[PATCH] drm/amdgpu: Add notifier lock for KFD userptrs

Chen, Xiaogang Xiaogang.Chen at amd.com
Thu Nov 17 22:30:33 UTC 2022


[AMD Official Use Only - General]

This patch is:
Reviewed-by: Xiaogang Chen<Xiaogang.Chen at amd.com>

-----Original Message-----
From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> On Behalf Of Felix Kuehling
Sent: Wednesday, November 2, 2022 9:00 PM
To: amd-gfx at lists.freedesktop.org
Subject: [PATCH] drm/amdgpu: Add notifier lock for KFD userptrs

Caution: This message originated from an External Source. Use proper caution when opening attachments, clicking links, or responding.


Add a per-process MMU notifier lock for processing notifiers from userptrs. Use that lock to properly synchronize page table updates with MMU notifiers.

Signed-off-by: Felix Kuehling <Felix.Kuehling at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h    |  12 +-
 .../gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c  | 202 +++++++++++-------
 drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c        |  12 +-
 drivers/gpu/drm/amd/amdgpu/amdgpu_mn.h        |   3 +-
 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c       |  18 +-
 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h       |   4 +
 6 files changed, 158 insertions(+), 93 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h
index f50e3ba4d7a5..1ca18a77818b 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h
@@ -29,6 +29,7 @@
 #include <linux/mm.h>
 #include <linux/kthread.h>
 #include <linux/workqueue.h>
+#include <linux/mmu_notifier.h>
 #include <kgd_kfd_interface.h>
 #include <drm/ttm/ttm_execbuf_util.h>
 #include "amdgpu_sync.h"
@@ -75,7 +76,7 @@ struct kgd_mem {

        uint32_t alloc_flags;

-       atomic_t invalid;
+       uint32_t invalid;
        struct amdkfd_process_info *process_info;

        struct amdgpu_sync sync;
@@ -131,7 +132,8 @@ struct amdkfd_process_info {
        struct amdgpu_amdkfd_fence *eviction_fence;

        /* MMU-notifier related fields */
-       atomic_t evicted_bos;
+       struct mutex notifier_lock;
+       uint32_t evicted_bos;
        struct delayed_work restore_userptr_work;
        struct pid *pid;
        bool block_mmu_notifications;
@@ -180,7 +182,8 @@ int kfd_debugfs_kfd_mem_limits(struct seq_file *m, void *data);  bool amdkfd_fence_check_mm(struct dma_fence *f, struct mm_struct *mm);  struct amdgpu_amdkfd_fence *to_amdgpu_amdkfd_fence(struct dma_fence *f);  int amdgpu_amdkfd_remove_fence_on_pt_pd_bos(struct amdgpu_bo *bo); -int amdgpu_amdkfd_evict_userptr(struct kgd_mem *mem, struct mm_struct *mm);
+int amdgpu_amdkfd_evict_userptr(struct mmu_interval_notifier *mni,
+                               unsigned long cur_seq, struct kgd_mem 
+*mem);
 #else
 static inline
 bool amdkfd_fence_check_mm(struct dma_fence *f, struct mm_struct *mm) @@ -201,7 +204,8 @@ int amdgpu_amdkfd_remove_fence_on_pt_pd_bos(struct amdgpu_bo *bo)  }

 static inline
-int amdgpu_amdkfd_evict_userptr(struct kgd_mem *mem, struct mm_struct *mm)
+int amdgpu_amdkfd_evict_userptr(struct mmu_interval_notifier *mni,
+                               unsigned long cur_seq, struct kgd_mem 
+*mem)
 {
        return 0;
 }
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
index 955fa8c8213b..5510b7c42ac7 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
@@ -964,7 +964,9 @@ static int init_user_pages(struct kgd_mem *mem, uint64_t user_addr,
                 * later stage when it is scheduled by another ioctl called by
                 * CRIU master process for the target pid for restore.
                 */
-               atomic_inc(&mem->invalid);
+               mutex_lock(&process_info->notifier_lock);
+               mem->invalid++;
+               mutex_unlock(&process_info->notifier_lock);
                mutex_unlock(&process_info->lock);
                return 0;
        }
@@ -1301,6 +1303,7 @@ static int init_kfd_vm(struct amdgpu_vm *vm, void **process_info,
                        return -ENOMEM;

