// SPDX-License-Identifier: GPL-2.0 OR MIT
/*
 * Copyright 2020-2021 Advanced Micro Devices, 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 <linux/types.h>
#include <linux/hmm.h>
#include <linux/dma-direction.h>
#include <linux/dma-mapping.h>
#include "amdgpu_sync.h"
#include "amdgpu_object.h"
#include "amdgpu_vm.h"
#include "amdgpu_mn.h"
#include "amdgpu_res_cursor.h"
#include "kfd_priv.h"
#include "kfd_svm.h"
#include "kfd_migrate.h"

static uint64_t
svm_migrate_direct_mapping_addr(struct amdgpu_device *adev, uint64_t addr)
{
        return addr + amdgpu_ttm_domain_start(adev, TTM_PL_VRAM);
}

static int
svm_migrate_gart_map(struct amdgpu_ring *ring, uint64_t npages,
                     dma_addr_t *addr, uint64_t *gart_addr, uint64_t flags)
{
        struct amdgpu_device *adev = ring->adev;
        struct amdgpu_job *job;
        unsigned int num_dw, num_bytes;
        struct dma_fence *fence;
        uint64_t src_addr, dst_addr;
        uint64_t pte_flags;
        void *cpu_addr;
        int r;

        /* use gart window 0 */
        *gart_addr = adev->gmc.gart_start;

        num_dw = ALIGN(adev->mman.buffer_funcs->copy_num_dw, 8);
        num_bytes = npages * 8;

        r = amdgpu_job_alloc_with_ib(adev, num_dw * 4 + num_bytes,
                                     AMDGPU_IB_POOL_DELAYED, &job);
        if (r)
                return r;

        src_addr = num_dw * 4;
        src_addr += job->ibs[0].gpu_addr;

        dst_addr = amdgpu_bo_gpu_offset(adev->gart.bo);
        amdgpu_emit_copy_buffer(adev, &job->ibs[0], src_addr,
                                dst_addr, num_bytes, false);

        amdgpu_ring_pad_ib(ring, &job->ibs[0]);
        WARN_ON(job->ibs[0].length_dw > num_dw);

        pte_flags = AMDGPU_PTE_VALID | AMDGPU_PTE_READABLE;
        pte_flags |= AMDGPU_PTE_SYSTEM | AMDGPU_PTE_SNOOPED;
        if (!(flags & KFD_IOCTL_SVM_FLAG_GPU_RO))
                pte_flags |= AMDGPU_PTE_WRITEABLE;
        pte_flags |= adev->gart.gart_pte_flags;

        cpu_addr = &job->ibs[0].ptr[num_dw];

        r = amdgpu_gart_map(adev, 0, npages, addr, pte_flags, cpu_addr);
        if (r)
                goto error_free;

        r = amdgpu_job_submit(job, &adev->mman.entity,
                              AMDGPU_FENCE_OWNER_UNDEFINED, &fence);
        if (r)
                goto error_free;

        dma_fence_put(fence);

        return r;

error_free:
        amdgpu_job_free(job);
        return r;
}

/**
 * svm_migrate_copy_memory_gart - sdma copy data between ram and vram
 *
 * @adev: amdgpu device the sdma ring running
 * @src: source page address array
 * @dst: destination page address array
 * @npages: number of pages to copy
 * @direction: enum MIGRATION_COPY_DIR
 * @mfence: output, sdma fence to signal after sdma is done
 *
 * ram address uses GART table continuous entries mapping to ram pages,
 * vram address uses direct mapping of vram pages, which must have npages
 * number of continuous pages.
 * GART update and sdma uses same buf copy function ring, sdma is splited to
 * multiple GTT_MAX_PAGES transfer, all sdma operations are serialized, wait for
 * the last sdma finish fence which is returned to check copy memory is done.
 *
 * Context: Process context, takes and releases gtt_window_lock
 *
 * Return:
 * 0 - OK, otherwise error code
 */

static int
svm_migrate_copy_memory_gart(struct amdgpu_device *adev, dma_addr_t *sys,
                             uint64_t *vram, uint64_t npages,
                             enum MIGRATION_COPY_DIR direction,
                             struct dma_fence **mfence)
{
        const uint64_t GTT_MAX_PAGES = AMDGPU_GTT_MAX_TRANSFER_SIZE;
        struct amdgpu_ring *ring = adev->mman.buffer_funcs_ring;
        uint64_t gart_s, gart_d;
        struct dma_fence *next;
        uint64_t size;
        int r;

        mutex_lock(&adev->mman.gtt_window_lock);

        while (npages) {
                size = min(GTT_MAX_PAGES, npages);

                if (direction == FROM_VRAM_TO_RAM) {
                        gart_s = svm_migrate_direct_mapping_addr(adev, *vram);
                        r = svm_migrate_gart_map(ring, size, sys, &gart_d, 0);

