[Linaro-mm-sig] Re: [RFC v2 4/8] vfio/pci/dmabuf: Add support for IOV interconnect

Hi Matt,

Subject: Re: [RFC v2 4/8] vfio/pci/dmabuf: Add support for IOV interconnect

On Sun, Oct 26, 2025 at 09:44:16PM -0700, Vivek Kasireddy wrote:

...

Add support for IOV interconnect by provding ops for map/unmap and match interconnect. Note that the xarray is populated with entries of type struct range. The range type contains the start and end addresses of the memory region.

Cc: Jason Gunthorpe jgg@nvidia.com Cc: Christian Koenig christian.koenig@amd.com Cc: Sumit Semwal sumit.semwal@linaro.org Cc: Thomas Hellström thomas.hellstrom@linux.intel.com Cc: Simona Vetter simona.vetter@ffwll.ch Signed-off-by: Vivek Kasireddy vivek.kasireddy@intel.com

---

drivers/vfio/pci/vfio_pci_dmabuf.c | 135

++++++++++++++++++++++++++++-

...

1 file changed, 134 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/pci/vfio_pci_dmabuf.c

b/drivers/vfio/pci/vfio_pci_dmabuf.c

...

index eaba010777f3..d2b7b5410e5a 100644 --- a/drivers/vfio/pci/vfio_pci_dmabuf.c +++ b/drivers/vfio/pci/vfio_pci_dmabuf.c

In drm-tip vfio_pci_dmabuf.c does not exist as a file? Is this series based on another series / branch where vfio_pci_dmabuf.c hasn't made it into drm-tip yet?

That file is part of [1] which hasn't been merged yet. The last patch in [1] adds the dmabuf feature to vfio-pci.

[1]: https://lore.kernel.org/dri-devel/cover.1760368250.git.leon@kernel.org/

Thanks, Vivek

Matt

...

@@ -4,6 +4,7 @@ #include <linux/dma-buf.h> #include <linux/pci-p2pdma.h> #include <linux/dma-resv.h> +#include <linux/range.h>

#include "vfio_pci_priv.h"

@@ -16,15 +17,132 @@ struct vfio_pci_dma_buf { size_t size; struct phys_vec *phys_vec; struct p2pdma_provider *provider;

• struct dma_buf_interconnect_match *ic_match; u32 nr_ranges; u8 revoked : 1;

};

+static int +vfio_pci_create_match(struct vfio_pci_dma_buf *priv,

• 	  struct vfio_device_feature_dma_buf *dma_buf)
  

+{

• struct dma_buf_interconnect_match *ic_match;
• ic_match = kzalloc(sizeof(*ic_match), GFP_KERNEL);
• if (!ic_match)

• return -ENOMEM;
  

• ic_match->dev = &priv->vdev->pdev->dev;
• ic_match->bar = dma_buf->region_index;
• priv->ic_match = ic_match;
• return 0;

+}

+static int vfio_pci_map_iov_interconnect(struct vfio_pci_dma_buf *priv,

• 			 struct xarray *ranges)
  

+{

• struct phys_vec *phys_vec = priv->phys_vec;
• struct range *range;
• unsigned long i;
• void *entry;
• int ret;
• range = kmalloc_array(priv->nr_ranges, sizeof(*range), GFP_KERNEL);
• if (!range)

• return -ENOMEM;
  

• for (i = 0; i < priv->nr_ranges; i++) {

• entry = &range[i];
  

• range[i].start = phys_vec[i].paddr;
  

• range[i].end = phys_vec[i].paddr + phys_vec[i].len - 1;
  

• entry = xa_store(ranges, i, entry, GFP_KERNEL);
  

• if (xa_is_err(entry)) {
  

• 	ret = xa_err(entry);
  

• 	goto err_free_range;
  

• }
  

• }
• return 0;

+err_free_range:

• kfree(range);
• return ret;

+}

+static int vfio_pci_map_interconnect(struct dma_buf_attachment

*attachment,

...

• 		     struct dma_buf_ranges *ranges)
  

+{

• const struct dma_buf_interconnect *ic = attachment->ic_match->type;
• struct vfio_pci_dma_buf *priv = attachment->dmabuf->priv;
• int ret = -EINVAL;
• ranges->nranges = priv->nr_ranges;
• if (ic == iov_interconnect)

• ret = vfio_pci_map_iov_interconnect(priv, &ranges->ranges);
  

• return ret;

+}

+static void vfio_pci_unmap_interconnect(struct dma_buf_attachment

*attachment,

...

