[PATCH v2 2/8] drm/ttm: Remap all page faults to per process dummy page.

[Andrey Grodzovsky <andrey.grodzovsky@xxxxxxx>]

On device removal reroute all CPU mappings to dummy page per drm_file
instance or imported GEM object.

Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@xxxxxxx>
---
 drivers/gpu/drm/ttm/ttm_bo_vm.c | 65 ++++++++++++++++++++++++++++++++++++-----
 1 file changed, 57 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
index 389128b..2f8bf5e 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
@@ -35,6 +35,8 @@
 #include <drm/ttm/ttm_bo_driver.h>
 #include <drm/ttm/ttm_placement.h>
 #include <drm/drm_vma_manager.h>
+#include <drm/drm_drv.h>
+#include <drm/drm_file.h>
 #include <linux/mm.h>
 #include <linux/pfn_t.h>
 #include <linux/rbtree.h>
@@ -328,19 +330,66 @@ vm_fault_t ttm_bo_vm_fault(struct vm_fault *vmf)
 	pgprot_t prot;
 	struct ttm_buffer_object *bo = vma->vm_private_data;
 	vm_fault_t ret;
+	int idx;
+	struct drm_device *ddev = bo->base.dev;
 
-	ret = ttm_bo_vm_reserve(bo, vmf);
-	if (ret)
-		return ret;
+	if (drm_dev_enter(ddev, &idx)) {
+		ret = ttm_bo_vm_reserve(bo, vmf);
+		if (ret)
+			goto exit;
+
+		prot = vma->vm_page_prot;
 
-	prot = vma->vm_page_prot;
-	ret = ttm_bo_vm_fault_reserved(vmf, prot, TTM_BO_VM_NUM_PREFAULT);
-	if (ret == VM_FAULT_RETRY && !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT))
+		ret = ttm_bo_vm_fault_reserved(vmf, prot, TTM_BO_VM_NUM_PREFAULT);
+		if (ret == VM_FAULT_RETRY && !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT))
+			goto exit;
+
+		dma_resv_unlock(bo->base.resv);
+
+exit:
+		drm_dev_exit(idx);
 		return ret;
+	} else {
 
-	dma_resv_unlock(bo->base.resv);
+		struct drm_file *file = NULL;
+		struct page *dummy_page = NULL;
+		int handle;
 
-	return ret;
+		/* We are faulting on imported BO from dma_buf */
+		if (bo->base.dma_buf && bo->base.import_attach) {
+			dummy_page = bo->base.dummy_page;
+		/* We are faulting on non imported BO, find drm_file owning the BO*/
+		} else {
+			struct drm_gem_object *gobj;
+
+			mutex_lock(&ddev->filelist_mutex);
+			list_for_each_entry(file, &ddev->filelist, lhead) {
+				spin_lock(&file->table_lock);
+				idr_for_each_entry(&file->object_idr, gobj, handle) {
+					if (gobj == &bo->base) {
+						dummy_page = file->dummy_page;
+						break;
+					}
+				}
+				spin_unlock(&file->table_lock);
+			}
+			mutex_unlock(&ddev->filelist_mutex);
+		}
+
+		if (dummy_page) {
+			/*
+			 * Let do_fault complete the PTE install e.t.c using vmf->page
+			 *
+			 * TODO - should i call free_page somewhere ?
+			 */
+			get_page(dummy_page);
+			vmf->page = dummy_page;
+			return 0;
+		} else {
+			return VM_FAULT_SIGSEGV;
+		}
+	}
 }
 EXPORT_SYMBOL(ttm_bo_vm_fault);
 
-- 
2.7.4

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