Re: [Patch v2 1/2] drm/amdgpu: use user provided hmm_range buffer in amdgpu_ttm_tt_get_user_pages

Fri, 17 Oct 2025 14:08:27 -0700 


On 10/4/2025 1:53 AM, Chen, Xiaogang wrote:


On 9/26/2025 5:53 AM, Khatri, Sunil wrote:


On 9/24/2025 10:27 PM, Kuehling, Felix wrote:

On 2025-09-24 06:01, Sunil Khatri wrote:

update the amdgpu_ttm_tt_get_user_pages and all dependent function
along with it callers to use a user allocated hmm_range buffer instead
hmm layer allocates the buffer.

This is a need to get hmm_range pointers easily accessible
without accessing the bo and that is a requirement for the
userqueue to lock the userptrs effectively.

Signed-off-by: Sunil Khatri <[email protected]>



What's the reason for this change? In the current code, the 
hmm_range is allocated by amdgpu_hmm_range_get_pages and freed by 
amdgpu_hmm_range_get_pages_done. Your change is breaking that symmetry.

Sorry i missed your comment. For userqueues locking the userptr bos 
and making sure we have valid userptrs at the time of validation 
seems too complicated, so along with christian we decided to use 
hmm_range list instead and have reference to userptr bo and via 
hmm_range private field to be set to bo.



Also i did made sure that wherever we are doing get pages and 
allocating range the freeing part is taken care of. Specially for 
freeing the memory is still done by amdgpu_hmm_range_get_pages_done 
only. Please share if anywhere i missed something. Also Christian 
brought out the point to have separate alloc/free for hmm_range which 
i am working on and will share soon.



This patch has other components to allocate hmm_range, freed it at 
amdgpu_hmm_range_get_pages_done. This inconsistency makes other 
components handle error case awkward.  It is better to let other 
component free hmm_range no matter amdgpu_hmm_range_get_pages success 
or not. And amdgpu_hmm_range_get_pages(done) alloc/free 
hmm_range->hmm_pfns. That would be easy to understand and have less 
chance to make mistake.

Yes, that inconsistency is there and that is to be fixed is taken care 
by having separate alloc/free functions and not use 
amdgpu_hmm_range_get_pages_done and some more clean up done in other 
patch since this code is already merged.


Regards
Sunil khatri



Regards

Xiaogang



Regards
Sunil Khatri


Regards,
  Felix



---

  drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c | 16 
++++++++++++++--

  drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c           |  6 +++++-
  drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c          | 10 +++++++---
  drivers/gpu/drm/amd/amdgpu/amdgpu_hmm.c          | 11 +----------
  drivers/gpu/drm/amd/amdgpu/amdgpu_hmm.h          |  2 +-
  drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c          |  8 +++-----
  drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h          |  4 ++--
  drivers/gpu/drm/amd/amdkfd/kfd_svm.c             |  7 +++++--
  8 files changed, 38 insertions(+), 26 deletions(-)


diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c

index 7c54fe6b0f5d..4babd37712fb 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c

@@ -1089,8 +1089,15 @@ static int init_user_pages(struct kgd_mem 
*mem, uint64_t user_addr,

          return 0;
      }
  -    ret = amdgpu_ttm_tt_get_user_pages(bo, &range);
+    range = kzalloc(sizeof(*range), GFP_KERNEL);
+    if (unlikely(!range)) {
+        ret = -ENOMEM;
+        goto unregister_out;
+    }
+
+    ret = amdgpu_ttm_tt_get_user_pages(bo, range);
      if (ret) {
+        kfree(range);
          if (ret == -EAGAIN)
              pr_debug("Failed to get user pages, try again\n");
          else

@@ -2567,9 +2574,14 @@ static int update_invalid_user_pages(struct 
amdkfd_process_info *process_info,

              }
          }
  +        mem->range = kzalloc(sizeof(*mem->range), GFP_KERNEL);
+        if (unlikely(!mem->range))
+            return -ENOMEM;
          /* Get updated user pages */
-        ret = amdgpu_ttm_tt_get_user_pages(bo, &mem->range);
+        ret = amdgpu_ttm_tt_get_user_pages(bo, mem->range);
          if (ret) {
+            kfree(mem->range);
+            mem->range = NULL;
              pr_debug("Failed %d to get user pages\n", ret);

                /* Return -EFAULT bad address error as success. It 
will
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c

index 744e6ff69814..31eea1c7dac3 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c

@@ -884,9 +884,13 @@ static int amdgpu_cs_parser_bos(struct 
amdgpu_cs_parser *p,

      amdgpu_bo_list_for_each_userptr_entry(e, p->bo_list) {
          bool userpage_invalidated = false;
          struct amdgpu_bo *bo = e->bo;
+        e->range = kzalloc(sizeof(*e->range), GFP_KERNEL);
+        if (unlikely(!e->range))
+            return -ENOMEM;
+
          int i;
  -        r = amdgpu_ttm_tt_get_user_pages(bo, &e->range);
+        r = amdgpu_ttm_tt_get_user_pages(bo, e->range);
          if (r)
              goto out_free_user_pages;

  diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c

index 8524aa55e057..12f0597a3659 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c