                mutex_init(&info->lock);
+               mutex_init(&info->notifier_lock);
                INIT_LIST_HEAD(&info->vm_list_head);
                INIT_LIST_HEAD(&info->kfd_bo_list);
                INIT_LIST_HEAD(&info->userptr_valid_list);
@@ -1317,7 +1320,6 @@ static int init_kfd_vm(struct amdgpu_vm *vm, void **process_info,
                }

                info->pid = get_task_pid(current->group_leader, PIDTYPE_PID);
-               atomic_set(&info->evicted_bos, 0);
                INIT_DELAYED_WORK(&info->restore_userptr_work,
                                  amdgpu_amdkfd_restore_userptr_worker);

@@ -1372,6 +1374,7 @@ static int init_kfd_vm(struct amdgpu_vm *vm, void **process_info,
                put_pid(info->pid);
 create_evict_fence_fail:
                mutex_destroy(&info->lock);
+               mutex_destroy(&info->notifier_lock);
                kfree(info);
        }
        return ret;
@@ -1496,6 +1499,7 @@ void amdgpu_amdkfd_gpuvm_destroy_cb(struct amdgpu_device *adev,
                cancel_delayed_work_sync(&process_info->restore_userptr_work);
                put_pid(process_info->pid);
                mutex_destroy(&process_info->lock);
+               mutex_destroy(&process_info->notifier_lock);
                kfree(process_info);
        }
 }
@@ -1548,7 +1552,9 @@ int amdgpu_amdkfd_criu_resume(void *p)

        mutex_lock(&pinfo->lock);
        pr_debug("scheduling work\n");
-       atomic_inc(&pinfo->evicted_bos);
+       mutex_lock(&pinfo->notifier_lock);
+       pinfo->evicted_bos++;
+       mutex_unlock(&pinfo->notifier_lock);
        if (!READ_ONCE(pinfo->block_mmu_notifications)) {
                ret = -EINVAL;
                goto out_unlock;
@@ -1773,8 +1779,13 @@ int amdgpu_amdkfd_gpuvm_free_memory_of_gpu(
        list_del(&bo_list_entry->head);
        mutex_unlock(&process_info->lock);

-       /* No more MMU notifiers */
-       amdgpu_mn_unregister(mem->bo);
+       /* Cleanup user pages and MMU notifiers */
+       if (amdgpu_ttm_tt_get_usermm(mem->bo->tbo.ttm)) {
+               amdgpu_mn_unregister(mem->bo);
+               mutex_lock(&process_info->notifier_lock);
+               amdgpu_ttm_tt_discard_user_pages(mem->bo->tbo.ttm);
+               mutex_unlock(&process_info->notifier_lock);
+       }

        ret = reserve_bo_and_cond_vms(mem, NULL, BO_VM_ALL, &ctx);
        if (unlikely(ret))
@@ -1864,14 +1875,14 @@ int amdgpu_amdkfd_gpuvm_map_memory_to_gpu(
         */
        mutex_lock(&mem->process_info->lock);

-       /* Lock mmap-sem. If we find an invalid userptr BO, we can be
+       /* Lock notifier lock. If we find an invalid userptr BO, we can 
+ be
         * sure that the MMU notifier is no longer running
         * concurrently and the queues are actually stopped
         */
        if (amdgpu_ttm_tt_get_usermm(bo->tbo.ttm)) {
-               mmap_write_lock(current->mm);
-               is_invalid_userptr = atomic_read(&mem->invalid);
-               mmap_write_unlock(current->mm);
+               mutex_lock(&mem->process_info->notifier_lock);
+               is_invalid_userptr = !!mem->invalid;
+               mutex_unlock(&mem->process_info->notifier_lock);
        }