• 			struct dma_buf_ranges *ranges)
  

+{

• void *entry;
• entry = xa_load(&ranges->ranges, 0);
• kfree(entry);

+}

+static bool +vfio_pci_match_iov_interconnect(const struct

dma_buf_interconnect_match *exp,

...

• 		const struct dma_buf_interconnect_match
  

*imp)

...

+{

• struct pci_dev *exp_pdev = to_pci_dev(exp->dev);
• struct pci_dev *imp_pdev = to_pci_dev(imp->dev);
• return imp_pdev == pci_physfn(exp_pdev) && imp->bar == exp->bar;

+}

+static bool +vfio_pci_match_interconnect(const struct dma_buf_interconnect_match

*exp,

...

• 	    const struct dma_buf_interconnect_match *imp)
  

+{

• const struct dma_buf_interconnect *ic = exp->type;
• if (ic == iov_interconnect)

• return vfio_pci_match_iov_interconnect(exp, imp);
  

• return false;

+}

+static bool +vfio_pci_match_interconnects(struct vfio_pci_dma_buf *priv,

• 	     struct dma_buf_attachment *attachment)
  

+{

• const struct dma_buf_attach_ops *aops = attachment->importer_ops;
• const struct dma_buf_interconnect_match supports_ics[] = {

• MATCH_INTERCONNECT(iov_interconnect,
  

• 		   priv->ic_match->dev, priv->ic_match->bar),
  

• };
• if (attachment->allow_ic) {

• if (aops->supports_interconnects(attachment, supports_ics,
  

• 				 ARRAY_SIZE(supports_ics)))
  

• 	return true;
  

• }
• return false;

+}

static int vfio_pci_dma_buf_attach(struct dma_buf *dmabuf, struct dma_buf_attachment *attachment) { struct vfio_pci_dma_buf *priv = dmabuf->priv;

• if (vfio_pci_match_interconnects(priv, attachment)) {

• return 0;
  

• }
• if (!attachment->peer2peer) return -EOPNOTSUPP;

@@ -189,6 +307,7 @@ vfio_pci_dma_buf_map(struct dma_buf_attachment

*attachment,

...

return ERR_PTR(ret); }

static void vfio_pci_dma_buf_unmap(struct dma_buf_attachment

*attachment,

...

		   struct sg_table *sgt,
		   enum dma_data_direction dir)

@@ -228,15 +347,23 @@ static void vfio_pci_dma_buf_release(struct

dma_buf *dmabuf)

...

vfio_device_put_registration(&priv->vdev->vdev);

} kfree(priv->phys_vec);

• kfree(priv->ic_match); kfree(priv);

}

+static const struct dma_buf_interconnect_ops vfio_pci_interconnect_ops =

{

...

• .match_interconnect = vfio_pci_match_interconnect,
• .map_interconnect = vfio_pci_map_interconnect,
• .unmap_interconnect = vfio_pci_unmap_interconnect,

+};

static const struct dma_buf_ops vfio_pci_dmabuf_ops = { .attach = vfio_pci_dma_buf_attach, .detach = vfio_pci_dma_buf_detach, .map_dma_buf = vfio_pci_dma_buf_map, .release = vfio_pci_dma_buf_release, .unmap_dma_buf = vfio_pci_dma_buf_unmap,

• .interconnect_ops = &vfio_pci_interconnect_ops,

};

static void dma_ranges_to_p2p_phys(struct vfio_pci_dma_buf *priv, @@ -365,6 +492,10 @@ int vfio_pci_core_feature_dma_buf(struct

vfio_pci_core_device *vdev, u32 flags,

...

goto err_free_phys;

}

• ret = vfio_pci_create_match(priv, &get_dma_buf);
• if (ret)

• goto err_dev_put;
  

• exp_info.ops = &vfio_pci_dmabuf_ops; exp_info.size = priv->size; exp_info.flags = get_dma_buf.open_flags;

@@ -373,7 +504,7 @@ int vfio_pci_core_feature_dma_buf(struct

vfio_pci_core_device *vdev, u32 flags,

...

priv->dmabuf = dma_buf_export(&exp_info); if (IS_ERR(priv->dmabuf)) { ret = PTR_ERR(priv->dmabuf);

• goto err_dev_put;
  

• goto err_free_iov;
  

  }

  /* dma_buf_put() now frees priv */

@@ -391,6 +522,8 @@ int vfio_pci_core_feature_dma_buf(struct

vfio_pci_core_device *vdev, u32 flags,

...

*/

return dma_buf_fd(priv->dmabuf, get_dma_buf.open_flags);

+err_free_iov:

• kfree(priv->ic_match);

err_dev_put: vfio_device_put_registration(&vdev->vdev); err_free_phys: -- 2.50.1