1 files changed, 374 insertions, 330 deletions

diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
index 3df9f16b041c..b47020fca199 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: GPL-2.0 OR MIT */
 /**************************************************************************
  *
  * Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA
@@ -30,436 +31,479 @@
 
 #define pr_fmt(fmt) "[TTM] " fmt
 
-#include <ttm/ttm_module.h>
-#include <ttm/ttm_bo_driver.h>
-#include <ttm/ttm_placement.h>
-#include <linux/mm.h>
-#include <linux/rbtree.h>
-#include <linux/module.h>
-#include <linux/uaccess.h>
+#include <linux/export.h>
 
-#define TTM_BO_VM_NUM_PREFAULT 16
+#include <drm/ttm/ttm_bo.h>
+#include <drm/ttm/ttm_placement.h>
+#include <drm/ttm/ttm_tt.h>
 
-static struct ttm_buffer_object *ttm_bo_vm_lookup_rb(struct ttm_bo_device *bdev,
-						     unsigned long page_start,
-						     unsigned long num_pages)
+#include <drm/drm_drv.h>
+#include <drm/drm_managed.h>
+
+static vm_fault_t ttm_bo_vm_fault_idle(struct ttm_buffer_object *bo,
+				struct vm_fault *vmf)
 {
-	struct rb_node *cur = bdev->addr_space_rb.rb_node;
-	unsigned long cur_offset;
-	struct ttm_buffer_object *bo;
-	struct ttm_buffer_object *best_bo = NULL;
-
-	while (likely(cur != NULL)) {
-		bo = rb_entry(cur, struct ttm_buffer_object, vm_rb);
-		cur_offset = bo->vm_node->start;
-		if (page_start >= cur_offset) {
-			cur = cur->rb_right;
-			best_bo = bo;
-			if (page_start == cur_offset)
-				break;
-		} else
-			cur = cur->rb_left;
-	}
+	long err = 0;
 
-	if (unlikely(best_bo == NULL))
-		return NULL;
+	/*
+	 * Quick non-stalling check for idle.
+	 */
+	if (dma_resv_test_signaled(bo->base.resv, DMA_RESV_USAGE_KERNEL))
+		return 0;
 
-	if (unlikely((best_bo->vm_node->start + best_bo->num_pages) <
-		     (page_start + num_pages)))
-		return NULL;
+	/*
+	 * If possible, avoid waiting for GPU with mmap_lock
+	 * held.  We only do this if the fault allows retry and this
+	 * is the first attempt.
+	 */
+	if (fault_flag_allow_retry_first(vmf->flags)) {
+		if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT)
+			return VM_FAULT_RETRY;
+
+		drm_gem_object_get(&bo->base);
+		mmap_read_unlock(vmf->vma->vm_mm);
+		(void)dma_resv_wait_timeout(bo->base.resv,
+					    DMA_RESV_USAGE_KERNEL, true,
+					    MAX_SCHEDULE_TIMEOUT);
+		dma_resv_unlock(bo->base.resv);
+		drm_gem_object_put(&bo->base);
+		return VM_FAULT_RETRY;
+	}
 
-	return best_bo;
+	/*
+	 * Ordinary wait.
+	 */
+	err = dma_resv_wait_timeout(bo->base.resv, DMA_RESV_USAGE_KERNEL, true,
+				    MAX_SCHEDULE_TIMEOUT);
+	if (unlikely(err < 0)) {
+		return (err != -ERESTARTSYS) ? VM_FAULT_SIGBUS :
+			VM_FAULT_NOPAGE;
+	}
+
+	return 0;
 }
 
-static int ttm_bo_vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
+static unsigned long ttm_bo_io_mem_pfn(struct ttm_buffer_object *bo,
+				       unsigned long page_offset)
 {
-	struct ttm_buffer_object *bo = (struct ttm_buffer_object *)
-	    vma->vm_private_data;
-	struct ttm_bo_device *bdev = bo->bdev;
-	unsigned long page_offset;
-	unsigned long page_last;
-	unsigned long pfn;
-	struct ttm_tt *ttm = NULL;
-	struct page *page;
-	int ret;
-	int i;
-	unsigned long address = (unsigned long)vmf->virtual_address;
-	int retval = VM_FAULT_NOPAGE;
-	struct ttm_mem_type_manager *man =
-		&bdev->man[bo->mem.mem_type];
+	struct ttm_device *bdev = bo->bdev;
 