        mutex_lock(&mem->lock);
@@ -2251,34 +2262,38 @@ int amdgpu_amdkfd_gpuvm_import_dmabuf(struct amdgpu_device *adev,
  *
  * Runs in MMU notifier, may be in RECLAIM_FS context. This means it
  * cannot do any memory allocations, and cannot take any locks that
- * are held elsewhere while allocating memory. Therefore this is as
- * simple as possible, using atomic counters.
+ * are held elsewhere while allocating memory.
  *
  * It doesn't do anything to the BO itself. The real work happens in
  * restore, where we get updated page addresses. This function only
  * ensures that GPU access to the BO is stopped.
  */
-int amdgpu_amdkfd_evict_userptr(struct kgd_mem *mem,
-                               struct mm_struct *mm)
+int amdgpu_amdkfd_evict_userptr(struct mmu_interval_notifier *mni,
+                               unsigned long cur_seq, struct kgd_mem 
+*mem)
 {
        struct amdkfd_process_info *process_info = mem->process_info;
-       int evicted_bos;
        int r = 0;

-       /* Do not process MMU notifications until stage-4 IOCTL is received */
+       /* Do not process MMU notifications during CRIU restore until
+        * KFD_CRIU_OP_RESUME IOCTL is received
+        */
        if (READ_ONCE(process_info->block_mmu_notifications))
                return 0;

-       atomic_inc(&mem->invalid);
-       evicted_bos = atomic_inc_return(&process_info->evicted_bos);
-       if (evicted_bos == 1) {
+       mutex_lock(&process_info->notifier_lock);
+       mmu_interval_set_seq(mni, cur_seq);
+
+       mem->invalid++;
+       if (++process_info->evicted_bos == 1) {
                /* First eviction, stop the queues */
-               r = kgd2kfd_quiesce_mm(mm, KFD_QUEUE_EVICTION_TRIGGER_USERPTR);
+               r = kgd2kfd_quiesce_mm(mni->mm,
+                                      
+ KFD_QUEUE_EVICTION_TRIGGER_USERPTR);
                if (r)
                        pr_err("Failed to quiesce KFD\n");
                schedule_delayed_work(&process_info->restore_userptr_work,
                        msecs_to_jiffies(AMDGPU_USERPTR_RESTORE_DELAY_MS));
        }
+       mutex_unlock(&process_info->notifier_lock);

        return r;
 }
@@ -2295,49 +2310,54 @@ static int update_invalid_user_pages(struct amdkfd_process_info *process_info,
        struct kgd_mem *mem, *tmp_mem;
        struct amdgpu_bo *bo;
        struct ttm_operation_ctx ctx = { false, false };
-       int invalid, ret;
+       uint32_t invalid;
+       int ret = 0;

-       /* Move all invalidated BOs to the userptr_inval_list and
-        * release their user pages by migration to the CPU domain
-        */
+       mutex_lock(&process_info->notifier_lock);
+
+       /* Move all invalidated BOs to the userptr_inval_list */
        list_for_each_entry_safe(mem, tmp_mem,
                                 &process_info->userptr_valid_list,
-                                validate_list.head) {
-               if (!atomic_read(&mem->invalid))
-                       continue; /* BO is still valid */
-
-               bo = mem->bo;
-
-               if (amdgpu_bo_reserve(bo, true))
-                       return -EAGAIN;
-               amdgpu_bo_placement_from_domain(bo, AMDGPU_GEM_DOMAIN_CPU);
-               ret = ttm_bo_validate(&bo->tbo, &bo->placement, &ctx);
-               amdgpu_bo_unreserve(bo);
-               if (ret) {
-                       pr_err("%s: Failed to invalidate userptr BO\n",
-                              __func__);
-                       return -EAGAIN;
-               }
-
-               list_move_tail(&mem->validate_list.head,
-                              &process_info->userptr_inval_list);
-       }
-
-       if (list_empty(&process_info->userptr_inval_list))
-               return 0; /* All evicted userptr BOs were freed */
+                                validate_list.head)
+               if (mem->invalid)
+                       list_move_tail(&mem->validate_list.head,
+                                      
+ &process_info->userptr_inval_list);