                } else if (direction == FROM_RAM_TO_VRAM) {
                        r = svm_migrate_gart_map(ring, size, sys, &gart_s,
                                                 KFD_IOCTL_SVM_FLAG_GPU_RO);
                        gart_d = svm_migrate_direct_mapping_addr(adev, *vram);
                }
                if (r) {
                        pr_debug("failed %d to create gart mapping\n", r);
                        goto out_unlock;
                }

                r = amdgpu_copy_buffer(ring, gart_s, gart_d, size * PAGE_SIZE,
                                       NULL, &next, false, true, false);
                if (r) {
                        pr_debug("failed %d to copy memory\n", r);
                        goto out_unlock;
                }

                dma_fence_put(*mfence);
                *mfence = next;
                npages -= size;
                if (npages) {
                        sys += size;
                        vram += size;
                }
        }

out_unlock:
        mutex_unlock(&adev->mman.gtt_window_lock);

        return r;
}

/**
 * svm_migrate_copy_done - wait for memory copy sdma is done
 *
 * @adev: amdgpu device the sdma memory copy is executing on
 * @mfence: migrate fence
 *
 * Wait for dma fence is signaled, if the copy ssplit into multiple sdma
 * operations, this is the last sdma operation fence.
 *
 * Context: called after svm_migrate_copy_memory
 *
 * Return:
 * 0            - success
 * otherwise    - error code from dma fence signal
 */
static int
svm_migrate_copy_done(struct amdgpu_device *adev, struct dma_fence *mfence)
{
        int r = 0;

        if (mfence) {
                r = dma_fence_wait(mfence, false);
                dma_fence_put(mfence);
                pr_debug("sdma copy memory fence done\n");
        }

        return r;
}

unsigned long
svm_migrate_addr_to_pfn(struct amdgpu_device *adev, unsigned long addr)
{
        return (addr + adev->kfd.dev->pgmap.range.start) >> PAGE_SHIFT;
}

static void
svm_migrate_get_vram_page(struct svm_range *prange, unsigned long pfn)
{
        struct page *page;

        page = pfn_to_page(pfn);
        svm_range_bo_ref(prange->svm_bo);
        page->zone_device_data = prange->svm_bo;
        get_page(page);
        lock_page(page);
}

static void
svm_migrate_put_vram_page(struct amdgpu_device *adev, unsigned long addr)
{
        struct page *page;

        page = pfn_to_page(svm_migrate_addr_to_pfn(adev, addr));
        unlock_page(page);
        put_page(page);
}

static unsigned long
svm_migrate_addr(struct amdgpu_device *adev, struct page *page)
{
        unsigned long addr;

        addr = page_to_pfn(page) << PAGE_SHIFT;
        return (addr - adev->kfd.dev->pgmap.range.start);
}

static struct page *
svm_migrate_get_sys_page(struct vm_area_struct *vma, unsigned long addr)
{
        struct page *page;

        page = alloc_page_vma(GFP_HIGHUSER, vma, addr);
        if (page)
                lock_page(page);

        return page;
}

static void svm_migrate_put_sys_page(unsigned long addr)
{
        struct page *page;

        page = pfn_to_page(addr >> PAGE_SHIFT);
        unlock_page(page);
        put_page(page);
}

static int
svm_migrate_copy_to_vram(struct amdgpu_device *adev, struct svm_range *prange,
                         struct migrate_vma *migrate, struct dma_fence **mfence,
                         dma_addr_t *scratch)
{
        uint64_t npages = migrate->cpages;
        struct device *dev = adev->dev;
        struct amdgpu_res_cursor cursor;
        dma_addr_t *src;
        uint64_t *dst;
        uint64_t i, j;
        int r;

        pr_debug("svms 0x%p [0x%lx 0x%lx]\n", prange->svms, prange->start,
                 prange->last);

        src = scratch;
        dst = (uint64_t *)(scratch + npages);

