[v2] vfio: Implement VFIO_DEVICE_FEATURE_DMA_BUF and use it in virtio-gpu

[PATCH v2 06/10] linux-headers: Update vfio.h to include VFIO_DEVICE_FEATURE_DMA_BUF

Posted by Vivek Kasireddy 5 days, 16 hours ago

Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
---
 linux-headers/linux/vfio.h | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/linux-headers/linux/vfio.h b/linux-headers/linux/vfio.h
index 4d96d1fc12..bc11ca3663 100644
--- a/linux-headers/linux/vfio.h
+++ b/linux-headers/linux/vfio.h
@@ -1478,6 +1478,31 @@ struct vfio_device_feature_bus_master {
 };
 #define VFIO_DEVICE_FEATURE_BUS_MASTER 10
 
+/**
+ * Upon VFIO_DEVICE_FEATURE_GET create a dma_buf fd for the
+ * regions selected.
+ *
+ * open_flags are the typical flags passed to open(2), eg O_RDWR, O_CLOEXEC,
+ * etc. offset/length specify a slice of the region to create the dmabuf from.
+ * nr_ranges is the total number of (P2P DMA) ranges that comprise the dmabuf.
+ *
+ * Return: The fd number on success, -1 and errno is set on failure.
+ */
+#define VFIO_DEVICE_FEATURE_DMA_BUF 11
+
+struct vfio_region_dma_range {
+	__u64 offset;
+	__u64 length;
+};
+
+struct vfio_device_feature_dma_buf {
+	__u32	region_index;
+	__u32	open_flags;
+	__u32   flags;
+	__u32   nr_ranges;
+	struct vfio_region_dma_range dma_ranges[];
+};
+
 /* -------- API for Type1 VFIO IOMMU -------- */
 
 /**
-- 
2.50.1

Re: [PATCH v2 06/10] linux-headers: Update vfio.h to include VFIO_DEVICE_FEATURE_DMA_BUF

Posted by Leon Romanovsky 5 days, 15 hours ago


On Sun, Nov 9, 2025, at 07:33, Vivek Kasireddy wrote:
> Cc: Alex Williamson <alex.williamson@redhat.com>
> Cc: Cédric Le Goater <clg@redhat.com>
> Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
> ---
>  linux-headers/linux/vfio.h | 25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
>
> diff --git a/linux-headers/linux/vfio.h b/linux-headers/linux/vfio.h
> index 4d96d1fc12..bc11ca3663 100644
> --- a/linux-headers/linux/vfio.h
> +++ b/linux-headers/linux/vfio.h
> @@ -1478,6 +1478,31 @@ struct vfio_device_feature_bus_master {
>  };
>  #define VFIO_DEVICE_FEATURE_BUS_MASTER 10
> 
> +/**
> + * Upon VFIO_DEVICE_FEATURE_GET create a dma_buf fd for the
> + * regions selected.
> + *
> + * open_flags are the typical flags passed to open(2), eg O_RDWR, O_CLOEXEC,
> + * etc. offset/length specify a slice of the region to create the dmabuf from.
> + * nr_ranges is the total number of (P2P DMA) ranges that comprise the dmabuf.
> + *
> + * Return: The fd number on success, -1 and errno is set on failure.
> + */
> +#define VFIO_DEVICE_FEATURE_DMA_BUF 11
> +
> +struct vfio_region_dma_range {
> +	__u64 offset;
> +	__u64 length;
> +};
> +
> +struct vfio_device_feature_dma_buf {
> +	__u32	region_index;
> +	__u32	open_flags;
> +	__u32   flags;
> +	__u32   nr_ranges;
> +	struct vfio_region_dma_range dma_ranges[];

Not important comment at all, but in last versions of UAPI, this line is
struct vfio_region_dma_range dma_ranges[] __counted_by(nr_ranges);
https://lore.kernel.org/kvm/20251106-dmabuf-vfio-v7-10-2503bf390699@nvidia.com/T/#Z2e.:..:20251106-dmabuf-vfio-v7-10-2503bf390699::40nvidia.com:1include:uapi:linux:vfio.h

> +};
> +
>  /* -------- API for Type1 VFIO IOMMU -------- */
> 
>  /**
> -- 
> 2.50.1