Re: [RFC PATCH v5 06/11] VFIO_PLATFORM: Return info for device and its memory mapped IO regions

[Alex Williamson <alex.williamson-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

On Mon, 2014-04-28 at 17:52 +0200, Antonios Motakis wrote:
> A VFIO userspace driver will start by opening the VFIO device
> that corresponds to an IOMMU group, and will use the ioctl interface
> to get the basic device info, such as number of memory regions and
> interrupts, and their properties.
> 
> This patch enables the IOCTLs:
>  - VFIO_DEVICE_GET_INFO
>  - VFIO_DEVICE_GET_REGION_INFO
> 
>  IRQ info is provided by one of the latter patches.
> 
> Signed-off-by: Antonios Motakis <a.motakis-lrHrjnjw1UfHK3s98zE1ajGjJy/sRE9J@public.gmane.org>
> ---
>  drivers/vfio/platform/vfio_platform.c         | 77 ++++++++++++++++++++++++---
>  drivers/vfio/platform/vfio_platform_private.h | 17 ++++++
>  2 files changed, 88 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/vfio/platform/vfio_platform.c b/drivers/vfio/platform/vfio_platform.c
> index 1661746..5430cbe 100644
> --- a/drivers/vfio/platform/vfio_platform.c
> +++ b/drivers/vfio/platform/vfio_platform.c
> @@ -34,15 +34,62 @@
>  #define DRIVER_AUTHOR   "Antonios Motakis <a.motakis-lrHrjnjw1UfHK3s98zE1ajGjJy/sRE9J@public.gmane.org>"
>  #define DRIVER_DESC     "VFIO for platform devices - User Level meta-driver"
>  
> +static int vfio_platform_regions_init(struct vfio_platform_device *vdev)
> +{
> +	int cnt = 0, i;
> +
> +	while (platform_get_resource(vdev->pdev, IORESOURCE_MEM, cnt))
> +		cnt++;
> +
> +	vdev->num_regions = cnt;
> +
> +	vdev->region = kzalloc(sizeof(struct vfio_platform_region) * cnt,
> +				GFP_KERNEL);
> +	if (!vdev->region)

Should vdev->num_regions be cleared here or set at the end to avoid
possibly walking a null pointer later?

> +		return -ENOMEM;
> +
> +	for (i = 0; i < cnt;  i++) {
> +		struct vfio_platform_region region;
> +		struct resource *res =
> +			platform_get_resource(vdev->pdev, IORESOURCE_MEM, i);
> +
> +		region.addr = res->start;
> +		region.size = resource_size(res);
> +		region.flags = 0;
> +
> +		vdev->region[i] = region;

nit, the local variable with copy at the end seems rather unnecessary
here.

> +	}
> +
> +	return 0;
> +}
> +
> +static void vfio_platform_regions_cleanup(struct vfio_platform_device *vdev)
> +{
> +	kfree(vdev->region);

Makes me nervous again that we have vdev->num_regions still set to a
value.  Maybe just paranoia.

> +}
> +
>  static void vfio_platform_release(void *device_data)
>  {
> +	struct vfio_platform_device *vdev = device_data;
> +
> +	vfio_platform_regions_cleanup(vdev);
> +
>  	module_put(THIS_MODULE);
>  }
>  
>  static int vfio_platform_open(void *device_data)
>  {
> -	if (!try_module_get(THIS_MODULE))
> +	struct vfio_platform_device *vdev = device_data;
> +	int ret;
> +
> +	ret = vfio_platform_regions_init(vdev);
> +	if (ret)
> +		return ret;
> +
> +	if (!try_module_get(THIS_MODULE)) {
> +		vfio_platform_regions_cleanup(vdev);
>  		return -ENODEV;
> +	}

Getting a reference to the module seems like it should be step 1 here.
Thanks,

Alex

>  
>  	return 0;
>  }
> @@ -65,18 +112,36 @@ static long vfio_platform_ioctl(void *device_data,
>  			return -EINVAL;
>  
>  		info.flags = VFIO_DEVICE_FLAGS_PLATFORM;
> -		info.num_regions = 0;
> +		info.num_regions = vdev->num_regions;
>  		info.num_irqs = 0;
>  
>  		return copy_to_user((void __user *)arg, &info, minsz);
>  
> -	} else if (cmd == VFIO_DEVICE_GET_REGION_INFO)
> -		return -EINVAL;
> +	} else if (cmd == VFIO_DEVICE_GET_REGION_INFO) {
> +		struct vfio_region_info info;
> +
> +		minsz = offsetofend(struct vfio_region_info, offset);
> +
> +		if (copy_from_user(&info, (void __user *)arg, minsz))
> +			return -EFAULT;
> +
> +		if (info.argsz < minsz)
> +			return -EINVAL;
> +
> +		if (info.index >= vdev->num_regions)
> +			return -EINVAL;
> +
> +		/* map offset to the physical address  */
> +		info.offset = VFIO_PLATFORM_INDEX_TO_OFFSET(info.index);
> +		info.size = vdev->region[info.index].size;
> +		info.flags = vdev->region[info.index].flags;
> +
> +		return copy_to_user((void __user *)arg, &info, minsz);
>  
> -	else if (cmd == VFIO_DEVICE_GET_IRQ_INFO)
> +	} else if (cmd == VFIO_DEVICE_GET_IRQ_INFO) {
>  		return -EINVAL;
>  
> -	else if (cmd == VFIO_DEVICE_SET_IRQS)
> +	} else if (cmd == VFIO_DEVICE_SET_IRQS)
>  		return -EINVAL;
>  
>  	else if (cmd == VFIO_DEVICE_RESET)
> diff --git a/drivers/vfio/platform/vfio_platform_private.h b/drivers/vfio/platform/vfio_platform_private.h
> index 4ae88f8..3448f918 100644
> --- a/drivers/vfio/platform/vfio_platform_private.h
> +++ b/drivers/vfio/platform/vfio_platform_private.h
> @@ -15,8 +15,25 @@
>  #ifndef VFIO_PLATFORM_PRIVATE_H
>  #define VFIO_PLATFORM_PRIVATE_H
>  
> +#define VFIO_PLATFORM_OFFSET_SHIFT   40
> +#define VFIO_PLATFORM_OFFSET_MASK (((u64)(1) << VFIO_PLATFORM_OFFSET_SHIFT) - 1)
> +
> +#define VFIO_PLATFORM_OFFSET_TO_INDEX(off)	\
> +	(off >> VFIO_PLATFORM_OFFSET_SHIFT)
> +
> +#define VFIO_PLATFORM_INDEX_TO_OFFSET(index)	\
> +	((u64)(index) << VFIO_PLATFORM_OFFSET_SHIFT)
> +
> +struct vfio_platform_region {
> +	u64			addr;
> +	resource_size_t		size;
> +	u32			flags;
> +};
> +
>  struct vfio_platform_device {
>  	struct platform_device		*pdev;
> +	struct vfio_platform_region	*region;
> +	u32				num_regions;
>  };
>  
>  #endif /* VFIO_PLATFORM_PRIVATE_H */