Re: [PATCH] drm/i915: Fix a lockdep warning at error capture

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Commit message and code changes look good to me.

Reviewed-by: Gwan-gyeong Mun <gwan-gyeong.mun@xxxxxxxxx>

This is a question about the issue mentioned in this patch, not the patch. The tests (igt@gem_ctx_persistence@legacy-engines-hostile@render) mentioned in this issue ( https://gitlab.freedesktop.org/drm/intel/-/issues/5595 ) are dealing with a test that causes gpu reset / hang? Or did the reset happen during the test?

br,
G.G.

On 6/17/22 4:21 PM, Das, Nirmoy wrote:
Missed the fdo issue ref:

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/5595

On 6/17/2022 1:55 PM, Nirmoy Das wrote:
For some platfroms we use stop_machine version of
gen8_ggtt_insert_page/gen8_ggtt_insert_entries to avoid a
concurrent GGTT access bug but this causes a circular locking
dependency warning:

   Possible unsafe locking scenario:
         CPU0                    CPU1
         ----                    ----
    lock(&ggtt->error_mutex);
                                 lock(dma_fence_map);
                                 lock(&ggtt->error_mutex);
    lock(cpu_hotplug_lock);

Fix this by calling gen8_ggtt_insert_page/gen8_ggtt_insert_entries
directly at error capture which is concurrent GGTT access safe because
reset path make sure of that.

Suggested-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Nirmoy Das <nirmoy.das@xxxxxxxxx>
---
  drivers/gpu/drm/i915/gt/intel_gt_gmch.c  | 2 ++
  drivers/gpu/drm/i915/gt/intel_gtt.h      | 9 +++++++++
  drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c | 5 ++++-
  drivers/gpu/drm/i915/i915_gpu_error.c    | 8 ++++++--
  4 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_gt_gmch.c b/drivers/gpu/drm/i915/gt/intel_gt_gmch.c
index 18e488672d1b..2260ed576776 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt_gmch.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt_gmch.c
@@ -629,6 +629,8 @@ int intel_gt_gmch_gen8_probe(struct i915_ggtt *ggtt)
      if (intel_vm_no_concurrent_access_wa(i915)) {
          ggtt->vm.insert_entries = bxt_vtd_ggtt_insert_entries__BKL;
          ggtt->vm.insert_page    = bxt_vtd_ggtt_insert_page__BKL;
+        ggtt->vm.raw_insert_page = gen8_ggtt_insert_page;
+        ggtt->vm.raw_insert_entries = gen8_ggtt_insert_entries;
          ggtt->vm.bind_async_flags =
              I915_VMA_GLOBAL_BIND | I915_VMA_LOCAL_BIND;
      }
diff --git a/drivers/gpu/drm/i915/gt/intel_gtt.h b/drivers/gpu/drm/i915/gt/intel_gtt.h
index a40d928b3888..f9a1f3d17272 100644
--- a/drivers/gpu/drm/i915/gt/intel_gtt.h
+++ b/drivers/gpu/drm/i915/gt/intel_gtt.h
@@ -306,6 +306,15 @@ struct i915_address_space {
                     struct i915_vma_resource *vma_res,
                     enum i915_cache_level cache_level,
                     u32 flags);
+    void (*raw_insert_page)(struct i915_address_space *vm,
+                dma_addr_t addr,
+                u64 offset,
+                enum i915_cache_level cache_level,
+                u32 flags);
+    void (*raw_insert_entries)(struct i915_address_space *vm,
+                   struct i915_vma_resource *vma_res,
+                   enum i915_cache_level cache_level,
+                   u32 flags);
      void (*cleanup)(struct i915_address_space *vm);
      void (*foreach)(struct i915_address_space *vm,
diff --git a/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c b/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c
index d2c5c9367cc4..c06e83872c34 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c
@@ -493,7 +493,10 @@ static void uc_fw_bind_ggtt(struct intel_uc_fw *uc_fw)
      if (i915_gem_object_is_lmem(obj))
          pte_flags |= PTE_LM;
-    ggtt->vm.insert_entries(&ggtt->vm, dummy, I915_CACHE_NONE, pte_flags);
+    if (ggtt->vm.raw_insert_entries)
+        ggtt->vm.raw_insert_entries(&ggtt->vm, dummy, I915_CACHE_NONE, pte_flags);
+    else
+        ggtt->vm.insert_entries(&ggtt->vm, dummy, I915_CACHE_NONE, pte_flags);
  }
  static void uc_fw_unbind_ggtt(struct intel_uc_fw *uc_fw)
diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
index bff8a111424a..f9b1969ed7ed 100644
--- a/drivers/gpu/drm/i915/i915_gpu_error.c
+++ b/drivers/gpu/drm/i915/i915_gpu_error.c
@@ -1104,8 +1104,12 @@ i915_vma_coredump_create(const struct intel_gt *gt,
          for_each_sgt_daddr(dma, iter, vma_res->bi.pages) {
              mutex_lock(&ggtt->error_mutex);
-            ggtt->vm.insert_page(&ggtt->vm, dma, slot,
-                         I915_CACHE_NONE, 0);
+            if (ggtt->vm.raw_insert_page)
+                ggtt->vm.raw_insert_page(&ggtt->vm, dma, slot,
+                             I915_CACHE_NONE, 0);
+            else
+                ggtt->vm.insert_page(&ggtt->vm, dma, slot,
+                             I915_CACHE_NONE, 0);
              mb();
              s = io_mapping_map_wc(&ggtt->iomap, slot, PAGE_SIZE);



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