        r = svm_range_vram_node_new(adev, prange, true);
        if (r) {
                pr_debug("failed %d get 0x%llx pages from vram\n", r, npages);
                goto out;
        }

        amdgpu_res_first(prange->ttm_res, prange->offset << PAGE_SHIFT,
                         npages << PAGE_SHIFT, &cursor);
        for (i = j = 0; i < npages; i++) {
                struct page *spage;

                spage = migrate_pfn_to_page(migrate->src[i]);
                if (spage && !is_zone_device_page(spage)) {
                        dst[i] = cursor.start + (j << PAGE_SHIFT);
                        migrate->dst[i] = svm_migrate_addr_to_pfn(adev, dst[i]);
                        svm_migrate_get_vram_page(prange, migrate->dst[i]);
                        migrate->dst[i] = migrate_pfn(migrate->dst[i]);
                        migrate->dst[i] |= MIGRATE_PFN_LOCKED;
                        src[i] = dma_map_page(dev, spage, 0, PAGE_SIZE,
                                              DMA_TO_DEVICE);
                        r = dma_mapping_error(dev, src[i]);
                        if (r) {
                                pr_debug("failed %d dma_map_page\n", r);
                                goto out_free_vram_pages;
                        }
                } else {
                        if (j) {
                                r = svm_migrate_copy_memory_gart(
                                                adev, src + i - j,
                                                dst + i - j, j,
                                                FROM_RAM_TO_VRAM,
                                                mfence);
                                if (r)
                                        goto out_free_vram_pages;
                                amdgpu_res_next(&cursor, j << PAGE_SHIFT);
                                j = 0;
                        } else {
                                amdgpu_res_next(&cursor, PAGE_SIZE);
                        }
                        continue;
                }

                pr_debug("dma mapping src to 0x%llx, page_to_pfn 0x%lx\n",
                         src[i] >> PAGE_SHIFT, page_to_pfn(spage));

                if (j >= (cursor.size >> PAGE_SHIFT) - 1 && i < npages - 1) {
                        r = svm_migrate_copy_memory_gart(adev, src + i - j,
                                                         dst + i - j, j + 1,
                                                         FROM_RAM_TO_VRAM,
                                                         mfence);
                        if (r)
                                goto out_free_vram_pages;
                        amdgpu_res_next(&cursor, (j + 1) * PAGE_SIZE);
                        j= 0;
                } else {
                        j++;
                }
        }

        r = svm_migrate_copy_memory_gart(adev, src + i - j, dst + i - j, j,
                                         FROM_RAM_TO_VRAM, mfence);

out_free_vram_pages:
        if (r) {
                pr_debug("failed %d to copy memory to vram\n", r);
                while (i--) {
                        svm_migrate_put_vram_page(adev, dst[i]);
                        migrate->dst[i] = 0;
                }
        }

#ifdef DEBUG_FORCE_MIXED_DOMAINS
        for (i = 0, j = 0; i < npages; i += 4, j++) {
                if (j & 1)
                        continue;
                svm_migrate_put_vram_page(adev, dst[i]);
                migrate->dst[i] = 0;
                svm_migrate_put_vram_page(adev, dst[i + 1]);
                migrate->dst[i + 1] = 0;
                svm_migrate_put_vram_page(adev, dst[i + 2]);
                migrate->dst[i + 2] = 0;
                svm_migrate_put_vram_page(adev, dst[i + 3]);
                migrate->dst[i + 3] = 0;
        }
#endif
out:
        return r;
}

static int
svm_migrate_vma_to_vram(struct amdgpu_device *adev, struct svm_range *prange,
                        struct vm_area_struct *vma, uint64_t start,
                        uint64_t end)
{
        uint64_t npages = (end - start) >> PAGE_SHIFT;
        struct kfd_process_device *pdd;
        struct dma_fence *mfence = NULL;
        struct migrate_vma migrate;
        dma_addr_t *scratch;
        size_t size;
        void *buf;
        int r = -ENOMEM;

        memset(&migrate, 0, sizeof(migrate));
        migrate.vma = vma;
        migrate.start = start;
        migrate.end = end;
        migrate.flags = MIGRATE_VMA_SELECT_SYSTEM;
        migrate.pgmap_owner = SVM_ADEV_PGMAP_OWNER(adev);

        size = 2 * sizeof(*migrate.src) + sizeof(uint64_t) + sizeof(dma_addr_t);
        size *= npages;
        buf = kvmalloc(size, GFP_KERNEL | __GFP_ZERO);
        if (!buf)
                goto out;

