Re: [RFC] drm/i915: Support replaying GPU hangs with captured context image

Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx> · Wed, 21 Feb 2024 08:24:08 +0000

On 20/02/2024 22:50, Rodrigo Vivi wrote:
On Tue, Feb 13, 2024 at 01:14:34PM +0000, Tvrtko Ursulin wrote:
From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>

When debugging GPU hangs Mesa developers are finding it useful to replay
the captured error state against the simulator. But due various simulator
limitations which prevent replicating all hangs, one step further is being
able to replay against a real GPU.

This is almost doable today with the missing part being able to upload the
captured context image into the driver state prior to executing the
uploaded hanging batch and all the buffers.

To enable this last part we add a new context parameter called
I915_CONTEXT_PARAM_CONTEXT_IMAGE. It follows the existing SSEU
configuration pattern of being able to select which context to apply
against, paired with the actual image and its size.

Since this is adding a new concept of debug only uapi, we hide it behind
a new kconfig option and also require activation with a module parameter.
Together with a warning banner printed at driver load, all those combined
should be sufficient to guard against inadvertently enabling the feature.

In terms of implementation the only trivial change is shadowing of the
default state from engine to context. We also allow the legacy context
set param to be used since that removes the need to record the per context
data in the proto context, while still allowing flexibility of specifying
context images for any context.

Mesa MR using the uapi can be seen at:
   https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27594

I just wonder if it would be better to split the default_state in a separate
patch.... but from what I could see it looks correct.

It definitely makes sense to split it. I was just a bit lazy while 
testing the waters. After all this is a very novel idea of debug only 
uapi outside debugfs so I wasn't too sure how it will be received. Stay 
tuned for v2.

Regards,

Tvrtko


Also, I have to say that this approach is nice, clean and well protected.
And much simpler then I imagined when I saw the idea around.

Feel free to use:
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>


Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Cc: Lionel Landwerlin <lionel.g.landwerlin@xxxxxxxxx>
Cc: Carlos Santa <carlos.santa@xxxxxxxxx>
---
  drivers/gpu/drm/i915/Kconfig.debug            |  17 +++
  drivers/gpu/drm/i915/gem/i915_gem_context.c   | 106 ++++++++++++++++++
  drivers/gpu/drm/i915/gt/intel_context.c       |   2 +
  drivers/gpu/drm/i915/gt/intel_context.h       |  22 ++++
  drivers/gpu/drm/i915/gt/intel_context_types.h |   3 +
  drivers/gpu/drm/i915/gt/intel_lrc.c           |   8 +-
  .../gpu/drm/i915/gt/intel_ring_submission.c   |   8 +-
  drivers/gpu/drm/i915/i915_params.c            |   5 +
  drivers/gpu/drm/i915/i915_params.h            |   3 +-
  include/uapi/drm/i915_drm.h                   |  27 +++++
  10 files changed, 194 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/Kconfig.debug b/drivers/gpu/drm/i915/Kconfig.debug
index 5b7162076850..32e9f70e91ed 100644
--- a/drivers/gpu/drm/i915/Kconfig.debug
+++ b/drivers/gpu/drm/i915/Kconfig.debug
@@ -16,6 +16,23 @@ config DRM_I915_WERROR
  
  	  If in doubt, say "N".
  
+config DRM_I915_REPLAY_GPU_HANGS_API
+	bool "Enable GPU hang replay userspace API"
+	depends on DRM_I915
+	depends on EXPERT
+	default n
+	help
+	  Choose this option if you want to enable special and unstable
+	  userspace API used for replaying GPU hangs on a running system.
+
+	  This API is intended to be used by userspace graphics stack developers
+	  and provides no stability guarantees.
+
+	  The API needs to be activated at boot time using the
+	  enable_debug_only_api module parameter.
+
+	  If in doubt, say "N".
+
  config DRM_I915_DEBUG
  	bool "Enable additional driver debugging"
  	depends on DRM_I915
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
index dcbfe32fd30c..1cfd624bd978 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
@@ -78,6 +78,7 @@
  #include "gt/intel_engine_user.h"
  #include "gt/intel_gpu_commands.h"
  #include "gt/intel_ring.h"
+#include "gt/shmem_utils.h"
  
  #include "pxp/intel_pxp.h"
  