        /* Go through userptr_inval_list and update any invalid user_pages */
        list_for_each_entry(mem, &process_info->userptr_inval_list,
                            validate_list.head) {
-               invalid = atomic_read(&mem->invalid);
+               invalid = mem->invalid;
                if (!invalid)
                        /* BO hasn't been invalidated since the last
-                        * revalidation attempt. Keep its BO list.
+                        * revalidation attempt. Keep its page list.
                         */
                        continue;

                bo = mem->bo;

+               amdgpu_ttm_tt_discard_user_pages(bo->tbo.ttm);
+
+               /* BO reservations and getting user pages (hmm_range_fault)
+                * must happen outside the notifier lock
+                */
+               mutex_unlock(&process_info->notifier_lock);
+
+               /* Move the BO to system (CPU) domain if necessary to unmap
+                * and free the SG table
+                */
+               if (bo->tbo.resource->mem_type != TTM_PL_SYSTEM) {
+                       if (amdgpu_bo_reserve(bo, true))
+                               return -EAGAIN;
+                       amdgpu_bo_placement_from_domain(bo, AMDGPU_GEM_DOMAIN_CPU);
+                       ret = ttm_bo_validate(&bo->tbo, &bo->placement, &ctx);
+                       amdgpu_bo_unreserve(bo);
+                       if (ret) {
+                               pr_err("%s: Failed to invalidate userptr BO\n",
+                                      __func__);
+                               return -EAGAIN;
+                       }
+               }
+
                /* Get updated user pages */
                ret = amdgpu_ttm_tt_get_user_pages(bo, bo->tbo.ttm->pages);
                if (ret) {
@@ -2352,30 +2372,31 @@ static int update_invalid_user_pages(struct amdkfd_process_info *process_info,
                         */
                        if (ret != -EFAULT)
                                return ret;
-               } else {
-
-                       /*
-                        * FIXME: Cannot ignore the return code, must hold
-                        * notifier_lock
-                        */
-                       amdgpu_ttm_tt_get_user_pages_done(bo->tbo.ttm);
+                       ret = 0;
                }

+               mutex_lock(&process_info->notifier_lock);
+
                /* Mark the BO as valid unless it was invalidated
                 * again concurrently.
                 */
-               if (atomic_cmpxchg(&mem->invalid, invalid, 0) != invalid)
-                       return -EAGAIN;
+               if (mem->invalid != invalid) {
+                       ret = -EAGAIN;
+                       goto unlock_out;
+               }
+               mem->invalid = 0;
        }

-       return 0;
+unlock_out:
+       mutex_unlock(&process_info->notifier_lock);
+
+       return ret;
 }

 /* Validate invalid userptr BOs
  *
- * Validates BOs on the userptr_inval_list, and moves them back to the
- * userptr_valid_list. Also updates GPUVM page tables with new page
- * addresses and waits for the page table updates to complete.
+ * Validates BOs on the userptr_inval_list. Also updates GPUVM page 
+ tables
+ * with new page addresses and waits for the page table updates to complete.
  */
 static int validate_invalid_user_pages(struct amdkfd_process_info *process_info)  { @@ -2446,9 +2467,6 @@ static int validate_invalid_user_pages(struct amdkfd_process_info *process_info)
                        }
                }

-               list_move_tail(&mem->validate_list.head,
-                              &process_info->userptr_valid_list);
-
                /* Update mapping. If the BO was not validated
                 * (because we couldn't get user pages), this will
                 * clear the page table entries, which will result in @@ -2464,7 +2482,9 @@ static int validate_invalid_user_pages(struct amdkfd_process_info *process_info)
                        if (ret) {
                                pr_err("%s: update PTE failed\n", __func__);
                                /* make sure this gets validated again */
-                               atomic_inc(&mem->invalid);
+                               mutex_lock(&process_info->notifier_lock);
+                               mem->invalid++;
+                               
+ mutex_unlock(&process_info->notifier_lock);
                                goto unreserve_out;
                        }
                }
@@ -2484,6 +2504,32 @@ static int validate_invalid_user_pages(struct amdkfd_process_info *process_info)
        return ret;
 }