+	if (bdev->funcs->io_mem_pfn)
+		return bdev->funcs->io_mem_pfn(bo, page_offset);
+
+	return (bo->resource->bus.offset >> PAGE_SHIFT) + page_offset;
+}
+
+/**
+ * ttm_bo_vm_reserve - Reserve a buffer object in a retryable vm callback
+ * @bo: The buffer object
+ * @vmf: The fault structure handed to the callback
+ *
+ * vm callbacks like fault() and *_mkwrite() allow for the mmap_lock to be dropped
+ * during long waits, and after the wait the callback will be restarted. This
+ * is to allow other threads using the same virtual memory space concurrent
+ * access to map(), unmap() completely unrelated buffer objects. TTM buffer
+ * object reservations sometimes wait for GPU and should therefore be
+ * considered long waits. This function reserves the buffer object interruptibly
+ * taking this into account. Starvation is avoided by the vm system not
+ * allowing too many repeated restarts.
+ * This function is intended to be used in customized fault() and _mkwrite()
+ * handlers.
+ *
+ * Return:
+ *    0 on success and the bo was reserved.
+ *    VM_FAULT_RETRY if blocking wait.
+ *    VM_FAULT_NOPAGE if blocking wait and retrying was not allowed.
+ */
+vm_fault_t ttm_bo_vm_reserve(struct ttm_buffer_object *bo,
+			     struct vm_fault *vmf)
+{
 	/*
 	 * Work around locking order reversal in fault / nopfn
-	 * between mmap_sem and bo_reserve: Perform a trylock operation
-	 * for reserve, and if it fails, retry the fault after scheduling.
+	 * between mmap_lock and bo_reserve: Perform a trylock operation
+	 * for reserve, and if it fails, retry the fault after waiting
+	 * for the buffer to become unreserved.
 	 */
+	if (unlikely(!dma_resv_trylock(bo->base.resv))) {
+		/*
+		 * If the fault allows retry and this is the first
+		 * fault attempt, we try to release the mmap_lock
+		 * before waiting
+		 */
+		if (fault_flag_allow_retry_first(vmf->flags)) {
+			if (!(vmf->flags & FAULT_FLAG_RETRY_NOWAIT)) {
+				drm_gem_object_get(&bo->base);
+				mmap_read_unlock(vmf->vma->vm_mm);
+				if (!dma_resv_lock_interruptible(bo->base.resv,
+								 NULL))
+					dma_resv_unlock(bo->base.resv);
+				drm_gem_object_put(&bo->base);
+			}
+
+			return VM_FAULT_RETRY;
+		}
 
-	ret = ttm_bo_reserve(bo, true, true, false, 0);
-	if (unlikely(ret != 0)) {
-		if (ret == -EBUSY)
-			set_need_resched();
-		return VM_FAULT_NOPAGE;
+		if (dma_resv_lock_interruptible(bo->base.resv, NULL))
+			return VM_FAULT_NOPAGE;
 	}
 
-	if (bdev->driver->fault_reserve_notify) {
-		ret = bdev->driver->fault_reserve_notify(bo);
-		switch (ret) {
-		case 0:
-			break;
-		case -EBUSY:
-			set_need_resched();
-		case -ERESTARTSYS:
-			retval = VM_FAULT_NOPAGE;
-			goto out_unlock;
-		default:
-			retval = VM_FAULT_SIGBUS;
-			goto out_unlock;
+	/*
+	 * Refuse to fault imported pages. This should be handled
+	 * (if at all) by redirecting mmap to the exporter.
+	 */
+	if (bo->ttm && (bo->ttm->page_flags & TTM_TT_FLAG_EXTERNAL)) {
+		if (!(bo->ttm->page_flags & TTM_TT_FLAG_EXTERNAL_MAPPABLE)) {
+			dma_resv_unlock(bo->base.resv);
+			return VM_FAULT_SIGBUS;
 		}
 	}
 
