--- /dev/null
+/*
+ * Copyright 2018 Red Hat Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ */
+#include "nouveau_dmem.h"
+#include "nouveau_drv.h"
+#include "nouveau_chan.h"
+#include "nouveau_dma.h"
+#include "nouveau_mem.h"
+#include "nouveau_bo.h"
+
+#include <nvif/class.h>
+#include <nvif/object.h>
+#include <nvif/if500b.h>
+#include <nvif/if900b.h>
+
+#include <linux/sched/mm.h>
+#include <linux/hmm.h>
+
+/*
+ * FIXME: this is ugly right now we are using TTM to allocate vram and we pin
+ * it in vram while in use. We likely want to overhaul memory management for
+ * nouveau to be more page like (not necessarily with system page size but a
+ * bigger page size) at lowest level and have some shim layer on top that would
+ * provide the same functionality as TTM.
+ */
+#define DMEM_CHUNK_SIZE (2UL << 20)
+#define DMEM_CHUNK_NPAGES (DMEM_CHUNK_SIZE >> PAGE_SHIFT)
+
+struct nouveau_migrate;
+
+typedef int (*nouveau_migrate_copy_t)(struct nouveau_drm *drm, u64 npages,
+                                     u64 dst_addr, u64 src_addr);
+
+struct nouveau_dmem_chunk {
+       struct list_head list;
+       struct nouveau_bo *bo;
+       struct nouveau_drm *drm;
+       unsigned long pfn_first;
+       unsigned long callocated;
+       unsigned long bitmap[BITS_TO_LONGS(DMEM_CHUNK_NPAGES)];
+       struct nvif_vma vma;
+       spinlock_t lock;
+};
+
+struct nouveau_dmem_migrate {
+       nouveau_migrate_copy_t copy_func;
+       struct nouveau_channel *chan;
+};
+
+struct nouveau_dmem {
+       struct hmm_devmem *devmem;
+       struct nouveau_dmem_migrate migrate;
+       struct list_head chunk_free;
+       struct list_head chunk_full;
+       struct list_head chunk_empty;
+       struct mutex mutex;
+};
+
+struct nouveau_migrate_hmem {
+       struct scatterlist *sg;
+       struct nouveau_mem mem;
+       unsigned long npages;
+       struct nvif_vma vma;
+};
+
+struct nouveau_dmem_fault {
+       struct nouveau_drm *drm;
+       struct nouveau_fence *fence;
+       struct nouveau_migrate_hmem hmem;
+};
+
+struct nouveau_migrate {
+       struct vm_area_struct *vma;
+       struct nouveau_drm *drm;
+       struct nouveau_fence *fence;
+       unsigned long npages;
+       struct nouveau_migrate_hmem hmem;
+};
+
+static void
+nouveau_migrate_hmem_fini(struct nouveau_drm *drm,
+                         struct nouveau_migrate_hmem *hmem)
+{
+       struct nvif_vmm *vmm = &drm->client.vmm.vmm;
+
+       nouveau_mem_fini(&hmem->mem);
+       nvif_vmm_put(vmm, &hmem->vma);
+
+       if (hmem->sg) {
+               dma_unmap_sg_attrs(drm->dev->dev, hmem->sg,
+                                  hmem->npages, DMA_BIDIRECTIONAL,
+                                  DMA_ATTR_SKIP_CPU_SYNC);
+               kfree(hmem->sg);
+               hmem->sg = NULL;
+       }
+}
+
+static int
+nouveau_migrate_hmem_init(struct nouveau_drm *drm,
+                         struct nouveau_migrate_hmem *hmem,
+                         unsigned long npages,
+                         const unsigned long *pfns)
+{
+       struct nvif_vmm *vmm = &drm->client.vmm.vmm;
+       unsigned long i;
+       int ret;
+
+       hmem->sg = kzalloc(npages * sizeof(*hmem->sg), GFP_KERNEL);
+       if (hmem->sg == NULL)
+               return -ENOMEM;
+
+       for (i = 0, hmem->npages = 0; hmem->npages < npages; ++i) {
+               struct page *page;
+
+               if (!pfns[i] || pfns[i] == MIGRATE_PFN_ERROR)
+                       continue;
+
+               page = migrate_pfn_to_page(pfns[i]);
