last)
>   {
>   	struct vhost_dev *dev = &v->vdev;
> +	struct vdpa_device *vdpa = v->vdpa;
>   	struct vhost_iotlb *iotlb = dev->iotlb;
>   	struct vhost_iotlb_map *map;
>   	struct page *page;
>   	unsigned long pfn, pinned;
>   
>   	while ((map = vhost_iotlb_itree_first(iotlb, start, last)) != NULL) {
> -		pinned = map->size >> PAGE_SHIFT;
> -		for (pfn = map->addr >> PAGE_SHIFT;
> -		     pinned > 0; pfn++, pinned--) {
> -			page = pfn_to_page(pfn);
> -			if (map->perm & VHOST_ACCESS_WO)
> -				set_page_dirty_lock(page);
> -			unpin_user_page(page);
> +		if (!vdpa->sva) {
> +			pinned = map->size >> PAGE_SHIFT;
> +			for (pfn = map->addr >> PAGE_SHIFT;
> +			     pinned > 0; pfn++, pinned--) {
> +				page = pfn_to_page(pfn);
> +				if (map->perm & VHOST_ACCESS_WO)
> +					set_page_dirty_lock(page);
> +				unpin_user_page(page);
> +			}
> +			atomic64_sub(map->size >> PAGE_SHIFT,
> +					&dev->mm->pinned_vm);
>   		}
> -		atomic64_sub(map->size >> PAGE_SHIFT, &dev->mm->pinned_vm);
>   		vhost_iotlb_map_free(iotlb, map);
>   	}
>   }
> @@ -558,13 +562,15 @@ static int vhost_vdpa_map(struct vhost_vdpa *v,
>   		r = iommu_map(v->domain, iova, pa, size,
>   			      perm_to_iommu_flags(perm));
>   	}
> -
> -	if (r)
> +	if (r) {
>   		vhost_iotlb_del_range(dev->iotlb, iova, iova + size - 1);
> -	else
> +		return r;
> +	}
> +
> +	if (!vdpa->sva)
>   		atomic64_add(size >> PAGE_SHIFT, &dev->mm->pinned_vm);
>   
> -	return r;
> +	return 0;
>   }
>   
>   static void vhost_vdpa_unmap(struct vhost_vdpa *v, u64 iova, u64 size)
> @@ -589,6 +595,7 @@ static int vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v,
>   					   struct vhost_iotlb_msg *msg)
>   {
>   	struct vhost_dev *dev = &v->vdev;
> +	struct vdpa_device *vdpa = v->vdpa;
>   	struct vhost_iotlb *iotlb = dev->iotlb;
>   	struct page **page_list;
>   	unsigned long list_size = PAGE_SIZE / sizeof(struct page *);
> @@ -607,6 +614,10 @@ static int vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v,
>   				    msg->iova + msg->size - 1))
>   		return -EEXIST;
>   
> +	if (vdpa->sva)
> +		return vhost_vdpa_map(v, msg->iova, msg->size,
> +				      msg->uaddr, msg->perm);
> +
>   	/* Limit the use of memory for bookkeeping */
>   	page_list = (struct page **) __get_free_page(GFP_KERNEL);
>   	if (!page_list)
> diff --git a/include/linux/vdpa.h b/include/linux/vdpa.h
> index cb5a3d847af3..f86869651614 100644
> --- a/include/linux/vdpa.h
> +++ b/include/linux/vdpa.h
> @@ -44,6 +44,7 @@ struct vdpa_parent_dev;
>    * @config: the configuration ops for this device.
>    * @index: device index
>    * @features_valid: were features initialized? for legacy guests
> + * @sva: indicate whether SVA (Shared Virtual Addressing) is supported


Rethink about this. I think we probably need a better name other than 
"sva" since kernel already use that for shared virtual address space. 
But actually we don't the whole virtual address space.

And I guess this can not work for the device that use platform IOMMU, so 
we should check and fail if sva && !(dma_map || set_map).

Thanks


>    * @nvqs: maximum number of supported virtqueues
>    * @pdev: parent device pointer; caller must setup when registering device as part
>    *	  of dev_add() parentdev ops callback before invoking _vdpa_register_device().
> @@ -54,6 +55,7 @@ struct vdpa_device {
>   	const struct vdpa_config_ops *config;
>   	unsigned int index;
>   	bool features_valid;
> +	bool sva;
>   	int nvqs;
>   	struct vdpa_parent_dev *pdev;
>   };
> @@ -250,14 +252,16 @@ struct vdpa_config_ops {
>   
>   struct vdpa_device *__vdpa_alloc_device(struct device *parent,
>   					const struct vdpa_config_ops *config,
> -					int nvqs, size_t size, const char *name);
> +					int nvqs, size_t size,
> +					const char *name, bool sva);
>   
> -#define vdpa_alloc_device(dev_struct, member, parent, config, nvqs, name)   \
> +#define vdpa_alloc_device(dev_struct, member, parent, config, \
> +			  nvqs, name, sva) \
>   			  container_of(__vdpa_alloc_device( \
>   				       parent, config, nvqs, \
>   				       sizeof(dev_struct) + \
>   				       BUILD_BUG_ON_ZERO(offsetof( \
> -				       dev_struct, member)), name), \
> +				       dev_struct, member)), name, sva), \
>   				       dev_struct, member)
>   
>   int vdpa_register_device(struct vdpa_device *vdev);

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