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

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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@xxxxxxx>
Patch 5:  Acked-by: Roger He <Hongbo.He@xxxxxxx>

-----Original Message-----
From: dri-devel [mailto:dri-devel-bounces@xxxxxxxxxxxxxxxxxxxxx] On Behalf Of Christian K?nig
Sent: Saturday, February 03, 2018 3:10 AM
To: amd-gfx@xxxxxxxxxxxxxxxxxxxxx; dri-devel@xxxxxxxxxxxxxxxxxxxxx
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@xxxxxxx>
---
  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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