+               if (page == NULL) {
+                       ret = -EINVAL;
+                       goto error;
+               }
+
+               sg_set_page(&hmem->sg[hmem->npages], page, PAGE_SIZE, 0);
+               hmem->npages++;
+       }
+       sg_mark_end(&hmem->sg[hmem->npages - 1]);
+
+       i = dma_map_sg_attrs(drm->dev->dev, hmem->sg, hmem->npages,
+                            DMA_BIDIRECTIONAL, DMA_ATTR_SKIP_CPU_SYNC);
+       if (i != hmem->npages) {
+               ret = -ENOMEM;
+               goto error;
+       }
+
+       ret = nouveau_mem_sgl(&hmem->mem, &drm->client,
+                             hmem->npages, hmem->sg);
+       if (ret)
+               goto error;
+
+       ret = nvif_vmm_get(vmm, LAZY, false, hmem->mem.mem.page,
+                          0, hmem->mem.mem.size, &hmem->vma);
+       if (ret)
+               goto error;
+
+       ret = nouveau_mem_map(&hmem->mem, vmm, &hmem->vma);
+       if (ret)
+               goto error;
+
+       return 0;
+
+error:
+       nouveau_migrate_hmem_fini(drm, hmem);
+       return ret;
+}
+
+
+static void
+nouveau_dmem_free(struct hmm_devmem *devmem, struct page *page)
+{
+       struct nouveau_dmem_chunk *chunk;
+       struct nouveau_drm *drm;
+       unsigned long idx;
+
+       chunk = (void *)hmm_devmem_page_get_drvdata(page);
+       idx = page_to_pfn(page) - chunk->pfn_first;
+       drm = chunk->drm;
+
+       /*
+        * FIXME:
+        *
+        * This is really a bad example, we need to overhaul nouveau memory
+        * management to be more page focus and allow lighter locking scheme
+        * to be use in the process.
+        */
+       spin_lock(&chunk->lock);
+       clear_bit(idx, chunk->bitmap);
+       WARN_ON(!chunk->callocated);
+       chunk->callocated--;
+       /*
+        * FIXME when chunk->callocated reach 0 we should add the chunk to
+        * a reclaim list so that it can be freed in case of memory pressure.
+        */
+       spin_unlock(&chunk->lock);
+}
+
+static void
+nouveau_dmem_fault_alloc_and_copy(struct vm_area_struct *vma,
+                                 const unsigned long *src_pfns,
+                                 unsigned long *dst_pfns,
+                                 unsigned long start,
+                                 unsigned long end,
+                                 void *private)
+{
+       struct nouveau_dmem_fault *fault = private;
+       struct nouveau_drm *drm = fault->drm;
+       unsigned long addr, i, c, npages = 0;
+       nouveau_migrate_copy_t copy;
+       int ret;
+
+
+       /* First allocate new memory */
+       for (addr = start, i = 0; addr < end; addr += PAGE_SIZE, i++) {
+               struct page *dpage, *spage;
+
+               dst_pfns[i] = 0;
+               spage = migrate_pfn_to_page(src_pfns[i]);
+               if (!spage || !(src_pfns[i] & MIGRATE_PFN_MIGRATE))
+                       continue;
+
+               dpage = hmm_vma_alloc_locked_page(vma, addr);
+               if (!dpage) {
+                       dst_pfns[i] = MIGRATE_PFN_ERROR;
+                       continue;
+               }
+
+               dst_pfns[i] = migrate_pfn(page_to_pfn(dpage)) |
+                             MIGRATE_PFN_LOCKED;
+               npages++;
+       }
+
+       /* Create scatter list FIXME: get rid of scatter list */
+       ret = nouveau_migrate_hmem_init(drm, &fault->hmem, npages, dst_pfns);
+       if (ret)
+               goto error;
+
+       /* Copy things over */
+       copy = drm->dmem->migrate.copy_func;