        migrate.src = buf;
        migrate.dst = migrate.src + npages;
        scratch = (dma_addr_t *)(migrate.dst + npages);

        r = migrate_vma_setup(&migrate);
        if (r) {
                pr_debug("failed %d prepare migrate svms 0x%p [0x%lx 0x%lx]\n",
                         r, prange->svms, prange->start, prange->last);
                goto out_free;
        }
        if (migrate.cpages != npages) {
                pr_debug("Partial migration. 0x%lx/0x%llx pages can be migrated\n",
                         migrate.cpages,
                         npages);
        }

        if (migrate.cpages) {
                r = svm_migrate_copy_to_vram(adev, prange, &migrate, &mfence,
                                             scratch);
                migrate_vma_pages(&migrate);
                svm_migrate_copy_done(adev, mfence);
                migrate_vma_finalize(&migrate);
        }

        svm_range_dma_unmap(adev->dev, scratch, 0, npages);
        svm_range_free_dma_mappings(prange);

out_free:
        kvfree(buf);
out:
        if (!r) {
                pdd = svm_range_get_pdd_by_adev(prange, adev);
                if (pdd)
                        WRITE_ONCE(pdd->page_in, pdd->page_in + migrate.cpages);
        }

        return r;
}

/**
 * svm_migrate_ram_to_vram - migrate svm range from system to device
 * @prange: range structure
 * @best_loc: the device to migrate to
 * @mm: the process mm structure
 *
 * Context: Process context, caller hold mmap read lock, svms lock, prange lock
 *
 * Return:
 * 0 - OK, otherwise error code
 */
static int
svm_migrate_ram_to_vram(struct svm_range *prange, uint32_t best_loc,
                        struct mm_struct *mm)
{
        unsigned long addr, start, end;
        struct vm_area_struct *vma;
        struct amdgpu_device *adev;
        int r = 0;

        if (prange->actual_loc == best_loc) {
                pr_debug("svms 0x%p [0x%lx 0x%lx] already on best_loc 0x%x\n",
                         prange->svms, prange->start, prange->last, best_loc);
                return 0;
        }

        adev = svm_range_get_adev_by_id(prange, best_loc);
        if (!adev) {
                pr_debug("failed to get device by id 0x%x\n", best_loc);
                return -ENODEV;
        }

        pr_debug("svms 0x%p [0x%lx 0x%lx] to gpu 0x%x\n", prange->svms,
                 prange->start, prange->last, best_loc);

        /* FIXME: workaround for page locking bug with invalid pages */
        svm_range_prefault(prange, mm, SVM_ADEV_PGMAP_OWNER(adev));

        start = prange->start << PAGE_SHIFT;
        end = (prange->last + 1) << PAGE_SHIFT;

        for (addr = start; addr < end;) {
                unsigned long next;

                vma = find_vma(mm, addr);
                if (!vma || addr < vma->vm_start)
                        break;

                next = min(vma->vm_end, end);
                r = svm_migrate_vma_to_vram(adev, prange, vma, addr, next);
                if (r) {
                        pr_debug("failed to migrate\n");
                        break;
                }
                addr = next;
        }

        if (!r)
                prange->actual_loc = best_loc;

        return r;
}

static void svm_migrate_page_free(struct page *page)
{
        struct svm_range_bo *svm_bo = page->zone_device_data;

        if (svm_bo) {
                pr_debug("svm_bo ref left: %d\n", kref_read(&svm_bo->kref));
                svm_range_bo_unref(svm_bo);
        }
}

static int
svm_migrate_copy_to_ram(struct amdgpu_device *adev, struct svm_range *prange,
                        struct migrate_vma *migrate, struct dma_fence **mfence,
                        dma_addr_t *scratch, uint64_t npages)
{
        struct device *dev = adev->dev;
        uint64_t *src;
        dma_addr_t *dst;
        struct page *dpage;
        uint64_t i = 0, j;
        uint64_t addr;
        int r = 0;

        pr_debug("svms 0x%p [0x%lx 0x%lx]\n", prange->svms, prange->start,
                 prange->last);

        addr = prange->start << PAGE_SHIFT;

        src = (uint64_t *)(scratch + npages);
        dst = scratch;

        for (i = 0, j = 0; i < npages; i++, addr += PAGE_SIZE) {
                struct page *spage;

