drm/amdgpu: GPU vs CPU page size fixes in amdgpu_vm_bo_split_mapping

start / last / max_entries are numbers of GPU pages, pfn / count are
numbers of CPU pages. Convert between them accordingly.

Fixes badness on systems with > 4K page size.

Cc: stable@vger.kernel.org
Bugzilla: https://bugs.freedesktop.org/106258Reported-by: Matt Corallo <freedesktop@bluematt.me>
Tested-by: foxbat@ruin.net
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c

@@ -1463,7 +1463,9 @@ static int amdgpu_vm_bo_split_mapping(struct amdgpu_device *adev,
 			uint64_t count;
 
 			max_entries = min(max_entries, 16ull * 1024ull);
-			for (count = 1; count < max_entries; ++count) {
+			for (count = 1;
+			     count < max_entries / (PAGE_SIZE / AMDGPU_GPU_PAGE_SIZE);
+			     ++count) {
 				uint64_t idx = pfn + count;
 
 				if (pages_addr[idx] !=
@@ -1476,7 +1478,7 @@ static int amdgpu_vm_bo_split_mapping(struct amdgpu_device *adev,
 				dma_addr = pages_addr;
 			} else {
 				addr = pages_addr[pfn];
-				max_entries = count;
+				max_entries = count * (PAGE_SIZE / AMDGPU_GPU_PAGE_SIZE);
 			}
 
 		} else if (flags & AMDGPU_PTE_VALID) {
@@ -1491,7 +1493,7 @@ static int amdgpu_vm_bo_split_mapping(struct amdgpu_device *adev,
 		if (r)
 			return r;
 
-		pfn += last - start + 1;
+		pfn += (last - start + 1) / (PAGE_SIZE / AMDGPU_GPU_PAGE_SIZE);
 		if (nodes && nodes->size == pfn) {
 			pfn = 0;
 			++nodes;