+       for (addr = start, i = c = 0; addr < end; addr += PAGE_SIZE, i++) {
+               struct nouveau_dmem_chunk *chunk;
+               struct page *spage, *dpage;
+               u64 src_addr, dst_addr;
+
+               dpage = migrate_pfn_to_page(dst_pfns[i]);
+               if (!dpage || dst_pfns[i] == MIGRATE_PFN_ERROR)
+                       continue;
+
+               dst_addr = fault->hmem.vma.addr + (c << PAGE_SHIFT);
+               c++;
+
+               spage = migrate_pfn_to_page(src_pfns[i]);
+               if (!spage || !(src_pfns[i] & MIGRATE_PFN_MIGRATE)) {
+                       dst_pfns[i] = MIGRATE_PFN_ERROR;
+                       __free_page(dpage);
+                       continue;
+               }
+
+               chunk = (void *)hmm_devmem_page_get_drvdata(spage);
+               src_addr = page_to_pfn(spage) - chunk->pfn_first;
+               src_addr = (src_addr << PAGE_SHIFT) + chunk->vma.addr;
+
+               ret = copy(drm, 1, dst_addr, src_addr);
+               if (ret) {
+                       dst_pfns[i] = MIGRATE_PFN_ERROR;
+                       __free_page(dpage);
+                       continue;
+               }
+       }
+
+       nouveau_fence_new(drm->dmem->migrate.chan, false, &fault->fence);
+
+       return;
+
+error:
+       for (addr = start, i = 0; addr < end; addr += PAGE_SIZE, ++i) {
+               struct page *page;
+
+               if (!dst_pfns[i] || dst_pfns[i] == MIGRATE_PFN_ERROR)
+                       continue;
+
+               page = migrate_pfn_to_page(dst_pfns[i]);
+               dst_pfns[i] = MIGRATE_PFN_ERROR;
+               if (page == NULL)
+                       continue;
+
+               __free_page(page);
+       }
+}
+
+void nouveau_dmem_fault_finalize_and_map(struct vm_area_struct *vma,
+                                        const unsigned long *src_pfns,
+                                        const unsigned long *dst_pfns,
+                                        unsigned long start,
+                                        unsigned long end,
+                                        void *private)
+{
+       struct nouveau_dmem_fault *fault = private;
+       struct nouveau_drm *drm = fault->drm;
+
+       if (fault->fence) {
+               nouveau_fence_wait(fault->fence, true, false);
+               nouveau_fence_unref(&fault->fence);
+       } else {
+               /*
+                * FIXME wait for channel to be IDLE before calling finalizing
+                * the hmem object below (nouveau_migrate_hmem_fini()).
+                */
+       }
+       nouveau_migrate_hmem_fini(drm, &fault->hmem);
+}
+
+static const struct migrate_vma_ops nouveau_dmem_fault_migrate_ops = {
+       .alloc_and_copy         = nouveau_dmem_fault_alloc_and_copy,
+       .finalize_and_map       = nouveau_dmem_fault_finalize_and_map,
+};
+
+static int
+nouveau_dmem_fault(struct hmm_devmem *devmem,
+                  struct vm_area_struct *vma,
+                  unsigned long addr,
+                  const struct page *page,
+                  unsigned int flags,
+                  pmd_t *pmdp)
+{
+       struct drm_device *drm_dev = dev_get_drvdata(devmem->device);
+       unsigned long src[1] = {0}, dst[1] = {0};
+       struct nouveau_dmem_fault fault = {0};
+       int ret;
+
+
+
+       /*
+        * FIXME what we really want is to find some heuristic to migrate more
+        * than just one page on CPU fault. When such fault happens it is very
+        * likely that more surrounding page will CPU fault too.
