linux-kernel - Re: [PATCH v9 5/7] vfio: Define vfio based dma-buf operations

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Date:   Thu, 15 Jun 2017 20:21:53 +0530
From:   Kirti Wankhede <kwankhede@...dia.com>
To:     Xiaoguang Chen <xiaoguang.chen@...el.com>,
        <alex.williamson@...hat.com>, <kraxel@...hat.com>,
        <chris@...is-wilson.co.uk>, <intel-gfx@...ts.freedesktop.org>,
        <linux-kernel@...r.kernel.org>, <zhenyuw@...ux.intel.com>,
        <zhiyuan.lv@...el.com>, <intel-gvt-dev@...ts.freedesktop.org>,
        <zhi.a.wang@...el.com>, <kevin.tian@...el.com>
Subject: Re: [PATCH v9 5/7] vfio: Define vfio based dma-buf operations



On 6/15/2017 1:30 PM, Xiaoguang Chen wrote:
> Here we defined a new ioctl to create a fd for a vfio device based on
> the input type. Now only one type is supported that is a dma-buf
> management fd.
> Two ioctls are defined for the dma-buf management fd: query the vfio
> vgpu's plane information and create a dma-buf for a plane.
> 

I had suggested how we can use common structures for both type of ways
to query surface on v6 version of your patch,
https://lkml.org/lkml/2017/6/1/890


> Signed-off-by: Xiaoguang Chen <xiaoguang.chen@...el.com>
> ---
>  include/uapi/linux/vfio.h | 57 +++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 57 insertions(+)
> 
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index ae46105..7d86101 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -502,6 +502,63 @@ struct vfio_pci_hot_reset {
>  
>  #define VFIO_DEVICE_PCI_HOT_RESET	_IO(VFIO_TYPE, VFIO_BASE + 13)
>  
> +/**
> + * VFIO_DEVICE_GET_FD - _IO(VFIO_TYPE, VFIO_BASE + 14, __u32)
> + *
> + * Create a fd for a vfio device based on the input type
> + * Vendor driver should handle this ioctl to create a fd and manage the
> + * life cycle of this fd.
> + *
> + * Return: a fd if vendor support that type, -errno if not supported
> + */
> +
> +#define VFIO_DEVICE_GET_FD	_IO(VFIO_TYPE, VFIO_BASE + 14)
> +
> +#define VFIO_DEVICE_DMABUF_MGR_FD	0 /* Supported fd types */
> +
> +struct vfio_dmabuf_mgr_plane_info {
> +	__u64 start;
> +	__u64 drm_format_mod;
> +	__u32 drm_format;
> +	__u32 width;
> +	__u32 height;
> +	__u32 stride;
> +	__u32 size;
> +	__u32 x_pos;
> +	__u32 y_pos;
> +	__u32 padding;
> +};
> +

This structure is generic, can remove dmabuf from its name,
vfio_plane_info or vfio_vgpu_surface_info since this will only be used
by vgpu.

> +/*
> + * VFIO_DMABUF_MGR_QUERY_PLANE - _IO(VFIO_TYPE, VFIO_BASE + 15,
> + *					struct vfio_dmabuf_mgr_query_plane)
> + * Query plane information
> + */
> +struct vfio_dmabuf_mgr_query_plane {
> +	__u32 argsz;
> +	__u32 flags;
> +	struct vfio_dmabuf_mgr_plane_info plane_info;
> +	__u32 plane_id;
> +};
> +
> +#define VFIO_DMABUF_MGR_QUERY_PLANE _IO(VFIO_TYPE, VFIO_BASE + 15)
> +

This same interface can be used to query surface/plane information for
both, dmabuf and region, case. Here also 'DMABUF' can be removed and
define flags if you want to differentiate query for 'dmabuf' and 'region'.

Thanks,
Kirti

> +/*
> + * VFIO_DMABUF_MGR_CREATE_DMABUF - _IO(VFIO, VFIO_BASE + 16,
> + *					struct vfio_dmabuf_mgr_create_dmabuf)
> + *
> + * Create a dma-buf for a plane
> + */
> +struct vfio_dmabuf_mgr_create_dmabuf {
> +	__u32 argsz;
> +	__u32 flags;
> +	struct vfio_dmabuf_mgr_plane_info plane_info;
> +	__u32 plane_id;
> +	__s32 fd;
> +};
> +
> +#define VFIO_DMABUF_MGR_CREATE_DMABUF _IO(VFIO_TYPE, VFIO_BASE + 16)
> +
>  /* -------- API for Type1 VFIO IOMMU -------- */
>  /**
>