+	return 0;
+}
+EXPORT_SYMBOL(ttm_bo_vm_reserve);
+
+/**
+ * ttm_bo_vm_fault_reserved - TTM fault helper
+ * @vmf: The struct vm_fault given as argument to the fault callback
+ * @prot: The page protection to be used for this memory area.
+ * @num_prefault: Maximum number of prefault pages. The caller may want to
+ * specify this based on madvice settings and the size of the GPU object
+ * backed by the memory.
+ *
+ * This function inserts one or more page table entries pointing to the
+ * memory backing the buffer object, and then returns a return code
+ * instructing the caller to retry the page access.
+ *
+ * Return:
+ *   VM_FAULT_NOPAGE on success or pending signal
+ *   VM_FAULT_SIGBUS on unspecified error
+ *   VM_FAULT_OOM on out-of-memory
+ *   VM_FAULT_RETRY if retryable wait
+ */
+vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf,
+				    pgprot_t prot,
+				    pgoff_t num_prefault)
+{
+	struct vm_area_struct *vma = vmf->vma;
+	struct ttm_buffer_object *bo = vma->vm_private_data;
+	struct ttm_device *bdev = bo->bdev;
+	unsigned long page_offset;
+	unsigned long page_last;
+	unsigned long pfn;
+	struct ttm_tt *ttm = NULL;
+	struct page *page;
+	int err;
+	pgoff_t i;
+	vm_fault_t ret = VM_FAULT_NOPAGE;
+	unsigned long address = vmf->address;
+
 	/*
 	 * Wait for buffer data in transit, due to a pipelined
 	 * move.
 	 */
+	ret = ttm_bo_vm_fault_idle(bo, vmf);
+	if (unlikely(ret != 0))
+		return ret;
 
-	spin_lock(&bdev->fence_lock);
-	if (test_bit(TTM_BO_PRIV_FLAG_MOVING, &bo->priv_flags)) {
-		ret = ttm_bo_wait(bo, false, true, false);
-		spin_unlock(&bdev->fence_lock);
-		if (unlikely(ret != 0)) {
-			retval = (ret != -ERESTARTSYS) ?
-			    VM_FAULT_SIGBUS : VM_FAULT_NOPAGE;
-			goto out_unlock;
-		}
-	} else
-		spin_unlock(&bdev->fence_lock);
-
-	ret = ttm_mem_io_lock(man, true);
-	if (unlikely(ret != 0)) {
-		retval = VM_FAULT_NOPAGE;
-		goto out_unlock;
-	}
-	ret = ttm_mem_io_reserve_vm(bo);
-	if (unlikely(ret != 0)) {
-		retval = VM_FAULT_SIGBUS;
-		goto out_io_unlock;
-	}
+	err = ttm_mem_io_reserve(bdev, bo->resource);
+	if (unlikely(err != 0))
+		return VM_FAULT_SIGBUS;
 
 	page_offset = ((address - vma->vm_start) >> PAGE_SHIFT) +
-	    bo->vm_node->start - vma->vm_pgoff;
-	page_last = vma_pages(vma) +
-	    bo->vm_node->start - vma->vm_pgoff;
+		vma->vm_pgoff - drm_vma_node_start(&bo->base.vma_node);
+	page_last = vma_pages(vma) + vma->vm_pgoff -
+		drm_vma_node_start(&bo->base.vma_node);
 
-	if (unlikely(page_offset >= bo->num_pages)) {
-		retval = VM_FAULT_SIGBUS;
-		goto out_io_unlock;
-	}
+	if (unlikely(page_offset >= PFN_UP(bo->base.size)))
+		return VM_FAULT_SIGBUS;
+
+	prot = ttm_io_prot(bo, bo->resource, prot);
+	if (!bo->resource->bus.is_iomem) {
+		struct ttm_operation_ctx ctx = {
+			.interruptible = true,
+			.no_wait_gpu = false,
+		};
 