+        */
+       fault.drm = nouveau_drm(drm_dev);
+       ret = migrate_vma(&nouveau_dmem_fault_migrate_ops, vma, addr,
+                         addr + PAGE_SIZE, src, dst, &fault);
+       if (ret)
+               return VM_FAULT_SIGBUS;
+
+       if (dst[0] == MIGRATE_PFN_ERROR)
+               return VM_FAULT_SIGBUS;
+
+       return 0;
+}
+
+static const struct hmm_devmem_ops
+nouveau_dmem_devmem_ops = {
+       .free = nouveau_dmem_free,
+       .fault = nouveau_dmem_fault,
+};
+
+static int
+nouveau_dmem_chunk_alloc(struct nouveau_drm *drm)
+{
+       struct nvif_vmm *vmm = &drm->client.vmm.vmm;
+       struct nouveau_dmem_chunk *chunk;
+       int ret;
+
+       if (drm->dmem == NULL)
+               return -EINVAL;
+
+       mutex_lock(&drm->dmem->mutex);
+       chunk = list_first_entry_or_null(&drm->dmem->chunk_empty,
+                                        struct nouveau_dmem_chunk,
+                                        list);
+       if (chunk == NULL) {
+               mutex_unlock(&drm->dmem->mutex);
+               return -ENOMEM;
+       }
+
+       list_del(&chunk->list);
+       mutex_unlock(&drm->dmem->mutex);
+
+       ret = nvif_vmm_get(vmm, LAZY, false, 12, 0,
+                          DMEM_CHUNK_SIZE, &chunk->vma);
+       if (ret)
+               goto out;
+
+       ret = nouveau_bo_new(&drm->client, DMEM_CHUNK_SIZE, 0,
+                            TTM_PL_FLAG_VRAM, 0, 0, NULL, NULL,
+                            &chunk->bo);
+       if (ret)
+               goto out;
+
+       ret = nouveau_bo_pin(chunk->bo, TTM_PL_FLAG_VRAM, false);
+       if (ret) {
+               nouveau_bo_ref(NULL, &chunk->bo);
+               goto out;
+       }
+
+       ret = nouveau_mem_map(nouveau_mem(&chunk->bo->bo.mem), vmm, &chunk->vma);
+       if (ret) {
+               nouveau_bo_unpin(chunk->bo);
+               nouveau_bo_ref(NULL, &chunk->bo);
+               goto out;
+       }
+
+       bitmap_zero(chunk->bitmap, DMEM_CHUNK_NPAGES);
+       spin_lock_init(&chunk->lock);
+
+out:
+       mutex_lock(&drm->dmem->mutex);
+       if (chunk->bo)
+               list_add(&chunk->list, &drm->dmem->chunk_empty);
+       else
+               list_add_tail(&chunk->list, &drm->dmem->chunk_empty);
+       mutex_unlock(&drm->dmem->mutex);
+
+       return ret;
+}
+
+static struct nouveau_dmem_chunk *
+nouveau_dmem_chunk_first_free_locked(struct nouveau_drm *drm)
+{
+       struct nouveau_dmem_chunk *chunk;
+
+       chunk = list_first_entry_or_null(&drm->dmem->chunk_free,
+                                        struct nouveau_dmem_chunk,
+                                        list);
+       if (chunk)
+               return chunk;
+
+       chunk = list_first_entry_or_null(&drm->dmem->chunk_empty,
+                                        struct nouveau_dmem_chunk,
+                                        list);
+       if (chunk->bo)
+               return chunk;
+
+       return NULL;
+}
+
+static int
+nouveau_dmem_pages_alloc(struct nouveau_drm *drm,
+                        unsigned long npages,
+                        unsigned long *pages)
+{
+       struct nouveau_dmem_chunk *chunk;
+       unsigned long c;
+       int ret;
+
+       memset(pages, 0xff, npages * sizeof(*pages));
