On Wed, Jun 10, 2026 at 04:43:19PM +0100, Matt Evans wrote:
> Since converting BAR mmap()s to using DMABUFs, we lose the original
> device path in /proc/<pid>/maps, lsof, etc. Generate a debug-oriented
> synthetic 'filename' based on the cdev, plus BDF, plus resource index.
>
> This applies only to BAR mappings via the VFIO device fd, as
> explicitly-exported DMABUFs are named by userspace via the
> DMA_BUF_SET_NAME ioctl.
>
> Signed-off-by: Matt Evans <[email protected]>
> ---
> drivers/vfio/pci/vfio_pci_dmabuf.c | 27 +++++++++++++++++++++++++--
> 1 file changed, 25 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/vfio/pci/vfio_pci_dmabuf.c
> b/drivers/vfio/pci/vfio_pci_dmabuf.c
> index 2fd3629789bf..8f7f1b909b94 100644
> --- a/drivers/vfio/pci/vfio_pci_dmabuf.c
> +++ b/drivers/vfio/pci/vfio_pci_dmabuf.c
> @@ -4,6 +4,7 @@
> #include <linux/dma-buf-mapping.h>
> #include <linux/pci-p2pdma.h>
> #include <linux/dma-resv.h>
> +#include <uapi/linux/dma-buf.h>
>
> #include "vfio_pci_priv.h"
>
> @@ -470,6 +471,7 @@ int vfio_pci_core_mmap_prep_dmabuf(struct
> vfio_pci_core_device *vdev,
> {
> struct vfio_pci_dma_buf *priv;
> unsigned long vma_pgoff = vma->vm_pgoff & (VFIO_PCI_OFFSET_MASK >>
> PAGE_SHIFT);
> + char *bufname;
> int ret;
>
> priv = kzalloc_obj(*priv);
> @@ -482,6 +484,20 @@ int vfio_pci_core_mmap_prep_dmabuf(struct
> vfio_pci_core_device *vdev,
> goto err_free_priv;
> }
>
> + bufname = kzalloc(DMA_BUF_NAME_LEN, GFP_KERNEL);
> + if (!bufname) {
> + ret = -ENOMEM;
> + goto err_free_phys;
> + }
> +
> + /*
> + * Maximum size of the friendly debug name is
> + * vfio1234567890:ffff:ff:3f.7/5 = 30, which fits within
> + * DMA_BUF_NAME_LEN.
> + */
> + snprintf(bufname, DMA_BUF_NAME_LEN, "%s:%s/%x",
> + dev_name(&vdev->vdev.device), pci_name(vdev->pdev), res_index);
> +
Nit: Could we instead use:
bufname = kasprintf(GFP_KERNEL, "%s:%s/%x",
dev_name(&vdev->vdev.device), pci_name(vdev->pdev),
res_index);
if (!bufname)
ret = -ENOMEM;
[...]
> /*
> * The DMABUF begins from the mmap()'s BAR offset, i.e. the
> * start of the VMA corresponds to byte 0 of the DMABUF and
> @@ -500,7 +516,7 @@ int vfio_pci_core_mmap_prep_dmabuf(struct
> vfio_pci_core_device *vdev,
> priv->provider = pcim_p2pdma_provider(vdev->pdev, res_index);
> if (!priv->provider) {
> ret = -EINVAL;
> - goto err_free_phys;
> + goto err_free_name;
> }
>
> priv->phys_vec[0].paddr = phys_start + ((u64)vma_pgoff << PAGE_SHIFT);
> @@ -508,7 +524,7 @@ int vfio_pci_core_mmap_prep_dmabuf(struct
> vfio_pci_core_device *vdev,
>
> ret = vfio_pci_dmabuf_export(vdev, priv, O_CLOEXEC | O_RDWR);
> if (ret)
> - goto err_free_phys;
> + goto err_free_name;
>
> /*
> * Ownership of the DMABUF file transfers to the VMA so that
> @@ -523,8 +539,15 @@ int vfio_pci_core_mmap_prep_dmabuf(struct
> vfio_pci_core_device *vdev,
> vma->vm_file = priv->dmabuf->file;
> vma->vm_private_data = priv;
>
> + spin_lock(&priv->dmabuf->name_lock);
> + kfree(priv->dmabuf->name);
> + priv->dmabuf->name = bufname;
> + spin_unlock(&priv->dmabuf->name_lock);
> +
> return 0;
>
> +err_free_name:
> + kfree(bufname);
> err_free_phys:
> kfree(priv->phys_vec);
> err_free_priv:
Apart from that,
Reviewed-by: Pranjal Shrivastava <[email protected]>
Thanks,
Praan