-	/*
-	 * Strictly, we're not allowed to modify vma->vm_page_prot here,
-	 * since the mmap_sem is only held in read mode. However, we
-	 * modify only the caching bits of vma->vm_page_prot and
-	 * consider those bits protected by
-	 * the bo->mutex, as we should be the only writers.
-	 * There shouldn't really be any readers of these bits except
-	 * within vm_insert_mixed()? fork?
-	 *
-	 * TODO: Add a list of vmas to the bo, and change the
-	 * vma->vm_page_prot when the object changes caching policy, with
-	 * the correct locks held.
-	 */
-	if (bo->mem.bus.is_iomem) {
-		vma->vm_page_prot = ttm_io_prot(bo->mem.placement,
-						vma->vm_page_prot);
-	} else {
 		ttm = bo->ttm;
-		vma->vm_page_prot = (bo->mem.placement & TTM_PL_FLAG_CACHED) ?
-		    vm_get_page_prot(vma->vm_flags) :
-		    ttm_io_prot(bo->mem.placement, vma->vm_page_prot);
-
-		/* Allocate all page at once, most common usage */
-		if (ttm->bdev->driver->ttm_tt_populate(ttm)) {
-			retval = VM_FAULT_OOM;
-			goto out_io_unlock;
+		err = ttm_bo_populate(bo, &ctx);
+		if (err) {
+			if (err == -EINTR || err == -ERESTARTSYS ||
+			    err == -EAGAIN)
+				return VM_FAULT_NOPAGE;
+
+			pr_debug("TTM fault hit %pe.\n", ERR_PTR(err));
+			return VM_FAULT_SIGBUS;
 		}
+	} else {
+		/* Iomem should not be marked encrypted */
+		prot = pgprot_decrypted(prot);
 	}
 
 	/*
 	 * Speculatively prefault a number of pages. Only error on
 	 * first page.
 	 */
-	for (i = 0; i < TTM_BO_VM_NUM_PREFAULT; ++i) {
-		if (bo->mem.bus.is_iomem)
-			pfn = ((bo->mem.bus.base + bo->mem.bus.offset) >> PAGE_SHIFT) + page_offset;
-		else {
+	for (i = 0; i < num_prefault; ++i) {
+		if (bo->resource->bus.is_iomem) {
+			pfn = ttm_bo_io_mem_pfn(bo, page_offset);
+		} else {
 			page = ttm->pages[page_offset];
 			if (unlikely(!page && i == 0)) {
-				retval = VM_FAULT_OOM;
-				goto out_io_unlock;
+				return VM_FAULT_OOM;
 			} else if (unlikely(!page)) {
 				break;
 			}
 			pfn = page_to_pfn(page);
 		}
 
-		ret = vm_insert_mixed(vma, address, pfn);
 		/*
-		 * Somebody beat us to this PTE or prefaulting to
-		 * an already populated PTE, or prefaulting error.
+		 * Note that the value of @prot at this point may differ from
+		 * the value of @vma->vm_page_prot in the caching- and
+		 * encryption bits. This is because the exact location of the
+		 * data may not be known at mmap() time and may also change
+		 * at arbitrary times while the data is mmap'ed.
+		 * See vmf_insert_pfn_prot() for a discussion.
 		 */
+		ret = vmf_insert_pfn_prot(vma, address, pfn, prot);
 
-		if (unlikely((ret == -EBUSY) || (ret != 0 && i > 0)))
-			break;
-		else if (unlikely(ret != 0)) {
-			retval =
-			    (ret == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS;
-			goto out_io_unlock;
+		/* Never error on prefaulted PTEs */
+		if (unlikely((ret & VM_FAULT_ERROR))) {
+			if (i == 0)
+				return VM_FAULT_NOPAGE;
+			else
+				break;
 		}
 
 		address += PAGE_SIZE;
 		if (unlikely(++page_offset >= page_last))
 			break;
 	}
-out_io_unlock:
-	ttm_mem_io_unlock(man);
-out_unlock:
-	ttm_bo_unreserve(bo);
-	return retval;
+	return ret;
 }
+EXPORT_SYMBOL(ttm_bo_vm_fault_reserved);
 