+
+       mutex_lock(&drm->dmem->mutex);
+       for (c = 0; c < npages;) {
+               unsigned long i;
+
+               chunk = nouveau_dmem_chunk_first_free_locked(drm);
+               if (chunk == NULL) {
+                       mutex_unlock(&drm->dmem->mutex);
+                       ret = nouveau_dmem_chunk_alloc(drm);
+                       if (ret) {
+                               if (c)
+                                       break;
+                               return ret;
+                       }
+                       continue;
+               }
+
+               spin_lock(&chunk->lock);
+               i = find_first_zero_bit(chunk->bitmap, DMEM_CHUNK_NPAGES);
+               while (i < DMEM_CHUNK_NPAGES && c < npages) {
+                       pages[c] = chunk->pfn_first + i;
+                       set_bit(i, chunk->bitmap);
+                       chunk->callocated++;
+                       c++;
+
+                       i = find_next_zero_bit(chunk->bitmap,
+                                       DMEM_CHUNK_NPAGES, i);
+               }
+               spin_unlock(&chunk->lock);
+       }
+       mutex_unlock(&drm->dmem->mutex);
+
+       return 0;
+}
+
+static struct page *
+nouveau_dmem_page_alloc_locked(struct nouveau_drm *drm)
+{
+       unsigned long pfns[1];
+       struct page *page;
+       int ret;
+
+       /* FIXME stop all the miss-match API ... */
+       ret = nouveau_dmem_pages_alloc(drm, 1, pfns);
+       if (ret)
+               return NULL;
+
+       page = pfn_to_page(pfns[0]);
+       get_page(page);
+       lock_page(page);
+       return page;
+}
+
+static void
+nouveau_dmem_page_free_locked(struct nouveau_drm *drm, struct page *page)
+{
+       unlock_page(page);
+       put_page(page);
+}
+
+void
+nouveau_dmem_resume(struct nouveau_drm *drm)
+{
+       struct nouveau_dmem_chunk *chunk;
+       int ret;
+
+       if (drm->dmem == NULL)
+               return;
+
+       mutex_lock(&drm->dmem->mutex);
+       list_for_each_entry (chunk, &drm->dmem->chunk_free, list) {
+               ret = nouveau_bo_pin(chunk->bo, TTM_PL_FLAG_VRAM, false);
+               /* FIXME handle pin failure */
+               WARN_ON(ret);
+       }
+       list_for_each_entry (chunk, &drm->dmem->chunk_full, list) {
+               ret = nouveau_bo_pin(chunk->bo, TTM_PL_FLAG_VRAM, false);
+               /* FIXME handle pin failure */
+               WARN_ON(ret);
+       }
+       list_for_each_entry (chunk, &drm->dmem->chunk_empty, list) {
+               ret = nouveau_bo_pin(chunk->bo, TTM_PL_FLAG_VRAM, false);
+               /* FIXME handle pin failure */
+               WARN_ON(ret);
+       }
+       mutex_unlock(&drm->dmem->mutex);
+}
+
+void
+nouveau_dmem_suspend(struct nouveau_drm *drm)
+{
+       struct nouveau_dmem_chunk *chunk;
+
+       if (drm->dmem == NULL)
+               return;
+
+       mutex_lock(&drm->dmem->mutex);
+       list_for_each_entry (chunk, &drm->dmem->chunk_free, list) {
+               nouveau_bo_unpin(chunk->bo);
+       }
+       list_for_each_entry (chunk, &drm->dmem->chunk_full, list) {
+               nouveau_bo_unpin(chunk->bo);
+       }
+       list_for_each_entry (chunk, &drm->dmem->chunk_empty, list) {
