[PATCH v2 2/6] drm/amdgpu: move devcoredump generation to a worker

[Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>]

Update the way drm_coredump_printer is used based on its documentation
and Xe's code: the main idea is to generate the final version in one go
and then use memcpy to return the chunks requested by the caller of
amdgpu_devcoredump_read.

The generation is moved to a separate worker thread.

This cuts the time to copy the dump from 40s to ~0s on my machine.

Signed-off-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu.h           |  5 ++
 .../gpu/drm/amd/amdgpu/amdgpu_dev_coredump.c  | 66 +++++++++++++++++--
 .../gpu/drm/amd/amdgpu/amdgpu_dev_coredump.h  |  9 +++
 3 files changed, 74 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
index 057c8bd2ad89..ae81a428cfb5 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -1200,6 +1200,11 @@ struct amdgpu_device {
 
 	struct amdgpu_reset_domain	*reset_domain;
 
+#ifdef CONFIG_DEV_COREDUMP
+	/* If a coredump state capture is in progress don't start a new one. */
+	bool coredump_in_progress;
+#endif
+
 	struct mutex			benchmark_mutex;
 
 	bool                            scpm_enabled;
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_dev_coredump.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_dev_coredump.c
index 42a969512dcc..0808ca98ccd9 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_dev_coredump.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_dev_coredump.c
@@ -34,6 +34,8 @@ void amdgpu_coredump(struct amdgpu_device *adev, bool skip_vram_check,
 }
 #else
 
+#define AMDGPU_CORE_DUMP_SIZE_MAX (256 * 1024 * 1024)
+
 const char *hw_ip_names[MAX_HWIP] = {
 	[GC_HWIP]		= "GC",
 	[HDP_HWIP]		= "HDP",
@@ -196,11 +198,9 @@ static void amdgpu_devcoredump_fw_info(struct amdgpu_device *adev,
 }
 
 static ssize_t
-amdgpu_devcoredump_read(char *buffer, loff_t offset, size_t count,
-			void *data, size_t datalen)
+amdgpu_devcoredump_format(char *buffer, size_t count, struct amdgpu_coredump_info *coredump)
 {
 	struct drm_printer p;
-	struct amdgpu_coredump_info *coredump = data;
 	struct drm_print_iterator iter;
 	struct amdgpu_vm_fault_info *fault_info;
 	struct amdgpu_ip_block *ip_block;
@@ -208,7 +208,6 @@ amdgpu_devcoredump_read(char *buffer, loff_t offset, size_t count,
 
 	iter.data = buffer;
 	iter.offset = 0;
-	iter.start = offset;
 	iter.remain = count;
 
 	p = drm_coredump_printer(&iter);
@@ -323,11 +322,60 @@ amdgpu_devcoredump_read(char *buffer, loff_t offset, size_t count,
 	return count - iter.remain;
 }
 
+static ssize_t
+amdgpu_devcoredump_read(char *buffer, loff_t offset, size_t count,
+			void *data, size_t datalen)
+{
+	struct amdgpu_coredump_info *coredump = data;
+	ssize_t byte_copied;
+
+	if (!coredump)
+		return -ENODEV;
+
+	flush_work(&coredump->work);
+
+	if (!coredump->formatted)
+		return -ENODEV;
+
+	if (offset >= coredump->formatted_size)
+		return 0;
+
+	byte_copied = count < coredump->formatted_size - offset ? count :
+		coredump->formatted_size - offset;
+	memcpy(buffer, coredump->formatted + offset, byte_copied);
+
+	return byte_copied;
+}
+
 static void amdgpu_devcoredump_free(void *data)
 {
+	struct amdgpu_coredump_info *coredump = data;
+
+	cancel_work_sync(&coredump->work);
+	coredump->adev->coredump_in_progress = false;
+	kfree(coredump->formatted);
 	kfree(data);
 }
 
+static void amdgpu_devcoredump_deferred_work(struct work_struct *work)
+{
+	struct amdgpu_coredump_info *coredump = container_of(work, typeof(*coredump), work);
+
+	dev_coredumpm(coredump->adev->dev, THIS_MODULE, coredump, 0, GFP_NOWAIT,
+		      amdgpu_devcoredump_read, amdgpu_devcoredump_free);
+
+	/* Do a one-time preparation of the coredump output because
+	 * repeatingly calling drm_coredump_printer is very slow.
+	 */
+	coredump->formatted_size =
+		amdgpu_devcoredump_format(NULL, AMDGPU_CORE_DUMP_SIZE_MAX, coredump);
+	coredump->formatted = kvzalloc(coredump->formatted_size, GFP_KERNEL);
+	if (!coredump->formatted)
+		return;
+	amdgpu_devcoredump_format(coredump->formatted, coredump->formatted_size, coredump);
+	coredump->adev->coredump_in_progress = false;
+}
+
 void amdgpu_coredump(struct amdgpu_device *adev, bool skip_vram_check,
 		     bool vram_lost, struct amdgpu_job *job)
 {
@@ -335,10 +383,15 @@ void amdgpu_coredump(struct amdgpu_device *adev, bool skip_vram_check,
 	struct amdgpu_coredump_info *coredump;
 	struct drm_sched_job *s_job;
 
+	if (adev->coredump_in_progress)
+		return;
+
 	coredump = kzalloc(sizeof(*coredump), GFP_NOWAIT);
 	if (!coredump)
 		return;
 
+	adev->coredump_in_progress = true;
+
 	coredump->skip_vram_check = skip_vram_check;
 	coredump->reset_vram_lost = vram_lost;
 
@@ -361,8 +414,9 @@ void amdgpu_coredump(struct amdgpu_device *adev, bool skip_vram_check,
 
 	ktime_get_ts64(&coredump->reset_time);
 
-	dev_coredumpm(dev->dev, THIS_MODULE, coredump, 0, GFP_NOWAIT,
-		      amdgpu_devcoredump_read, amdgpu_devcoredump_free);
+	/* Kick off coredump formatting to a worker thread. */
+	INIT_WORK(&coredump->work, amdgpu_devcoredump_deferred_work);
+	queue_work(system_unbound_wq, &coredump->work);
 
 	drm_info(dev, "AMDGPU device coredump file has been created\n");
 	drm_info(dev, "Check your /sys/class/drm/card%d/device/devcoredump/data\n",
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_dev_coredump.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_dev_coredump.h
index ef9772c6bcc9..4c37a852b74a 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_dev_coredump.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_dev_coredump.h
@@ -35,9 +35,18 @@ struct amdgpu_coredump_info {
 	struct amdgpu_device            *adev;
 	struct amdgpu_task_info         reset_task_info;
 	struct timespec64               reset_time;
+
+	struct work_struct work;
+
 	bool                            skip_vram_check;
 	bool                            reset_vram_lost;
 	struct amdgpu_ring              *ring;
+	/* Readable form of coredevdump, generate once to speed up
+	 * reading it (see drm_coredump_printer's documentation).
+	 */
+	ssize_t				formatted_size;
+	char				*formatted;
+
 };
 #endif
 
-- 
2.43.0