-static void ttm_bo_vm_open(struct vm_area_struct *vma)
+static void ttm_bo_release_dummy_page(struct drm_device *dev, void *res)
 {
-	struct ttm_buffer_object *bo =
-	    (struct ttm_buffer_object *)vma->vm_private_data;
+	struct page *dummy_page = (struct page *)res;
 
-	(void)ttm_bo_reference(bo);
+	__free_page(dummy_page);
 }
 
-static void ttm_bo_vm_close(struct vm_area_struct *vma)
+vm_fault_t ttm_bo_vm_dummy_page(struct vm_fault *vmf, pgprot_t prot)
 {
-	struct ttm_buffer_object *bo = (struct ttm_buffer_object *)vma->vm_private_data;
+	struct vm_area_struct *vma = vmf->vma;
+	struct ttm_buffer_object *bo = vma->vm_private_data;
+	struct drm_device *ddev = bo->base.dev;
+	vm_fault_t ret = VM_FAULT_NOPAGE;
+	unsigned long address;
+	unsigned long pfn;
+	struct page *page;
 
-	ttm_bo_unref(&bo);
-	vma->vm_private_data = NULL;
-}
+	/* Allocate new dummy page to map all the VA range in this VMA to it*/
+	page = alloc_page(GFP_KERNEL | __GFP_ZERO);
+	if (!page)
+		return VM_FAULT_OOM;
 
-static const struct vm_operations_struct ttm_bo_vm_ops = {
-	.fault = ttm_bo_vm_fault,
-	.open = ttm_bo_vm_open,
-	.close = ttm_bo_vm_close
-};
+	/* Set the page to be freed using drmm release action */
+	if (drmm_add_action_or_reset(ddev, ttm_bo_release_dummy_page, page))
+		return VM_FAULT_OOM;
 
-int ttm_bo_mmap(struct file *filp, struct vm_area_struct *vma,
-		struct ttm_bo_device *bdev)
-{
-	struct ttm_bo_driver *driver;
-	struct ttm_buffer_object *bo;
-	int ret;
+	pfn = page_to_pfn(page);
 
-	read_lock(&bdev->vm_lock);
-	bo = ttm_bo_vm_lookup_rb(bdev, vma->vm_pgoff,
-				 vma_pages(vma));
-	if (likely(bo != NULL) && !kref_get_unless_zero(&bo->kref))
-		bo = NULL;
-	read_unlock(&bdev->vm_lock);
+	/* Prefault the entire VMA range right away to avoid further faults */
+	for (address = vma->vm_start; address < vma->vm_end;
+	     address += PAGE_SIZE)
+		ret = vmf_insert_pfn_prot(vma, address, pfn, prot);
 
-	if (unlikely(bo == NULL)) {
-		pr_err("Could not find buffer object to map\n");
-		return -EINVAL;
-	}
+	return ret;
+}
+EXPORT_SYMBOL(ttm_bo_vm_dummy_page);
+
+vm_fault_t ttm_bo_vm_fault(struct vm_fault *vmf)
+{
+	struct vm_area_struct *vma = vmf->vma;
+	pgprot_t prot;
+	struct ttm_buffer_object *bo = vma->vm_private_data;
+	struct drm_device *ddev = bo->base.dev;
+	vm_fault_t ret;
+	int idx;
+
+	ret = ttm_bo_vm_reserve(bo, vmf);
+	if (ret)
+		return ret;
 