+               nouveau_bo_unpin(chunk->bo);
+       }
+       mutex_unlock(&drm->dmem->mutex);
+}
+
+void
+nouveau_dmem_fini(struct nouveau_drm *drm)
+{
+       struct nvif_vmm *vmm = &drm->client.vmm.vmm;
+       struct nouveau_dmem_chunk *chunk, *tmp;
+
+       if (drm->dmem == NULL)
+               return;
+
+       mutex_lock(&drm->dmem->mutex);
+
+       WARN_ON(!list_empty(&drm->dmem->chunk_free));
+       WARN_ON(!list_empty(&drm->dmem->chunk_full));
+
+       list_for_each_entry_safe (chunk, tmp, &drm->dmem->chunk_empty, list) {
+               if (chunk->bo) {
+                       nouveau_bo_unpin(chunk->bo);
+                       nouveau_bo_ref(NULL, &chunk->bo);
+               }
+               nvif_vmm_put(vmm, &chunk->vma);
+               list_del(&chunk->list);
+               kfree(chunk);
+       }
+
+       mutex_unlock(&drm->dmem->mutex);
+}
+
+static int
+nvc0b5_migrate_copy(struct nouveau_drm *drm, u64 npages,
+                   u64 dst_addr, u64 src_addr)
+{
+       struct nouveau_channel *chan = drm->dmem->migrate.chan;
+       int ret;
+
+       ret = RING_SPACE(chan, 10);
+       if (ret)
+               return ret;
+
+       BEGIN_NVC0(chan, NvSubCopy, 0x0400, 8);
+       OUT_RING  (chan, upper_32_bits(src_addr));
+       OUT_RING  (chan, lower_32_bits(src_addr));
+       OUT_RING  (chan, upper_32_bits(dst_addr));
+       OUT_RING  (chan, lower_32_bits(dst_addr));
+       OUT_RING  (chan, PAGE_SIZE);
+       OUT_RING  (chan, PAGE_SIZE);
+       OUT_RING  (chan, PAGE_SIZE);
+       OUT_RING  (chan, npages);
+       BEGIN_IMC0(chan, NvSubCopy, 0x0300, 0x0386);
+       return 0;
+}
+
+static int
+nouveau_dmem_migrate_init(struct nouveau_drm *drm)
+{
+       switch (drm->ttm.copy.oclass) {
+       case PASCAL_DMA_COPY_A:
+       case PASCAL_DMA_COPY_B:
+       case  VOLTA_DMA_COPY_A:
+       case TURING_DMA_COPY_A:
+               drm->dmem->migrate.copy_func = nvc0b5_migrate_copy;
+               drm->dmem->migrate.chan = drm->ttm.chan;
+               return 0;
+       default:
+               break;
+       }
+       return -ENODEV;
+}
+
+void
+nouveau_dmem_init(struct nouveau_drm *drm)
+{
+       struct device *device = drm->dev->dev;
+       unsigned long i, size;
+       int ret;
+
+       /* This only make sense on PASCAL or newer */
+       if (drm->client.device.info.family < NV_DEVICE_INFO_V0_PASCAL)
+               return;
+
+       if (!(drm->dmem = kzalloc(sizeof(*drm->dmem), GFP_KERNEL)))
+               return;
+
+       mutex_init(&drm->dmem->mutex);
+       INIT_LIST_HEAD(&drm->dmem->chunk_free);
+       INIT_LIST_HEAD(&drm->dmem->chunk_full);
+       INIT_LIST_HEAD(&drm->dmem->chunk_empty);
+
+       size = ALIGN(drm->client.device.info.ram_user, DMEM_CHUNK_SIZE);
+
+       /* Initialize migration dma helpers before registering memory */
+       ret = nouveau_dmem_migrate_init(drm);
+       if (ret) {
+               kfree(drm->dmem);
+               drm->dmem = NULL;
+               return;
+       }
+
+       /*
+        * FIXME we need some kind of policy to decide how much VRAM we
+        * want to register with HMM. For now just register everything
+        * and latter if we want to do thing like over commit then we
+        * could revisit this.
