Re: [PATCH v2 5/5] drm/i915/gvt: Adding interface so user space can get the dma-buf

[Alex Williamson]

On Thu, 18 May 2017 17:50:05 +0800
Xiaoguang Chen <xiaoguang.chen@xxxxxxxxx> wrote:

> User space will try to create a management fd for the dma-buf operation.
> Using this management fd user can query the plane information and create
> a dma-buf fd if necessary.
> GVT-g will handle the life cycle of the management fd and will align the
> life cycle of the fd with the vfio device.
> User space should handle the life cycle of the created dma-buf fd close
> the dma-buf fd timely when finishing use.
> 
> Signed-off-by: Xiaoguang Chen <xiaoguang.chen@xxxxxxxxx>
> ---
>  drivers/gpu/drm/i915/gvt/gvt.c   |  2 +
>  drivers/gpu/drm/i915/gvt/gvt.h   |  3 ++
>  drivers/gpu/drm/i915/gvt/kvmgt.c | 89 ++++++++++++++++++++++++++++++++++++++++
>  include/uapi/drm/i915_drm.h      |  2 +
>  include/uapi/linux/vfio.h        | 12 ++++++
>  5 files changed, 108 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/gvt/gvt.c b/drivers/gpu/drm/i915/gvt/gvt.c
> index 2032917..48e04e6 100644
> --- a/drivers/gpu/drm/i915/gvt/gvt.c
> +++ b/drivers/gpu/drm/i915/gvt/gvt.c
> @@ -54,6 +54,8 @@
>  	.vgpu_reset = intel_gvt_reset_vgpu,
>  	.vgpu_activate = intel_gvt_activate_vgpu,
>  	.vgpu_deactivate = intel_gvt_deactivate_vgpu,
> +	.vgpu_query_dmabuf = intel_vgpu_query_dmabuf,
> +	.vgpu_create_dmabuf = intel_vgpu_create_dmabuf,
>  };
>  
>  /**
> diff --git a/drivers/gpu/drm/i915/gvt/gvt.h b/drivers/gpu/drm/i915/gvt/gvt.h
> index a553120..b7fdfd5 100644
> --- a/drivers/gpu/drm/i915/gvt/gvt.h
> +++ b/drivers/gpu/drm/i915/gvt/gvt.h
> @@ -185,6 +185,7 @@ struct intel_vgpu {
>  		struct kvm *kvm;
>  		struct work_struct release_work;
>  		atomic_t released;
> +		struct vfio_device *vfio_device;
>  	} vdev;
>  #endif
>  	struct intel_vgpu_plane_info *plane_info;
> @@ -469,6 +470,8 @@ struct intel_gvt_ops {
>  	void (*vgpu_reset)(struct intel_vgpu *);
>  	void (*vgpu_activate)(struct intel_vgpu *);
>  	void (*vgpu_deactivate)(struct intel_vgpu *);
> +	int (*vgpu_query_dmabuf)(struct intel_vgpu *, void *);
> +	int (*vgpu_create_dmabuf)(struct intel_vgpu *, void *);
>  };
>  
>  
> diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
> index 389f072..9a663df 100644
> --- a/drivers/gpu/drm/i915/gvt/kvmgt.c
> +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
> @@ -41,6 +41,7 @@
>  #include <linux/kvm_host.h>
>  #include <linux/vfio.h>
>  #include <linux/mdev.h>
> +#include <linux/anon_inodes.h>
>  
>  #include "i915_drv.h"
>  #include "gvt.h"
> @@ -524,6 +525,66 @@ static int intel_vgpu_reg_init_opregion(struct intel_vgpu *vgpu)
>  	return ret;
>  }
>  
> +static int intel_vgpu_dmabuf_mgr_fd_mmap(struct file *file,
> +		struct vm_area_struct *vma)
> +{
> +	return -EPERM;
> +}
> +
> +static int intel_vgpu_dmabuf_mgr_fd_release(struct inode *inode,
> +		struct file *filp)
> +{
> +	struct intel_vgpu *vgpu = filp->private_data;
> +
> +	if (vgpu->vdev.vfio_device != NULL)
> +		vfio_device_put(vgpu->vdev.vfio_device);
> +	else
> +		gvt_vgpu_err("intel vgpu dmabuf mgr fd is in a wrong state\n");

You could do:

if (WARN_ON(!vgpu->vdev.vfio_device))
	return -EINVAL;

