[PATCH] drm/amd/amdgpu: Partial revert of iova debugfs

[Christian König]

Am 20.09.2017 um 13:42 schrieb Tom St Denis:
> We discovered that on some devices even with iommu enabled
> you can access all of system memory through the iommu translation.
>
> Therefore, we revert the read method to the translation only service
> and drop the write method completely.
>
> Signed-off-by: Tom St Denis <tom.stdenis at amd.com>

Reviewed-by: Christan König <christian.koenig at amd.com>

> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 90 +++++----------------------------
>   1 file changed, 13 insertions(+), 77 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> index 0e5f78f3a97e..ce435dbbb398 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> @@ -1784,98 +1784,34 @@ static ssize_t amdgpu_iova_to_phys_read(struct file *f, char __user *buf,
>   				   size_t size, loff_t *pos)
>   {
>   	struct amdgpu_device *adev = file_inode(f)->i_private;
> -	ssize_t result, n;
>   	int r;
>   	uint64_t phys;
> -	void *ptr;
>   	struct iommu_domain *dom;
>   
> -	dom = iommu_get_domain_for_dev(adev->dev);
> -	if (!dom)
> -		return -EFAULT;
> -
> -	result = 0;
> -	while (size) {
> -		// get physical address and map
> -		phys = iommu_iova_to_phys(dom, *pos);
> -
> -		// copy upto one page
> -		if (size > PAGE_SIZE)
> -			n = PAGE_SIZE;
> -		else
> -			n = size;
> -
> -		// to end of the page
> -		if (((*pos & (PAGE_SIZE - 1)) + n) >= PAGE_SIZE)
> -			n = PAGE_SIZE - (*pos & (PAGE_SIZE - 1));
> -
> -		ptr = kmap(pfn_to_page(PFN_DOWN(phys)));
> -		if (!ptr)
> -			return -EFAULT;
> -
> -		r = copy_to_user(buf, ptr, n);
> -		kunmap(pfn_to_page(PFN_DOWN(phys)));
> -		if (r)
> -			return -EFAULT;
> -
> -		*pos += n;
> -		size -= n;
> -		result += n;
> -	}
> -
> -	return result;
> -}
> +	// always return 8 bytes
> +	if (size != 8)
> +		return -EINVAL;
>   
> -static ssize_t amdgpu_iova_to_phys_write(struct file *f, const char __user *buf,
> -				   size_t size, loff_t *pos)
> -{
> -	struct amdgpu_device *adev = file_inode(f)->i_private;
> -	ssize_t result, n;
> -	int r;
> -	uint64_t phys;
> -	void *ptr;
> -	struct iommu_domain *dom;
> +	// only accept page addresses
> +	if (*pos & 0xFFF)
> +		return -EINVAL;
>   
>   	dom = iommu_get_domain_for_dev(adev->dev);
> -	if (!dom)
> -		return -EFAULT;
> -
> -	result = 0;
> -	while (size) {
> -		// get physical address and map
> +	if (dom)
>   		phys = iommu_iova_to_phys(dom, *pos);
> +	else
> +		phys = *pos;
>   
> -		// copy upto one page
> -		if (size > PAGE_SIZE)
> -			n = PAGE_SIZE;
> -		else
> -			n = size;
> -
> -		// to end of the page
> -		if (((*pos & (PAGE_SIZE - 1)) + n) >= PAGE_SIZE)
> -			n = PAGE_SIZE - (*pos & (PAGE_SIZE - 1));
> -
> -		ptr = kmap(pfn_to_page(PFN_DOWN(phys)));
> -		if (!ptr)
> -			return -EFAULT;
> -
> -		r = copy_from_user(ptr, buf, n);
> -		kunmap(pfn_to_page(PFN_DOWN(phys)));
> -		if (r)
> -			return -EFAULT;
> -
> -		*pos += n;
> -		size -= n;
> -		result += n;
> -	}
> +	r = copy_to_user(buf, &phys, 8);
> +	if (r)
> +		return -EFAULT;
>   
> -	return result;
> +	return 8;
>   }
>   
>   static const struct file_operations amdgpu_ttm_iova_fops = {
>   	.owner = THIS_MODULE,
>   	.read = amdgpu_iova_to_phys_read,
> -	.write = amdgpu_iova_to_phys_write,
>   	.llseek = default_llseek
>   };
>