+        */
+       drm->dmem->devmem = hmm_devmem_add(&nouveau_dmem_devmem_ops,
+                                          device, size);
+       if (drm->dmem->devmem == NULL) {
+               kfree(drm->dmem);
+               drm->dmem = NULL;
+               return;
+       }
+
+       for (i = 0; i < (size / DMEM_CHUNK_SIZE); ++i) {
+               struct nouveau_dmem_chunk *chunk;
+               struct page *page;
+               unsigned long j;
+
+               chunk = kzalloc(sizeof(*chunk), GFP_KERNEL);
+               if (chunk == NULL) {
+                       nouveau_dmem_fini(drm);
+                       return;
+               }
+
+               chunk->drm = drm;
+               chunk->pfn_first = drm->dmem->devmem->pfn_first;
+               chunk->pfn_first += (i * DMEM_CHUNK_NPAGES);
+               list_add_tail(&chunk->list, &drm->dmem->chunk_empty);
+
+               page = pfn_to_page(chunk->pfn_first);
+               for (j = 0; j < DMEM_CHUNK_NPAGES; ++j, ++page) {
+                       hmm_devmem_page_set_drvdata(page, (long)chunk);
+               }
+       }
+
+       NV_INFO(drm, "DMEM: registered %ldMB of device memory\n", size >> 20);
+}
+
+static void
+nouveau_dmem_migrate_alloc_and_copy(struct vm_area_struct *vma,
+                                   const unsigned long *src_pfns,
+                                   unsigned long *dst_pfns,
+                                   unsigned long start,
+                                   unsigned long end,
+                                   void *private)
+{
+       struct nouveau_migrate *migrate = private;
+       struct nouveau_drm *drm = migrate->drm;
+       unsigned long addr, i, c, npages = 0;
+       nouveau_migrate_copy_t copy;
+       int ret;
+
+       /* First allocate new memory */
+       for (addr = start, i = 0; addr < end; addr += PAGE_SIZE, i++) {
+               struct page *dpage, *spage;
+
+               dst_pfns[i] = 0;
+               spage = migrate_pfn_to_page(src_pfns[i]);
+               if (!spage || !(src_pfns[i] & MIGRATE_PFN_MIGRATE))
+                       continue;
+
+               dpage = nouveau_dmem_page_alloc_locked(drm);
+               if (!dpage)
+                       continue;
+
+               dst_pfns[i] = migrate_pfn(page_to_pfn(dpage)) |
+                             MIGRATE_PFN_LOCKED |
+                             MIGRATE_PFN_DEVICE;
+               npages++;
+       }
+
+       if (!npages)
+               return;
+
+       /* Create scatter list FIXME: get rid of scatter list */
+       ret = nouveau_migrate_hmem_init(drm, &migrate->hmem, npages, src_pfns);
+       if (ret)
+               goto error;
+
+       /* Copy things over */
+       copy = drm->dmem->migrate.copy_func;
+       for (addr = start, i = c = 0; addr < end; addr += PAGE_SIZE, i++) {
+               struct nouveau_dmem_chunk *chunk;
+               struct page *spage, *dpage;
+               u64 src_addr, dst_addr;
+
+               dpage = migrate_pfn_to_page(dst_pfns[i]);
+               if (!dpage || dst_pfns[i] == MIGRATE_PFN_ERROR)
+                       continue;
+
+               chunk = (void *)hmm_devmem_page_get_drvdata(dpage);
+               dst_addr = page_to_pfn(dpage) - chunk->pfn_first;
+               dst_addr = (dst_addr << PAGE_SHIFT) + chunk->vma.addr;
+
+               spage = migrate_pfn_to_page(src_pfns[i]);
+               if (!spage || !(src_pfns[i] & MIGRATE_PFN_MIGRATE)) {
+                       nouveau_dmem_page_free_locked(drm, dpage);
+                       dst_pfns[i] = 0;
+                       continue;
+               }
+
+               src_addr = migrate->hmem.vma.addr + (c << PAGE_SHIFT);
+               c++;
+
+               ret = copy(drm, 1, dst_addr, src_addr);
+               if (ret) {
+                       nouveau_dmem_page_free_locked(drm, dpage);
+                       dst_pfns[i] = 0;
+                       continue;
+               }
+       }
+
+       nouveau_fence_new(drm->dmem->migrate.chan, false, &migrate->fence);
+
+       return;
+
+error:
+       for (addr = start, i = 0; addr < end; addr += PAGE_SIZE, ++i) {
+               struct page *page;
+
+               if (!dst_pfns[i] || dst_pfns[i] == MIGRATE_PFN_ERROR)
+                       continue;
+
+               page = migrate_pfn_to_page(dst_pfns[i]);
+               dst_pfns[i] = MIGRATE_PFN_ERROR;
+               if (page == NULL)
+                       continue;
+
+               __free_page(page);
+       }
+}
+
+void nouveau_dmem_migrate_finalize_and_map(struct vm_area_struct *vma,
+                                          const unsigned long *src_pfns,
+                                          const unsigned long *dst_pfns,
+                                          unsigned long start,
+                                          unsigned long end,
+                                          void *private)
+{
+       struct nouveau_migrate *migrate = private;
+       struct nouveau_drm *drm = migrate->drm;
+
+       if (migrate->fence) {
+               nouveau_fence_wait(migrate->fence, true, false);
+               nouveau_fence_unref(&migrate->fence);
+       } else {
+               /*
+                * FIXME wait for channel to be IDLE before finalizing
+                * the hmem object below (nouveau_migrate_hmem_fini()) ?
