Re: [PATCH v19 12/18] vfio/pci: Add dmabuf TPH metadata storage and fd query helper

[Alex Williamson <alex@shazbot.org>]

On Thu, 2 Jul 2026 20:42:18 +0800
Chengwen Feng <fengchengwen@huawei.com> wrote:

> Add TPH metadata fields to struct vfio_pci_dma_buf to store PH,
> basic/extended ST and their validity flags.
> 
> Implement vfio_pci_dma_buf_get_pci_tph() to fetch TPH tag and PH from
> dmabuf, distinguish basic and extended ST namespace.
> 
> Add vfio_pci_dma_buf_get_tph_by_fd() to resolve TPH data via dmabuf fd,
> validate dmabuf owner ops. Provide stub implementation if
> CONFIG_VFIO_PCI_DMABUF is unset.
> 
> Lay dmabuf foundation for the upcoming TPH_RESOLVE feature.
> 
> Signed-off-by: Zhiping Zhang <zhipingz@meta.com>
> Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
> ---
>  drivers/vfio/pci/vfio_pci_dmabuf.c | 49 +++++++++++++++++++++++++++++-
>  drivers/vfio/pci/vfio_pci_priv.h   |  6 ++++
>  2 files changed, 54 insertions(+), 1 deletion(-)

Please don't send competing patches, just indicate the series is based
on Zhiping's series v#.  This makes all the naming changes that Zhiping
declined yet you still included their sign-off.  Thanks,

Alex

> 
> diff --git a/drivers/vfio/pci/vfio_pci_dmabuf.c b/drivers/vfio/pci/vfio_pci_dmabuf.c
> index c16f460c01d6..d9c5e434e586 100644
> --- a/drivers/vfio/pci/vfio_pci_dmabuf.c
> +++ b/drivers/vfio/pci/vfio_pci_dmabuf.c
> @@ -19,7 +19,14 @@ struct vfio_pci_dma_buf {
>  	u32 nr_ranges;
>  	struct kref kref;
>  	struct completion comp;
> -	u8 revoked : 1;
> +
> +	/* Protected by dmabuf->resv. */
> +	u8 revoked:1;
> +	u8 tph_ph:2;
> +	u8 tph_st_valid:1;
> +	u8 tph_xst_valid:1;
> +	u8 tph_st;
> +	u16 tph_xst;
>  };
>  
>  static int vfio_pci_dma_buf_attach(struct dma_buf *dmabuf,
> @@ -81,6 +88,26 @@ static void vfio_pci_dma_buf_unmap(struct dma_buf_attachment *attachment,
>  	kref_put(&priv->kref, vfio_pci_dma_buf_done);
>  }
>  
> +static int vfio_pci_dma_buf_get_pci_tph(struct dma_buf *dmabuf, bool extended,
> +					u16 *tag, u8 *ph)
> +{
> +	struct vfio_pci_dma_buf *priv = dmabuf->priv;
> +
> +	dma_resv_assert_held(priv->dmabuf->resv);
> +
> +	if (extended) {
> +		if (!priv->tph_xst_valid)
> +			return -EOPNOTSUPP;
> +		*tag = priv->tph_xst;
> +	} else {
> +		if (!priv->tph_st_valid)
> +			return -EOPNOTSUPP;
> +		*tag = priv->tph_st;
> +	}
> +	*ph = priv->tph_ph;
> +	return 0;
> +}
> +
>  static void vfio_pci_dma_buf_release(struct dma_buf *dmabuf)
>  {
>  	struct vfio_pci_dma_buf *priv = dmabuf->priv;
> @@ -106,6 +133,26 @@ static const struct dma_buf_ops vfio_pci_dmabuf_ops = {
>  	.release = vfio_pci_dma_buf_release,
>  };
>  
> +int vfio_pci_dma_buf_get_tph_by_fd(int fd, bool extended, u16 *tag, u8 *ph)
> +{
> +	struct dma_buf *dmabuf;
> +	int ret = 0;
> +
> +	dmabuf = dma_buf_get(fd);
> +	if (IS_ERR(dmabuf))
> +		return PTR_ERR(dmabuf);
> +
> +	if (dmabuf->ops != &vfio_pci_dmabuf_ops) {
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +	ret = vfio_pci_dma_buf_get_pci_tph(dmabuf, extended, tag, ph);
> +out:
> +	dma_buf_put(dmabuf);
> +	return ret;
> +}
> +
>  /*
>   * This is a temporary "private interconnect" between VFIO DMABUF and iommufd.
>   * It allows the two co-operating drivers to exchange the physical address of
> diff --git a/drivers/vfio/pci/vfio_pci_priv.h b/drivers/vfio/pci/vfio_pci_priv.h
> index c997cc9bf330..d7bc52f488c6 100644
> --- a/drivers/vfio/pci/vfio_pci_priv.h
> +++ b/drivers/vfio/pci/vfio_pci_priv.h
> @@ -122,12 +122,18 @@ static inline bool vfio_pci_is_vga(struct pci_dev *pdev)
>  }
>  
>  #ifdef CONFIG_VFIO_PCI_DMABUF
> +int vfio_pci_dma_buf_get_tph_by_fd(int fd, bool extended, u16 *tag, u8 *ph);
>  int vfio_pci_core_feature_dma_buf(struct vfio_pci_core_device *vdev, u32 flags,
>  				  struct vfio_device_feature_dma_buf __user *arg,
>  				  size_t argsz);
>  void vfio_pci_dma_buf_cleanup(struct vfio_pci_core_device *vdev);
>  void vfio_pci_dma_buf_move(struct vfio_pci_core_device *vdev, bool revoked);
>  #else
> +static inline int vfio_pci_dma_buf_get_tph_by_fd(int fd, bool extended,
> +						 u16 *tag, u8 *ph)
> +{
> +	return -EOPNOTSUPP;
> +}
>  static inline int
>  vfio_pci_core_feature_dma_buf(struct vfio_pci_core_device *vdev, u32 flags,
>  			      struct vfio_device_feature_dma_buf __user *arg,