                spage = migrate_pfn_to_page(migrate->src[i]);
                if (!spage || !is_zone_device_page(spage)) {
                        pr_debug("invalid page. Could be in CPU already svms 0x%p [0x%lx 0x%lx]\n",
                                 prange->svms, prange->start, prange->last);
                        if (j) {
                                r = svm_migrate_copy_memory_gart(adev, dst + i - j,
                                                                 src + i - j, j,
                                                                 FROM_VRAM_TO_RAM,
                                                                 mfence);
                                if (r)
                                        goto out_oom;
                                j = 0;
                        }
                        continue;
                }
                src[i] = svm_migrate_addr(adev, spage);
                if (i > 0 && src[i] != src[i - 1] + PAGE_SIZE) {
                        r = svm_migrate_copy_memory_gart(adev, dst + i - j,
                                                         src + i - j, j,
                                                         FROM_VRAM_TO_RAM,
                                                         mfence);
                        if (r)
                                goto out_oom;
                        j = 0;
                }

                dpage = svm_migrate_get_sys_page(migrate->vma, addr);
                if (!dpage) {
                        pr_debug("failed get page svms 0x%p [0x%lx 0x%lx]\n",
                                 prange->svms, prange->start, prange->last);
                        r = -ENOMEM;
                        goto out_oom;
                }

                dst[i] = dma_map_page(dev, dpage, 0, PAGE_SIZE, DMA_FROM_DEVICE);
                r = dma_mapping_error(dev, dst[i]);
                if (r) {
                        pr_debug("failed %d dma_map_page\n", r);
                        goto out_oom;
                }

                pr_debug("dma mapping dst to 0x%llx, page_to_pfn 0x%lx\n",
                              dst[i] >> PAGE_SHIFT, page_to_pfn(dpage));

                migrate->dst[i] = migrate_pfn(page_to_pfn(dpage));
                migrate->dst[i] |= MIGRATE_PFN_LOCKED;
                j++;
        }

        r = svm_migrate_copy_memory_gart(adev, dst + i - j, src + i - j, j,
                                         FROM_VRAM_TO_RAM, mfence);

out_oom:
        if (r) {
                pr_debug("failed %d copy to ram\n", r);
                while (i--) {
                        svm_migrate_put_sys_page(dst[i]);
                        migrate->dst[i] = 0;
                }
        }

        return r;
}

static int
svm_migrate_vma_to_ram(struct amdgpu_device *adev, struct svm_range *prange,
                       struct vm_area_struct *vma, uint64_t start, uint64_t end)
{
        uint64_t npages = (end - start) >> PAGE_SHIFT;
        struct kfd_process_device *pdd;
        struct dma_fence *mfence = NULL;
        struct migrate_vma migrate;
        dma_addr_t *scratch;
        size_t size;
        void *buf;
        int r = -ENOMEM;

        memset(&migrate, 0, sizeof(migrate));
        migrate.vma = vma;
        migrate.start = start;
        migrate.end = end;
        migrate.flags = MIGRATE_VMA_SELECT_DEVICE_PRIVATE;
        migrate.pgmap_owner = SVM_ADEV_PGMAP_OWNER(adev);

        size = 2 * sizeof(*migrate.src) + sizeof(uint64_t) + sizeof(dma_addr_t);
        size *= npages;
        buf = kvmalloc(size, GFP_KERNEL | __GFP_ZERO);
        if (!buf)
                goto out;

        migrate.src = buf;
        migrate.dst = migrate.src + npages;
        scratch = (dma_addr_t *)(migrate.dst + npages);

        r = migrate_vma_setup(&migrate);
        if (r) {
                pr_debug("failed %d prepare migrate svms 0x%p [0x%lx 0x%lx]\n",
                         r, prange->svms, prange->start, prange->last);
                goto out_free;
        }

        pr_debug("cpages %ld\n", migrate.cpages);

        if (migrate.cpages) {
                r = svm_migrate_copy_to_ram(adev, prange, &migrate, &mfence,
                                            scratch, npages);
                migrate_vma_pages(&migrate);
                svm_migrate_copy_done(adev, mfence);
                migrate_vma_finalize(&migrate);
        } else {
                pr_debug("failed collect migrate device pages [0x%lx 0x%lx]\n",
                         prange->start, prange->last);
        }

        svm_range_dma_unmap(adev->dev, scratch, 0, npages);

out_free:
        kvfree(buf);
out:
        if (!r) {
                pdd = svm_range_get_pdd_by_adev(prange, adev);
                if (pdd)
                        WRITE_ONCE(pdd->page_out,
                                   pdd->page_out + migrate.cpages);
        }
        return r;
}