+                */
+       }
+       nouveau_migrate_hmem_fini(drm, &migrate->hmem);
+
+       /*
+        * FIXME optimization: update GPU page table to point to newly
+        * migrated memory.
+        */
+}
+
+static const struct migrate_vma_ops nouveau_dmem_migrate_ops = {
+       .alloc_and_copy         = nouveau_dmem_migrate_alloc_and_copy,
+       .finalize_and_map       = nouveau_dmem_migrate_finalize_and_map,
+};
+
+int
+nouveau_dmem_migrate_vma(struct nouveau_drm *drm,
+                        struct vm_area_struct *vma,
+                        unsigned long start,
+                        unsigned long end)
+{
+       unsigned long *src_pfns, *dst_pfns, npages;
+       struct nouveau_migrate migrate = {0};
+       unsigned long i, c, max;
+       int ret = 0;
+
+       npages = (end - start) >> PAGE_SHIFT;
+       max = min(SG_MAX_SINGLE_ALLOC, npages);
+       src_pfns = kzalloc(sizeof(long) * max, GFP_KERNEL);
+       if (src_pfns == NULL)
+               return -ENOMEM;
+       dst_pfns = kzalloc(sizeof(long) * max, GFP_KERNEL);
+       if (dst_pfns == NULL) {
+               kfree(src_pfns);
+               return -ENOMEM;
+       }
+
+       migrate.drm = drm;
+       migrate.vma = vma;
+       migrate.npages = npages;
+       for (i = 0; i < npages; i += c) {
+               unsigned long next;
+
+               c = min(SG_MAX_SINGLE_ALLOC, npages);
+               next = start + (c << PAGE_SHIFT);
+               ret = migrate_vma(&nouveau_dmem_migrate_ops, vma, start,
+                                 next, src_pfns, dst_pfns, &migrate);
+               if (ret)
+                       goto out;
+               start = next;
+       }
+
+out:
+       kfree(dst_pfns);
+       kfree(src_pfns);
+       return ret;
+}
+
+static inline bool
+nouveau_dmem_page(struct nouveau_drm *drm, struct page *page)
+{
+       if (!is_device_private_page(page))
+               return false;
+
+       if (drm->dmem->devmem != page->pgmap->data)
+               return false;
+
+       return true;
+}
+
+void
+nouveau_dmem_convert_pfn(struct nouveau_drm *drm,
+                        struct hmm_range *range)
+{
+       unsigned long i, npages;
+
+       npages = (range->end - range->start) >> PAGE_SHIFT;
+       for (i = 0; i < npages; ++i) {
+               struct nouveau_dmem_chunk *chunk;
+               struct page *page;
+               uint64_t addr;
+
+               page = hmm_pfn_to_page(range, range->pfns[i]);
+               if (page == NULL)
+                       continue;
+
+               if (!(range->pfns[i] & range->flags[HMM_PFN_DEVICE_PRIVATE])) {
+                       continue;
+               }
+
+               if (!nouveau_dmem_page(drm, page)) {
+                       WARN(1, "Some unknown device memory !\n");
+                       range->pfns[i] = 0;
+                       continue;
+               }
+
+               chunk = (void *)hmm_devmem_page_get_drvdata(page);
+               addr = page_to_pfn(page) - chunk->pfn_first;
+               addr = (addr + chunk->bo->bo.mem.start) << PAGE_SHIFT;
+
+               range->pfns[i] &= ((1UL << range->pfn_shift) - 1);
+               range->pfns[i] |= (addr >> PAGE_SHIFT) << range->pfn_shift;
+       }
+}