[Intel-gfx] [PATCH v2] drm/i915: Fix a lockdep warning at error capture

[Nirmoy Das]

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.

v2: Fix rebase conflict and added a comment.

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/5595
Reviewed-by: Gwan-gyeong Mun <gwan-gyeong.mun at intel.com>
Suggested-by: Chris Wilson <chris at chris-wilson.co.uk>
Signed-off-by: Nirmoy Das <nirmoy.das at intel.com>
---
 drivers/gpu/drm/i915/gt/intel_ggtt.c     | 10 ++++++++++
 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, 29 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_ggtt.c b/drivers/gpu/drm/i915/gt/intel_ggtt.c
index ffff96180313..15a915bb4088 100644
--- a/drivers/gpu/drm/i915/gt/intel_ggtt.c
+++ b/drivers/gpu/drm/i915/gt/intel_ggtt.c
@@ -960,6 +960,16 @@ static int gen8_gmch_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;
+
+		/*
+		 * Calling stop_machine() version of GGTT update function
+		 * at error capture/reset path will raise lockdep warning.
+		 * Allow calling gen8_ggtt_insert_* directly at reset path
+		 * which is safe from parallel GGTT updates.
+		 */
+		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 29fd3a9e8b2e..e639434e97fd 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);
-- 
2.35.1