[PATCH 5/5] drm/amdgpu: replace iova debugfs file with iomem

[Tom St Denis]

Another thing that occurred to me is this will break write access to GPU 
bound memory.  Previously we relied on iova to translate the address and 
then /dev/mem or /dev/fmem to read/write it.  But since this is 
literally a read only method obviously there's no write support.

Tom


On 04/02/18 09:56 PM, He, Roger wrote:
> Patch1 & 2 & 4,   Reviewed-by: Roger He <Hongbo.He at amd.com>
> Patch 5:  Acked-by: Roger He <Hongbo.He at amd.com>
> 
> -----Original Message-----
> From: dri-devel [mailto:dri-devel-bounces at lists.freedesktop.org] On Behalf Of Christian K?nig
> Sent: Saturday, February 03, 2018 3:10 AM
> To: amd-gfx at lists.freedesktop.org; dri-devel at lists.freedesktop.org
> Subject: [PATCH 5/5] drm/amdgpu: replace iova debugfs file with iomem
> 
> This allows access to pages allocated through the driver with optional IOMMU mapping.
> 
> Signed-off-by: Christian König <christian.koenig at amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 57 ++++++++++++++++++++-------------
>   1 file changed, 35 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> index 648c449aaa79..795ceaeb82d5 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> @@ -1929,38 +1929,51 @@ static const struct file_operations amdgpu_ttm_gtt_fops = {
>   
>   #endif
>   
> -static ssize_t amdgpu_iova_to_phys_read(struct file *f, char __user *buf,
> -				   size_t size, loff_t *pos)
> +static ssize_t amdgpu_iomem_read(struct file *f, char __user *buf,
> +				 size_t size, loff_t *pos)
>   {
>   	struct amdgpu_device *adev = file_inode(f)->i_private;
> -	int r;
> -	uint64_t phys;
>   	struct iommu_domain *dom;
> +	ssize_t result = 0;
> +	int r;
>   
> -	// always return 8 bytes
> -	if (size != 8)
> -		return -EINVAL;
> +	dom = iommu_get_domain_for_dev(adev->dev);
>   
> -	// only accept page addresses
> -	if (*pos & 0xFFF)
> -		return -EINVAL;
> +	while (size) {
> +		phys_addr_t addr = *pos & PAGE_MASK;
> +		loff_t off = *pos & ~PAGE_MASK;
> +		size_t bytes = PAGE_SIZE - off;
> +		unsigned long pfn;
> +		struct page *p;
> +		void *ptr;
>   
> -	dom = iommu_get_domain_for_dev(adev->dev);
> -	if (dom)
> -		phys = iommu_iova_to_phys(dom, *pos);
> -	else
> -		phys = *pos;
> +		addr = dom ? iommu_iova_to_phys(dom, addr) : addr;
>   
> -	r = copy_to_user(buf, &phys, 8);
> -	if (r)
> -		return -EFAULT;
> +		pfn = addr >> PAGE_SHIFT;
> +		if (!pfn_valid(pfn))
> +			return -EPERM;
> +
> +		p = pfn_to_page(pfn);
> +		if (p->mapping != adev->mman.bdev.dev_mapping)
> +			return -EPERM;
> +
> +		ptr = kmap(p);
> +		r = copy_to_user(buf, ptr, bytes);
> +		kunmap(p);
> +		if (r)
> +			return -EFAULT;
>   
> -	return 8;
> +		size -= bytes;
> +		*pos += bytes;
> +		result += bytes;
> +	}
> +
> +	return result;
>   }
>   
> -static const struct file_operations amdgpu_ttm_iova_fops = {
> +static const struct file_operations amdgpu_ttm_iomem_fops = {
>   	.owner = THIS_MODULE,
> -	.read = amdgpu_iova_to_phys_read,
> +	.read = amdgpu_iomem_read,
>   	.llseek = default_llseek
>   };
>   
> @@ -1973,7 +1986,7 @@ static const struct {  #ifdef CONFIG_DRM_AMDGPU_GART_DEBUGFS
>   	{ "amdgpu_gtt", &amdgpu_ttm_gtt_fops, TTM_PL_TT },  #endif
> -	{ "amdgpu_iova", &amdgpu_ttm_iova_fops, TTM_PL_SYSTEM },
> +	{ "amdgpu_iomem", &amdgpu_ttm_iomem_fops, TTM_PL_SYSTEM },
>   };
>   
>   #endif
> --
> 2.14.1
> 
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