/**
 * svm_migrate_vram_to_ram - migrate svm range from device to system
 * @prange: range structure
 * @mm: process mm, use current->mm if NULL
 *
 * Context: Process context, caller hold mmap read lock, svms lock, prange lock
 *
 * Return:
 * 0 - OK, otherwise error code
 */
int svm_migrate_vram_to_ram(struct svm_range *prange, struct mm_struct *mm)
{
        struct amdgpu_device *adev;
        struct vm_area_struct *vma;
        unsigned long addr;
        unsigned long start;
        unsigned long end;
        int r = 0;

        if (!prange->actual_loc) {
                pr_debug("[0x%lx 0x%lx] already migrated to ram\n",
                         prange->start, prange->last);
                return 0;
        }

        adev = svm_range_get_adev_by_id(prange, prange->actual_loc);
        if (!adev) {
                pr_debug("failed to get device by id 0x%x\n",
                         prange->actual_loc);
                return -ENODEV;
        }

        pr_debug("svms 0x%p prange 0x%p [0x%lx 0x%lx] from gpu 0x%x to ram\n",
                 prange->svms, prange, prange->start, prange->last,
                 prange->actual_loc);

        start = prange->start << PAGE_SHIFT;
        end = (prange->last + 1) << PAGE_SHIFT;

        for (addr = start; addr < end;) {
                unsigned long next;

                vma = find_vma(mm, addr);
                if (!vma || addr < vma->vm_start)
                        break;

                next = min(vma->vm_end, end);
                r = svm_migrate_vma_to_ram(adev, prange, vma, addr, next);
                if (r) {
                        pr_debug("failed %d to migrate\n", r);
                        break;
                }
                addr = next;
        }

        if (!r) {
                svm_range_vram_node_free(prange);
                prange->actual_loc = 0;
        }
        return r;
}

/**
 * svm_migrate_vram_to_vram - migrate svm range from device to device
 * @prange: range structure
 * @best_loc: the device to migrate to
 * @mm: process mm, use current->mm if NULL
 *
 * Context: Process context, caller hold mmap read lock, svms lock, prange lock
 *
 * Return:
 * 0 - OK, otherwise error code
 */
static int
svm_migrate_vram_to_vram(struct svm_range *prange, uint32_t best_loc,
                         struct mm_struct *mm)
{
        int r;

        /*
         * TODO: for both devices with PCIe large bar or on same xgmi hive, skip
         * system memory as migration bridge
         */

        pr_debug("from gpu 0x%x to gpu 0x%x\n", prange->actual_loc, best_loc);

        r = svm_migrate_vram_to_ram(prange, mm);
        if (r)
                return r;

        return svm_migrate_ram_to_vram(prange, best_loc, mm);
}

int
svm_migrate_to_vram(struct svm_range *prange, uint32_t best_loc,
                    struct mm_struct *mm)
{
        if  (!prange->actual_loc)
                return svm_migrate_ram_to_vram(prange, best_loc, mm);
        else
                return svm_migrate_vram_to_vram(prange, best_loc, mm);

}

/**
 * svm_migrate_to_ram - CPU page fault handler
 * @vmf: CPU vm fault vma, address
 *
 * Context: vm fault handler, caller holds the mmap read lock
 *
 * Return:
 * 0 - OK
 * VM_FAULT_SIGBUS - notice application to have SIGBUS page fault
 */
static vm_fault_t svm_migrate_to_ram(struct vm_fault *vmf)
{
        unsigned long addr = vmf->address;
        struct vm_area_struct *vma;
        enum svm_work_list_ops op;
        struct svm_range *parent;
        struct svm_range *prange;
        struct kfd_process *p;
        struct mm_struct *mm;
        int r = 0;

        vma = vmf->vma;
        mm = vma->vm_mm;

        p = kfd_lookup_process_by_mm(vma->vm_mm);
        if (!p) {
                pr_debug("failed find process at fault address 0x%lx\n", addr);
                return VM_FAULT_SIGBUS;
        }
        addr >>= PAGE_SHIFT;
        pr_debug("CPU page fault svms 0x%p address 0x%lx\n", &p->svms, addr);