+/* Confirm that all user pages are valid while holding the notifier 
+lock
+ *
+ * Moves valid BOs from the userptr_inval_list back to userptr_val_list.
+ */
+static int confirm_valid_user_pages_locked(struct amdkfd_process_info 
+*process_info) {
+       struct kgd_mem *mem, *tmp_mem;
+       int ret = 0;
+
+       list_for_each_entry_safe(mem, tmp_mem,
+                                &process_info->userptr_inval_list,
+                                validate_list.head) {
+               if (!amdgpu_ttm_tt_get_user_pages_done(mem->bo->tbo.ttm)) {
+                       WARN(!mem->invalid, "Invalid BO not marked invalid");
+                       ret = -EAGAIN;
+                       continue;
+               }
+               WARN(mem->invalid, "Valid BO is marked invalid");
+
+               list_move_tail(&mem->validate_list.head,
+                              &process_info->userptr_valid_list);
+       }
+
+       return ret;
+}
+
 /* Worker callback to restore evicted userptr BOs
  *
  * Tries to update and validate all userptr BOs. If successful and no @@ -2498,9 +2544,11 @@ static void amdgpu_amdkfd_restore_userptr_worker(struct work_struct *work)
                             restore_userptr_work);
        struct task_struct *usertask;
        struct mm_struct *mm;
-       int evicted_bos;
+       uint32_t evicted_bos;

-       evicted_bos = atomic_read(&process_info->evicted_bos);
+       mutex_lock(&process_info->notifier_lock);
+       evicted_bos = process_info->evicted_bos;
+       mutex_unlock(&process_info->notifier_lock);
        if (!evicted_bos)
                return;

@@ -2523,9 +2571,6 @@ static void amdgpu_amdkfd_restore_userptr_worker(struct work_struct *work)
         * and we can just restart the queues.
         */
        if (!list_empty(&process_info->userptr_inval_list)) {
-               if (atomic_read(&process_info->evicted_bos) != evicted_bos)
-                       goto unlock_out; /* Concurrent eviction, try again */
-
                if (validate_invalid_user_pages(process_info))
                        goto unlock_out;
        }
@@ -2534,10 +2579,17 @@ static void amdgpu_amdkfd_restore_userptr_worker(struct work_struct *work)
         * be a first eviction that calls quiesce_mm. The eviction
         * reference counting inside KFD will handle this case.
         */
-       if (atomic_cmpxchg(&process_info->evicted_bos, evicted_bos, 0) !=
-           evicted_bos)
-               goto unlock_out;
-       evicted_bos = 0;
+       mutex_lock(&process_info->notifier_lock);
+       if (process_info->evicted_bos != evicted_bos)
+               goto unlock_notifier_out;
+
+       if (confirm_valid_user_pages_locked(process_info)) {
+               WARN(1, "User pages unexpectedly invalid");
+               goto unlock_notifier_out;
+       }
+
+       process_info->evicted_bos = evicted_bos = 0;
+
        if (kgd2kfd_resume_mm(mm)) {
                pr_err("%s: Failed to resume KFD\n", __func__);
                /* No recovery from this failure. Probably the CP is @@ -2545,6 +2597,8 @@ static void amdgpu_amdkfd_restore_userptr_worker(struct work_struct *work)
                 */
        }

+unlock_notifier_out:
+       mutex_unlock(&process_info->notifier_lock);
 unlock_out:
        mutex_unlock(&process_info->lock);

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c
index b86c0b8252a5..93b6a2a7d64c 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c
@@ -102,17 +102,11 @@ static bool amdgpu_mn_invalidate_hsa(struct mmu_interval_notifier *mni,
                                     unsigned long cur_seq)  {
        struct amdgpu_bo *bo = container_of(mni, struct amdgpu_bo, notifier);
-       struct amdgpu_device *adev = amdgpu_ttm_adev(bo->tbo.bdev);

        if (!mmu_notifier_range_blockable(range))
                return false;

