On Fri, Jul 18, 2025 at 05:16:16PM +0800, Jason Wang wrote:
> Lacking the support of device specific mapping supported in virtio,
> VDUSE must trick the DMA API in order to make virtio-vdpa transport
> work. This is done by advertising vDPA device as dma device with a
> VDUSE specific dma_ops even if it doesn't do DMA at all.
>
> This will be fixed by this patch. Thanks to the new mapping operations
> support by virtio and vDPA. VDUSE can simply switch to advertise its
> specific mappings operations to virtio via virtio-vdpa then DMA API is
> not needed for VDUSE any more.
>
> Reviewed-by: Christoph Hellwig <h...@lst.de>
> Signed-off-by: Jason Wang <jasow...@redhat.com>
So with all this, how do we know we did not forget any
users of dma api?
> ---
> drivers/vdpa/Kconfig | 8 +------
> drivers/vdpa/vdpa_user/iova_domain.c | 2 +-
> drivers/vdpa/vdpa_user/iova_domain.h | 2 +-
> drivers/vdpa/vdpa_user/vduse_dev.c | 31 ++++++++++++++++------------
> 4 files changed, 21 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/vdpa/Kconfig b/drivers/vdpa/Kconfig
> index 559fb9d3271f..857cf288c876 100644
> --- a/drivers/vdpa/Kconfig
> +++ b/drivers/vdpa/Kconfig
> @@ -34,13 +34,7 @@ config VDPA_SIM_BLOCK
>
> config VDPA_USER
> tristate "VDUSE (vDPA Device in Userspace) support"
> - depends on EVENTFD && MMU && HAS_DMA
> - #
> - # This driver incorrectly tries to override the dma_ops. It should
> - # never have done that, but for now keep it working on architectures
> - # that use dma ops
> - #
> - depends on ARCH_HAS_DMA_OPS
> + depends on EVENTFD && MMU
> select VHOST_IOTLB
> select IOMMU_IOVA
> help
> diff --git a/drivers/vdpa/vdpa_user/iova_domain.c
> b/drivers/vdpa/vdpa_user/iova_domain.c
> index 019f3305c0ac..8ea311692545 100644
> --- a/drivers/vdpa/vdpa_user/iova_domain.c
> +++ b/drivers/vdpa/vdpa_user/iova_domain.c
> @@ -447,7 +447,7 @@ void vduse_domain_unmap_page(struct vduse_iova_domain
> *domain,
>
> void *vduse_domain_alloc_coherent(struct vduse_iova_domain *domain,
> size_t size, dma_addr_t *dma_addr,
> - gfp_t flag, unsigned long attrs)
> + gfp_t flag)
> {
> struct iova_domain *iovad = &domain->consistent_iovad;
> unsigned long limit = domain->iova_limit;
> diff --git a/drivers/vdpa/vdpa_user/iova_domain.h
> b/drivers/vdpa/vdpa_user/iova_domain.h
> index 846572b95c23..a2316571671f 100644
> --- a/drivers/vdpa/vdpa_user/iova_domain.h
> +++ b/drivers/vdpa/vdpa_user/iova_domain.h
> @@ -64,7 +64,7 @@ void vduse_domain_unmap_page(struct vduse_iova_domain
> *domain,
>
> void *vduse_domain_alloc_coherent(struct vduse_iova_domain *domain,
> size_t size, dma_addr_t *dma_addr,
> - gfp_t flag, unsigned long attrs);
> + gfp_t flag);
>
> void vduse_domain_free_coherent(struct vduse_iova_domain *domain, size_t
> size,
> void *vaddr, dma_addr_t dma_addr,
> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c
> b/drivers/vdpa/vdpa_user/vduse_dev.c
> index 934c50d15b28..d858c4389cc1 100644
> --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> @@ -814,51 +814,55 @@ static const struct vdpa_config_ops
> vduse_vdpa_config_ops = {
> .free = vduse_vdpa_free,
> };
>
> -static void vduse_dev_sync_single_for_device(struct device *dev,
> +static void vduse_dev_sync_single_for_device(void *token,
> dma_addr_t dma_addr, size_t size,
> enum dma_data_direction dir)
> {
> + struct device *dev = token;
> struct vduse_dev *vdev = dev_to_vduse(dev);
> struct vduse_iova_domain *domain = vdev->domain;
>
> vduse_domain_sync_single_for_device(domain, dma_addr, size, dir);
> }
>
> -static void vduse_dev_sync_single_for_cpu(struct device *dev,