        mutex_lock(&p->svms.lock);

        prange = svm_range_from_addr(&p->svms, addr, &parent);
        if (!prange) {
                pr_debug("cannot find svm range at 0x%lx\n", addr);
                r = -EFAULT;
                goto out;
        }

        mutex_lock(&parent->migrate_mutex);
        if (prange != parent)
                mutex_lock_nested(&prange->migrate_mutex, 1);

        if (!prange->actual_loc)
                goto out_unlock_prange;

        svm_range_lock(parent);
        if (prange != parent)
                mutex_lock_nested(&prange->lock, 1);
        r = svm_range_split_by_granularity(p, mm, addr, parent, prange);
        if (prange != parent)
                mutex_unlock(&prange->lock);
        svm_range_unlock(parent);
        if (r) {
                pr_debug("failed %d to split range by granularity\n", r);
                goto out_unlock_prange;
        }

        r = svm_migrate_vram_to_ram(prange, mm);
        if (r)
                pr_debug("failed %d migrate 0x%p [0x%lx 0x%lx] to ram\n", r,
                         prange, prange->start, prange->last);

        /* xnack on, update mapping on GPUs with ACCESS_IN_PLACE */
        if (p->xnack_enabled && parent == prange)
                op = SVM_OP_UPDATE_RANGE_NOTIFIER_AND_MAP;
        else
                op = SVM_OP_UPDATE_RANGE_NOTIFIER;
        svm_range_add_list_work(&p->svms, parent, mm, op);
        schedule_deferred_list_work(&p->svms);

out_unlock_prange:
        if (prange != parent)
                mutex_unlock(&prange->migrate_mutex);
        mutex_unlock(&parent->migrate_mutex);
out:
        mutex_unlock(&p->svms.lock);
        kfd_unref_process(p);

        pr_debug("CPU fault svms 0x%p address 0x%lx done\n", &p->svms, addr);

        return r ? VM_FAULT_SIGBUS : 0;
}

static const struct dev_pagemap_ops svm_migrate_pgmap_ops = {
        .page_free              = svm_migrate_page_free,
        .migrate_to_ram         = svm_migrate_to_ram,
};

/* Each VRAM page uses sizeof(struct page) on system memory */
#define SVM_HMM_PAGE_STRUCT_SIZE(size) ((size)/PAGE_SIZE * sizeof(struct page))

int svm_migrate_init(struct amdgpu_device *adev)
{
        struct kfd_dev *kfddev = adev->kfd.dev;
        struct dev_pagemap *pgmap;
        struct resource *res;
        unsigned long size;
        void *r;

        /* Page migration works on Vega10 or newer */
        if (kfddev->device_info->asic_family < CHIP_VEGA10)
                return -EINVAL;

        pgmap = &kfddev->pgmap;
        memset(pgmap, 0, sizeof(*pgmap));

        /* TODO: register all vram to HMM for now.
         * should remove reserved size
         */
        size = ALIGN(adev->gmc.real_vram_size, 2ULL << 20);
        res = devm_request_free_mem_region(adev->dev, &iomem_resource, size);
        if (IS_ERR(res))
                return -ENOMEM;

        pgmap->type = MEMORY_DEVICE_PRIVATE;
        pgmap->nr_range = 1;
        pgmap->range.start = res->start;
        pgmap->range.end = res->end;
        pgmap->ops = &svm_migrate_pgmap_ops;
        pgmap->owner = SVM_ADEV_PGMAP_OWNER(adev);
        pgmap->flags = MIGRATE_VMA_SELECT_DEVICE_PRIVATE;

        /* Device manager releases device-specific resources, memory region and
         * pgmap when driver disconnects from device.
         */
        r = devm_memremap_pages(adev->dev, pgmap);
        if (IS_ERR(r)) {
                pr_err("failed to register HMM device memory\n");

                /* Disable SVM support capability */
                pgmap->type = 0;
                devm_release_mem_region(adev->dev, res->start,
                                        res->end - res->start + 1);
                return PTR_ERR(r);
        }

        pr_debug("reserve %ldMB system memory for VRAM pages struct\n",
                 SVM_HMM_PAGE_STRUCT_SIZE(size) >> 20);

        amdgpu_amdkfd_reserve_system_mem(SVM_HMM_PAGE_STRUCT_SIZE(size));

        pr_info("HMM registered %ldMB device memory\n", size >> 20);

        return 0;
}