-	driver = bo->bdev->driver;
-	if (unlikely(!driver->verify_access)) {
-		ret = -EPERM;
-		goto out_unref;
+	prot = vma->vm_page_prot;
+	if (drm_dev_enter(ddev, &idx)) {
+		ret = ttm_bo_vm_fault_reserved(vmf, prot, TTM_BO_VM_NUM_PREFAULT);
+		drm_dev_exit(idx);
+	} else {
+		ret = ttm_bo_vm_dummy_page(vmf, prot);
 	}
-	ret = driver->verify_access(bo, filp);
-	if (unlikely(ret != 0))
-		goto out_unref;
+	if (ret == VM_FAULT_RETRY && !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT))
+		return ret;
 
-	vma->vm_ops = &ttm_bo_vm_ops;
+	dma_resv_unlock(bo->base.resv);
 
-	/*
-	 * Note: We're transferring the bo reference to
-	 * vma->vm_private_data here.
-	 */
-
-	vma->vm_private_data = bo;
-	vma->vm_flags |= VM_IO | VM_MIXEDMAP | VM_DONTEXPAND | VM_DONTDUMP;
-	return 0;
-out_unref:
-	ttm_bo_unref(&bo);
 	return ret;
 }
-EXPORT_SYMBOL(ttm_bo_mmap);
+EXPORT_SYMBOL(ttm_bo_vm_fault);
 
-int ttm_fbdev_mmap(struct vm_area_struct *vma, struct ttm_buffer_object *bo)
+void ttm_bo_vm_open(struct vm_area_struct *vma)
 {
-	if (vma->vm_pgoff != 0)
-		return -EACCES;
+	struct ttm_buffer_object *bo = vma->vm_private_data;
 
-	vma->vm_ops = &ttm_bo_vm_ops;
-	vma->vm_private_data = ttm_bo_reference(bo);
-	vma->vm_flags |= VM_IO | VM_MIXEDMAP | VM_DONTEXPAND;
-	return 0;
+	WARN_ON(bo->bdev->dev_mapping != vma->vm_file->f_mapping);
+
+	drm_gem_object_get(&bo->base);
 }
-EXPORT_SYMBOL(ttm_fbdev_mmap);
+EXPORT_SYMBOL(ttm_bo_vm_open);
 
+void ttm_bo_vm_close(struct vm_area_struct *vma)
+{
+	struct ttm_buffer_object *bo = vma->vm_private_data;
 
-ssize_t ttm_bo_io(struct ttm_bo_device *bdev, struct file *filp,
-		  const char __user *wbuf, char __user *rbuf, size_t count,
-		  loff_t *f_pos, bool write)
+	drm_gem_object_put(&bo->base);
+	vma->vm_private_data = NULL;
+}
+EXPORT_SYMBOL(ttm_bo_vm_close);
+
+static int ttm_bo_vm_access_kmap(struct ttm_buffer_object *bo,
+				 unsigned long offset,
+				 uint8_t *buf, int len, int write)
 {
-	struct ttm_buffer_object *bo;
-	struct ttm_bo_driver *driver;
-	struct ttm_bo_kmap_obj map;
-	unsigned long dev_offset = (*f_pos >> PAGE_SHIFT);
-	unsigned long kmap_offset;
-	unsigned long kmap_end;
-	unsigned long kmap_num;
-	size_t io_size;
-	unsigned int page_offset;
-	char *virtual;
+	unsigned long page = offset >> PAGE_SHIFT;
+	unsigned long bytes_left = len;
 	int ret;
-	bool no_wait = false;
-	bool dummy;
-
-	read_lock(&bdev->vm_lock);
-	bo = ttm_bo_vm_lookup_rb(bdev, dev_offset, 1);
-	if (likely(bo != NULL))
-		ttm_bo_reference(bo);
-	read_unlock(&bdev->vm_lock);
-
-	if (unlikely(bo == NULL))
-		return -EFAULT;
-
-	driver = bo->bdev->driver;
-	if (unlikely(!driver->verify_access)) {
-		ret = -EPERM;
-		goto out_unref;
-	}
-
-	ret = driver->verify_access(bo, filp);
-	if (unlikely(ret != 0))
-		goto out_unref;
 