> +static void vduse_dev_sync_single_for_cpu(void *token,
> dma_addr_t dma_addr, size_t size,
> enum dma_data_direction dir)
> {
> + struct device *dev = token;
> struct vduse_dev *vdev = dev_to_vduse(dev);
> struct vduse_iova_domain *domain = vdev->domain;
>
> vduse_domain_sync_single_for_cpu(domain, dma_addr, size, dir);
> }
>
> -static dma_addr_t vduse_dev_map_page(struct device *dev, struct page *page,
> +static dma_addr_t vduse_dev_map_page(void *token, struct page *page,
> unsigned long offset, size_t size,
> enum dma_data_direction dir,
> unsigned long attrs)
> {
> + struct device *dev = token;
> struct vduse_dev *vdev = dev_to_vduse(dev);
> struct vduse_iova_domain *domain = vdev->domain;
>
> return vduse_domain_map_page(domain, page, offset, size, dir, attrs);
> }
>
> -static void vduse_dev_unmap_page(struct device *dev, dma_addr_t dma_addr,
> +static void vduse_dev_unmap_page(void *token, dma_addr_t dma_addr,
> size_t size, enum dma_data_direction dir,
> unsigned long attrs)
> {
> + struct device *dev = token;
> struct vduse_dev *vdev = dev_to_vduse(dev);
> struct vduse_iova_domain *domain = vdev->domain;
>
> return vduse_domain_unmap_page(domain, dma_addr, size, dir, attrs);
> }
>
> -static void *vduse_dev_alloc_coherent(struct device *dev, size_t size,
> - dma_addr_t *dma_addr, gfp_t flag,
> - unsigned long attrs)
> +static void *vduse_dev_alloc_coherent(void *token, size_t size,
> + dma_addr_t *dma_addr, gfp_t flag)
> {
> + struct device *dev = token;
> struct vduse_dev *vdev = dev_to_vduse(dev);
> struct vduse_iova_domain *domain = vdev->domain;
> unsigned long iova;
> @@ -866,7 +870,7 @@ static void *vduse_dev_alloc_coherent(struct device *dev,
> size_t size,
>
> *dma_addr = DMA_MAPPING_ERROR;
> addr = vduse_domain_alloc_coherent(domain, size,
> - (dma_addr_t *)&iova, flag, attrs);
> + (dma_addr_t *)&iova, flag);
> if (!addr)
> return NULL;
>
> @@ -875,25 +879,27 @@ static void *vduse_dev_alloc_coherent(struct device
> *dev, size_t size,
> return addr;
> }
>
> -static void vduse_dev_free_coherent(struct device *dev, size_t size,
> +static void vduse_dev_free_coherent(void *token, size_t size,
> void *vaddr, dma_addr_t dma_addr,
> unsigned long attrs)
> {
> + struct device *dev = token;
> struct vduse_dev *vdev = dev_to_vduse(dev);
> struct vduse_iova_domain *domain = vdev->domain;
>
> vduse_domain_free_coherent(domain, size, vaddr, dma_addr, attrs);
> }
>
> -static size_t vduse_dev_max_mapping_size(struct device *dev)
> +static size_t vduse_dev_max_mapping_size(void *token)
> {
> + struct device *dev = token;
> struct vduse_dev *vdev = dev_to_vduse(dev);
> struct vduse_iova_domain *domain = vdev->domain;
>
> return domain->bounce_size;
> }
>
> -static const struct dma_map_ops vduse_dev_dma_ops = {
> +static const struct virtio_map_ops vduse_map_ops = {
> .sync_single_for_device = vduse_dev_sync_single_for_device,
> .sync_single_for_cpu = vduse_dev_sync_single_for_cpu,
> .map_page = vduse_dev_map_page,
> @@ -2009,7 +2015,7 @@ static int vduse_dev_init_vdpa(struct vduse_dev *dev,
> const char *name)
> return -EEXIST;
>
> vdev = vdpa_alloc_device(struct vduse_vdpa, vdpa, dev->dev,
> - &vduse_vdpa_config_ops, NULL,
> + &vduse_vdpa_config_ops, &vduse_map_ops,
> 1, 1, name, true);
> if (IS_ERR(vdev))
> return PTR_ERR(vdev);
> @@ -2022,7 +2028,6 @@ static int vduse_dev_init_vdpa(struct vduse_dev *dev,
> const char *name)
> put_device(&vdev->vdpa.dev);
> return ret;
> }
> - set_dma_ops(&vdev->vdpa.dev, &vduse_dev_dma_ops);
> vdev->vdpa.map_token = &vdev->vdpa.dev;
> vdev->vdpa.mdev = &vduse_mgmt->mgmt_dev;
>
> --
> 2.47.3