> +
> +	return 0;
> +}
> +
> +static long intel_vgpu_dmabuf_mgr_fd_ioctl(struct file *filp,
> +		unsigned int ioctl, unsigned long arg)
> +{
> +	struct intel_vgpu *vgpu = filp->private_data;
> +	int minsz;
> +	struct intel_vgpu_dmabuf dmabuf;
> +	int ret;
> +	struct fd f;
> +
> +	minsz = offsetofend(struct intel_vgpu_dmabuf, tiled);
> +	if (copy_from_user(&dmabuf, (void __user *)arg, minsz))
> +		return -EFAULT;
> +
> +	f = fdget(dmabuf.fd);
> +
> +	if (ioctl == INTEL_VGPU_QUERY_DMABUF)
> +		ret = intel_gvt_ops->vgpu_query_dmabuf(vgpu, &dmabuf);
> +	else if (ioctl == INTEL_VGPU_GENERATE_DMABUF)
> +		ret = intel_gvt_ops->vgpu_create_dmabuf(vgpu, &dmabuf);

Why are these still Intel specific?

> +	else {
> +		fdput(f);
> +		gvt_vgpu_err("unsupported dmabuf operation\n");
> +		return -EINVAL;
> +	}
> +
> +	if (ret != 0) {
> +		fdput(f);
> +		gvt_vgpu_err("gvt-g get dmabuf failed:%d\n", ret);
> +		return -EINVAL;
> +	}
> +	fdput(f);
> +
> +	return copy_to_user((void __user *)arg, &dmabuf, minsz) ? -EFAULT : 0;
> +}
> +
> +static const struct file_operations intel_vgpu_dmabuf_mgr_fd_ops = {
> +	.release        = intel_vgpu_dmabuf_mgr_fd_release,
> +	.unlocked_ioctl = intel_vgpu_dmabuf_mgr_fd_ioctl,
> +	.mmap           = intel_vgpu_dmabuf_mgr_fd_mmap,
> +	.llseek         = noop_llseek,
> +};
>  static int intel_vgpu_create(struct kobject *kobj, struct mdev_device *mdev)
>  {
>  	struct intel_vgpu *vgpu = NULL;
> @@ -1259,6 +1320,34 @@ static long intel_vgpu_ioctl(struct mdev_device *mdev, unsigned int cmd,
>  	} else if (cmd == VFIO_DEVICE_RESET) {
>  		intel_gvt_ops->vgpu_reset(vgpu);
>  		return 0;
> +	} else if (cmd == VFIO_DEVICE_GET_FD) {
> +		int fd;
> +		u32 type;
> +		struct vfio_device *device;
> +
> +		if (copy_from_user(&type, (void __user *)arg, sizeof(type)))
> +			return -EINVAL;
> +		if (type != INTEL_VGPU_DMABUF_MGR_FD) {

Yet more unnecessary Intel specific code.  Userspace doesn't want to
handle a dmabuf differently between Intel, AMD, and NVIDIA, so if we
have no reason to need vendor specific ioctl and parameters, then don't.

> +			gvt_vgpu_err("not supported fd type:%d\n", type);

Just return error, users can abuse any logging they can get to.

> +			return -EINVAL;
> +		}
> +
> +		fd = anon_inode_getfd("intel-vgpu-dmabuf-mgr-fd",
> +			&intel_vgpu_dmabuf_mgr_fd_ops,
> +			vgpu, O_RDWR | O_CLOEXEC);

And this ordering is still wrong, do this last so you don't need to
worry about getting the vfio_device reference below failing and calling
release unnecessarily (though it seems this fd is leaked in that case
anyway).

> +		if (fd < 0) {
> +			gvt_vgpu_err("create dmabuf mgr fd failed\n");
> +			return -EINVAL;
> +		}
> +
> +		device = vfio_device_get_from_dev(mdev_dev(mdev));
> +		if (device == NULL) {
> +			gvt_vgpu_err("kvmgt: vfio device is null\n");
> +			return -EINVAL;
> +		}
> +		vgpu->vdev.vfio_device = device;
> +
> +		return fd;
>  	}
>  
>  	return 0;
> diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
> index cde4f8e..9d28433 100644
> --- a/include/uapi/drm/i915_drm.h
> +++ b/include/uapi/drm/i915_drm.h
> @@ -1466,6 +1466,8 @@ struct intel_vgpu_dmabuf {
>  	__u32 tiled;
>  };
>  
> +#define INTEL_VGPU_DMABUF_MGR_FD	0
> +
>  #if defined(__cplusplus)
>  }
>  #endif
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index ae46105..c81500b 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -502,6 +502,18 @@ 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)
> +

The known input types would need to be defined here too.  Definition of
the ioctls available on that type should also be documented here.

>  /* -------- API for Type1 VFIO IOMMU -------- */
>  
>  /**