-	kmap_offset = dev_offset - bo->vm_node->start;
-	if (unlikely(kmap_offset >= bo->num_pages)) {
-		ret = -EFBIG;
-		goto out_unref;
-	}
+	/* Copy a page at a time, that way no extra virtual address
+	 * mapping is needed
+	 */
+	offset -= page << PAGE_SHIFT;
+	do {
+		unsigned long bytes = min(bytes_left, PAGE_SIZE - offset);
+		struct ttm_bo_kmap_obj map;
+		void *ptr;
+		bool is_iomem;
+
+		ret = ttm_bo_kmap(bo, page, 1, &map);
+		if (ret)
+			return ret;
+
+		ptr = (uint8_t *)ttm_kmap_obj_virtual(&map, &is_iomem) + offset;
+		WARN_ON_ONCE(is_iomem);
+		if (write)
+			memcpy(ptr, buf, bytes);
+		else
+			memcpy(buf, ptr, bytes);
+		ttm_bo_kunmap(&map);
+
+		page++;
+		buf += bytes;
+		bytes_left -= bytes;
+		offset = 0;
+	} while (bytes_left);
+
+	return len;
+}
 
-	page_offset = *f_pos & ~PAGE_MASK;
-	io_size = bo->num_pages - kmap_offset;
-	io_size = (io_size << PAGE_SHIFT) - page_offset;
-	if (count < io_size)
-		io_size = count;
+/**
+ * ttm_bo_access - Helper to access a buffer object
+ *
+ * @bo: ttm buffer object
+ * @offset: access offset into buffer object
+ * @buf: pointer to caller memory to read into or write from
+ * @len: length of access
+ * @write: write access
+ *
+ * Utility function to access a buffer object. Useful when buffer object cannot
+ * be easily mapped (non-contiguous, non-visible, etc...). Should not directly
+ * be exported to user space via a peak / poke interface.
+ *
+ * Returns:
+ * @len if successful, negative error code on failure.
+ */
+int ttm_bo_access(struct ttm_buffer_object *bo, unsigned long offset,
+		  void *buf, int len, int write)
+{
+	int ret;
 
-	kmap_end = (*f_pos + count - 1) >> PAGE_SHIFT;
-	kmap_num = kmap_end - kmap_offset + 1;
+	if (len < 1 || (offset + len) > bo->base.size)
+		return -EIO;
 
-	ret = ttm_bo_reserve(bo, true, no_wait, false, 0);
+	ret = ttm_bo_reserve(bo, true, false, NULL);
+	if (ret)
+		return ret;
 
-	switch (ret) {
-	case 0:
+	switch (bo->resource->mem_type) {
+	case TTM_PL_SYSTEM:
+		fallthrough;
+	case TTM_PL_TT:
+		ret = ttm_bo_vm_access_kmap(bo, offset, buf, len, write);
 		break;
-	case -EBUSY:
-		ret = -EAGAIN;
-		goto out_unref;
 	default:
-		goto out_unref;
-	}
-
-	ret = ttm_bo_kmap(bo, kmap_offset, kmap_num, &map);
-	if (unlikely(ret != 0)) {
-		ttm_bo_unreserve(bo);
-		goto out_unref;
+		if (bo->bdev->funcs->access_memory)
+			ret = bo->bdev->funcs->access_memory
+				(bo, offset, buf, len, write);
+		else
+			ret = -EIO;
 	}
 
-	virtual = ttm_kmap_obj_virtual(&map, &dummy);
-	virtual += page_offset;
-
-	if (write)
-		ret = copy_from_user(virtual, wbuf, io_size);
-	else
-		ret = copy_to_user(rbuf, virtual, io_size);
-
-	ttm_bo_kunmap(&map);
 	ttm_bo_unreserve(bo);
-	ttm_bo_unref(&bo);
-
-	if (unlikely(ret != 0))
-		return -EFBIG;
 
-	*f_pos += io_size;
-
-	return io_size;
-out_unref:
-	ttm_bo_unref(&bo);
 	return ret;
 }
+EXPORT_SYMBOL(ttm_bo_access);
 