@@ -571,10 +571,14 @@ int amdgpu_gem_userptr_ioctl(struct 
drm_device *dev, void *data,

          goto release_object;
        if (args->flags & AMDGPU_GEM_USERPTR_VALIDATE) {
-        r = amdgpu_ttm_tt_get_user_pages(bo, &range);
-        if (r)
+        range = kzalloc(sizeof(*range), GFP_KERNEL);
+        if (unlikely(!range))
+            return -ENOMEM;
+        r = amdgpu_ttm_tt_get_user_pages(bo, range);
+        if (r) {
+            kfree(range);
              goto release_object;
-
+        }
          r = amdgpu_bo_reserve(bo, true);
          if (r)
              goto user_pages_done;

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_hmm.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_hmm.c

index 2c6a6b858112..53d405a92a14 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_hmm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_hmm.c
@@ -168,18 +168,13 @@ void amdgpu_hmm_unregister(struct amdgpu_bo *bo)

  int amdgpu_hmm_range_get_pages(struct mmu_interval_notifier 
*notifier,

                     uint64_t start, uint64_t npages, bool readonly,
                     void *owner,
-                   struct hmm_range **phmm_range)
+                   struct hmm_range *hmm_range)
  {
-    struct hmm_range *hmm_range;
      unsigned long end;
      unsigned long timeout;
      unsigned long *pfns;
      int r = 0;
  -    hmm_range = kzalloc(sizeof(*hmm_range), GFP_KERNEL);
-    if (unlikely(!hmm_range))
-        return -ENOMEM;
-
      pfns = kvmalloc_array(npages, sizeof(*pfns), GFP_KERNEL);
      if (unlikely(!pfns)) {
          r = -ENOMEM;

@@ -221,15 +216,11 @@ int amdgpu_hmm_range_get_pages(struct 
mmu_interval_notifier *notifier,

      hmm_range->start = start;
      hmm_range->hmm_pfns = pfns;
  -    *phmm_range = hmm_range;
-
      return 0;
    out_free_pfns:
      kvfree(pfns);
  out_free_range:
-    kfree(hmm_range);
-
      if (r == -EBUSY)
          r = -EAGAIN;
      return r;

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_hmm.h 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_hmm.h

index 953e1d06de20..c54e3c64251a 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_hmm.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_hmm.h
@@ -34,7 +34,7 @@

  int amdgpu_hmm_range_get_pages(struct mmu_interval_notifier 
*notifier,

                     uint64_t start, uint64_t npages, bool readonly,
                     void *owner,
-                   struct hmm_range **phmm_range);
+                   struct hmm_range *hmm_range);
  bool amdgpu_hmm_range_get_pages_done(struct hmm_range *hmm_range);
    #if defined(CONFIG_HMM_MIRROR)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c

index 901e0c39a594..046ff2346dab 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -705,10 +705,11 @@ struct amdgpu_ttm_tt {
   * memory and start HMM tracking CPU page table update
   *

   * Calling function must call amdgpu_ttm_tt_userptr_range_done() 
once and only

- * once afterwards to stop HMM tracking

+ * once afterwards to stop HMM tracking. Its the caller 
responsibility to ensure

+ * that range is a valid memory and it is freed too.
   */
  int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo,
-                 struct hmm_range **range)
+                 struct hmm_range *range)
  {
      struct ttm_tt *ttm = bo->tbo.ttm;
      struct amdgpu_ttm_tt *gtt = ttm_to_amdgpu_ttm_tt(ttm);

@@ -718,9 +719,6 @@ int amdgpu_ttm_tt_get_user_pages(struct 
amdgpu_bo *bo,

      bool readonly;
      int r = 0;
  -    /* Make sure get_user_pages_done() can cleanup gracefully */
-    *range = NULL;
-
      mm = bo->notifier.mm;
      if (unlikely(!mm)) {
          DRM_DEBUG_DRIVER("BO is not registered?\n");

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h

index 6ac94469ed40..a8379b925878 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h

@@ -191,14 +191,14 @@ 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 hmm_range **range);
+                 struct hmm_range *range);
  void amdgpu_ttm_tt_discard_user_pages(struct ttm_tt *ttm,
                        struct hmm_range *range);
  bool amdgpu_ttm_tt_get_user_pages_done(struct ttm_tt *ttm,
                         struct hmm_range *range);
  #else
  static inline int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo,
-                           struct hmm_range **range)
+                           struct hmm_range *range)
  {
      return -EPERM;
  }

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c 
b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c

index 273f42e3afdd..9f0f14ea93e5 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c

@@ -1737,12 +1737,15 @@ static int 
svm_range_validate_and_map(struct mm_struct *mm,

              }
                WRITE_ONCE(p->svms.faulting_task, current);
+            hmm_range = kzalloc(sizeof(*hmm_range), GFP_KERNEL);

              r = amdgpu_hmm_range_get_pages(&prange->notifier, 
addr, npages,

                                 readonly, owner,
-                               &hmm_range);
+                               hmm_range);
              WRITE_ONCE(p->svms.faulting_task, NULL);
-            if (r)
+            if (r) {
+                kfree(hmm_range);
                  pr_debug("failed %d to get svm range pages\n", r);
+            }
          } else {
              r = -EFAULT;
          }






















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