[PATCH 10/11] drm/amdkfd: Maintain svm_bo reference in page->zone_device_data

[Alex Sierra]

Each zone-device page holds a reference to the SVM BO that manages its
backing storage. This is necessary to correctly hold on to the BO in
case zone_device pages are shared with a child-process.

Signed-off-by: Alex Sierra <alex.sie...@amd.com>
---
 drivers/gpu/drm/amd/amdkfd/kfd_migrate.c | 10 ++++++++--
 drivers/gpu/drm/amd/amdkfd/kfd_svm.c     | 10 +---------
 drivers/gpu/drm/amd/amdkfd/kfd_svm.h     |  9 +++++++++
 3 files changed, 18 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c 
b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
index e9490236c7fa..21b86c35a4f2 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
@@ -245,7 +245,8 @@ svm_migrate_get_vram_page(struct svm_range *prange, 
unsigned long pfn)
        struct page *page;
 
        page = pfn_to_page(pfn);
-       page->zone_device_data = prange;
+       svm_range_bo_ref(prange->svm_bo);
+       page->zone_device_data = prange->svm_bo;
        get_page(page);
        lock_page(page);
 }
@@ -550,7 +551,12 @@ svm_migrate_ram_to_vram(struct svm_range *prange, uint32_t 
best_loc,
 
 static void svm_migrate_page_free(struct page *page)
 {
-       /* Keep this function to avoid warning */
+       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
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c 
b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
index 6572dea2f115..294c9480a184 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
@@ -312,14 +312,6 @@ static bool svm_bo_ref_unless_zero(struct svm_range_bo 
*svm_bo)
        return true;
 }
 
-static struct svm_range_bo *svm_range_bo_ref(struct svm_range_bo *svm_bo)
-{
-       if (svm_bo)
-               kref_get(&svm_bo->kref);
-
-       return svm_bo;
-}
-
 static void svm_range_bo_release(struct kref *kref)
 {
        struct svm_range_bo *svm_bo;
@@ -358,7 +350,7 @@ static void svm_range_bo_release(struct kref *kref)
        kfree(svm_bo);
 }
 
-static void svm_range_bo_unref(struct svm_range_bo *svm_bo)
+void svm_range_bo_unref(struct svm_range_bo *svm_bo)
 {
        if (!svm_bo)
                return;
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.h 
b/drivers/gpu/drm/amd/amdkfd/kfd_svm.h
index 41115a220c2b..3fc1fd8b4fbc 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.h
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.h
@@ -150,6 +150,14 @@ static inline void svm_range_unlock(struct svm_range 
*prange)
        mutex_unlock(&prange->lock);
 }
 
+static inline struct svm_range_bo *svm_range_bo_ref(struct svm_range_bo 
*svm_bo)
+{
+       if (svm_bo)
+               kref_get(&svm_bo->kref);
+
+       return svm_bo;
+}
+
 int svm_range_list_init(struct kfd_process *p);
 void svm_range_list_fini(struct kfd_process *p);
 int svm_ioctl(struct kfd_process *p, enum kfd_ioctl_svm_op op, uint64_t start,
@@ -186,6 +194,7 @@ svm_range_get_pdd_by_adev(struct svm_range *prange, struct 
amdgpu_device *adev);
  */
 #define KFD_IS_SVM_API_SUPPORTED(dev) ((dev)->pgmap.type != 0)
 
+void svm_range_bo_unref(struct svm_range_bo *svm_bo);
 #else
 
 struct kfd_process;
-- 
2.32.0

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