-       mutex_lock(&adev->notifier_lock);
-
-       mmu_interval_set_seq(mni, cur_seq);
-
-       amdgpu_amdkfd_evict_userptr(bo->kfd_bo, bo->notifier.mm);
-       mutex_unlock(&adev->notifier_lock);
+       amdgpu_amdkfd_evict_userptr(mni, cur_seq, bo->kfd_bo);

        return true;
 }
@@ -231,9 +225,9 @@ int amdgpu_hmm_range_get_pages(struct mmu_interval_notifier *notifier,
        return r;
 }

-int amdgpu_hmm_range_get_pages_done(struct hmm_range *hmm_range)
+bool amdgpu_hmm_range_get_pages_done(struct hmm_range *hmm_range)
 {
-       int r;
+       bool r;

        r = mmu_interval_read_retry(hmm_range->notifier,
                                    hmm_range->notifier_seq); diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.h
index 14a3c1864085..b37fcf99baf1 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.h
@@ -29,13 +29,14 @@
 #include <linux/rwsem.h>
 #include <linux/workqueue.h>
 #include <linux/interval_tree.h>
+#include <linux/mmu_notifier.h>

 int amdgpu_hmm_range_get_pages(struct mmu_interval_notifier *notifier,
                               struct mm_struct *mm, struct page **pages,
                               uint64_t start, uint64_t npages,
                               struct hmm_range **phmm_range, bool readonly,
                               bool mmap_locked, void *owner); -int amdgpu_hmm_range_get_pages_done(struct hmm_range *hmm_range);
+bool amdgpu_hmm_range_get_pages_done(struct hmm_range *hmm_range);

 #if defined(CONFIG_HMM_MIRROR)
 int amdgpu_mn_register(struct amdgpu_bo *bo, unsigned long addr); diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index 585460ab8dfd..5f2b87dd5732 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -706,8 +706,20 @@ int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo, struct page **pages)
        return r;
 }

+/* amdgpu_ttm_tt_discard_user_pages - Discard range and pfn array 
+allocations  */ void amdgpu_ttm_tt_discard_user_pages(struct ttm_tt 
+*ttm) {
+       struct amdgpu_ttm_tt *gtt = (void *)ttm;
+
+       if (gtt && gtt->userptr && gtt->range) {
+               amdgpu_hmm_range_get_pages_done(gtt->range);
+               gtt->range = NULL;
+       }
+}
+
 /*
- * amdgpu_ttm_tt_userptr_range_done - stop HMM track the CPU page table change
+ * amdgpu_ttm_tt_get_user_pages_done - stop HMM track the CPU page 
+ table change
  * Check if the pages backing this ttm range have been invalidated
  *
  * Returns: true if pages are still valid @@ -727,10 +739,6 @@ bool amdgpu_ttm_tt_get_user_pages_done(struct ttm_tt *ttm)
                "No user pages to check\n");

        if (gtt->range) {
-               /*
-                * FIXME: Must always hold notifier_lock for this, and must
-                * not ignore the return code.
-                */
                r = amdgpu_hmm_range_get_pages_done(gtt->range);
                gtt->range = NULL;
        }
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
index 9120ae80ef52..58b70d862437 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
@@ -158,6 +158,7 @@ uint64_t amdgpu_ttm_domain_start(struct amdgpu_device *adev, uint32_t type);

 #if IS_ENABLED(CONFIG_DRM_AMDGPU_USERPTR)
 int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo, struct page **pages);
+void amdgpu_ttm_tt_discard_user_pages(struct ttm_tt *ttm);
 bool amdgpu_ttm_tt_get_user_pages_done(struct ttm_tt *ttm);  #else  static inline int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo, @@ -165,6 +166,9 @@ static inline int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo,  {
        return -EPERM;
 }
+static void amdgpu_ttm_tt_discard_user_pages(struct ttm_tt *ttm) { }
 static inline bool amdgpu_ttm_tt_get_user_pages_done(struct ttm_tt *ttm)  {
        return false;
--
2.32.0


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