-ssize_t ttm_bo_fbdev_io(struct ttm_buffer_object *bo, const char __user *wbuf,
-			char __user *rbuf, size_t count, loff_t *f_pos,
-			bool write)
+int ttm_bo_vm_access(struct vm_area_struct *vma, unsigned long addr,
+		     void *buf, int len, int write)
 {
-	struct ttm_bo_kmap_obj map;
-	unsigned long kmap_offset;
-	unsigned long kmap_end;
-	unsigned long kmap_num;
-	size_t io_size;
-	unsigned int page_offset;
-	char *virtual;
-	int ret;
-	bool no_wait = false;
-	bool dummy;
-
-	kmap_offset = (*f_pos >> PAGE_SHIFT);
-	if (unlikely(kmap_offset >= bo->num_pages))
-		return -EFBIG;
-
-	page_offset = *f_pos & ~PAGE_MASK;
-	io_size = bo->num_pages - kmap_offset;
-	io_size = (io_size << PAGE_SHIFT) - page_offset;
-	if (count < io_size)
-		io_size = count;
-
-	kmap_end = (*f_pos + count - 1) >> PAGE_SHIFT;
-	kmap_num = kmap_end - kmap_offset + 1;
-
-	ret = ttm_bo_reserve(bo, true, no_wait, false, 0);
+	struct ttm_buffer_object *bo = vma->vm_private_data;
+	unsigned long offset = (addr) - vma->vm_start +
+		((vma->vm_pgoff - drm_vma_node_start(&bo->base.vma_node))
+		 << PAGE_SHIFT);
 
-	switch (ret) {
-	case 0:
-		break;
-	case -EBUSY:
-		return -EAGAIN;
-	default:
-		return ret;
-	}
+	return ttm_bo_access(bo, offset, buf, len, write);
+}
+EXPORT_SYMBOL(ttm_bo_vm_access);
 
-	ret = ttm_bo_kmap(bo, kmap_offset, kmap_num, &map);
-	if (unlikely(ret != 0)) {
-		ttm_bo_unreserve(bo);
-		return ret;
-	}
+static const struct vm_operations_struct ttm_bo_vm_ops = {
+	.fault = ttm_bo_vm_fault,
+	.open = ttm_bo_vm_open,
+	.close = ttm_bo_vm_close,
+	.access = ttm_bo_vm_access,
+};
 
-	virtual = ttm_kmap_obj_virtual(&map, &dummy);
-	virtual += page_offset;
+/**
+ * ttm_bo_mmap_obj - mmap memory backed by a ttm buffer object.
+ *
+ * @vma:       vma as input from the fbdev mmap method.
+ * @bo:        The bo backing the address space.
+ *
+ * Maps a buffer object.
+ */
+int ttm_bo_mmap_obj(struct vm_area_struct *vma, struct ttm_buffer_object *bo)
+{
+	/* Enforce no COW since would have really strange behavior with it. */
+	if (is_cow_mapping(vma->vm_flags))
+		return -EINVAL;
 
-	if (write)
-		ret = copy_from_user(virtual, wbuf, io_size);
-	else
-		ret = copy_to_user(rbuf, virtual, io_size);
+	drm_gem_object_get(&bo->base);
 
-	ttm_bo_kunmap(&map);
-	ttm_bo_unreserve(bo);
-	ttm_bo_unref(&bo);
+	/*
+	 * Drivers may want to override the vm_ops field. Otherwise we
+	 * use TTM's default callbacks.
+	 */
+	if (!vma->vm_ops)
+		vma->vm_ops = &ttm_bo_vm_ops;
 
-	if (unlikely(ret != 0))
-		return ret;
+	/*
+	 * Note: We're transferring the bo reference to
+	 * vma->vm_private_data here.
+	 */
 
-	*f_pos += io_size;
+	vma->vm_private_data = bo;
 
-	return io_size;
+	vm_flags_set(vma, VM_PFNMAP | VM_IO | VM_DONTEXPAND | VM_DONTDUMP);
+	return 0;
 }
+EXPORT_SYMBOL(ttm_bo_mmap_obj);