@@ -949,6 +950,7 @@ static int set_proto_ctx_param(struct drm_i915_file_private *fpriv,
  	case I915_CONTEXT_PARAM_NO_ZEROMAP:
  	case I915_CONTEXT_PARAM_BAN_PERIOD:
  	case I915_CONTEXT_PARAM_RINGSIZE:
+	case I915_CONTEXT_PARAM_CONTEXT_IMAGE:
  	default:
  		ret = -EINVAL;
  		break;
@@ -2092,6 +2094,88 @@ static int get_protected(struct i915_gem_context *ctx,
  	return 0;
  }
  
+static int set_context_image(struct i915_gem_context *ctx,
+			     struct drm_i915_gem_context_param *args)
+{
+	struct i915_gem_context_param_context_image user;
+	struct intel_context *ce;
+	struct file *shmem_state;
+	unsigned long lookup;
+	void *state;
+	int ret = 0;
+
+	if (!IS_ENABLED(CONFIG_DRM_I915_REPLAY_GPU_HANGS_API))
+		return -EINVAL;
+
+	if (!ctx->i915->params.enable_debug_only_api)
+		return -EINVAL;
+
+	if (args->size < sizeof(user))
+		return -EINVAL;
+
+	if (copy_from_user(&user, u64_to_user_ptr(args->value), sizeof(user)))
+		return -EFAULT;
+
+	if (user.mbz)
+		return -EINVAL;
+
+	if (user.flags & ~(I915_CONTEXT_IMAGE_FLAG_ENGINE_INDEX))
+		return -EINVAL;
+
+	lookup = 0;
+	if (user.flags & I915_CONTEXT_IMAGE_FLAG_ENGINE_INDEX)
+		lookup |= LOOKUP_USER_INDEX;
+
+	ce = lookup_user_engine(ctx, lookup, &user.engine);
+	if (IS_ERR(ce))
+		return PTR_ERR(ce);
+
+	if (user.size < ce->engine->context_size) {
+		ret = -EINVAL;
+		goto out_ce;
+	}
+
+	if (test_bit(CONTEXT_ALLOC_BIT, &ce->flags)) {
+		ret = -EBUSY;
+		goto out_ce;
+	}
+
+	state = kmalloc(ce->engine->context_size, GFP_KERNEL);
+	if (!state) {
+		ret = -ENOMEM;
+		goto out_ce;
+	}
+
+	if (copy_from_user(state, u64_to_user_ptr(user.image),
+			   ce->engine->context_size)) {
+		ret = -EFAULT;
+		goto out_state;
+	}
+
+	shmem_state = shmem_create_from_data(ce->engine->name,
+					     state, ce->engine->context_size);
+	if (IS_ERR(shmem_state)) {
+		ret = PTR_ERR(shmem_state);
+		goto out_state;
+	}
+
+	if (intel_context_set_own_state(ce)) {
+		ret = -EBUSY;
+		fput(shmem_state);
+		goto out_state;
+	}
+
+	ce->default_state = shmem_state;
+
+	args->size = sizeof(user);
+
+out_state:
+	kfree(state);
+out_ce:
+	intel_context_put(ce);
+	return ret;
+}
+
  static int ctx_setparam(struct drm_i915_file_private *fpriv,
  			struct i915_gem_context *ctx,
  			struct drm_i915_gem_context_param *args)
@@ -2144,6 +2228,10 @@ static int ctx_setparam(struct drm_i915_file_private *fpriv,
  		ret = set_persistence(ctx, args);
  		break;
  
+	case I915_CONTEXT_PARAM_CONTEXT_IMAGE:
+		ret = set_context_image(ctx, args);
+		break;
+
  	case I915_CONTEXT_PARAM_PROTECTED_CONTENT:
  	case I915_CONTEXT_PARAM_NO_ZEROMAP:
  	case I915_CONTEXT_PARAM_BAN_PERIOD:
@@ -2488,6 +2576,7 @@ int i915_gem_context_getparam_ioctl(struct drm_device *dev, void *data,
  	case I915_CONTEXT_PARAM_BAN_PERIOD:
  	case I915_CONTEXT_PARAM_ENGINES:
  	case I915_CONTEXT_PARAM_RINGSIZE:
+	case I915_CONTEXT_PARAM_CONTEXT_IMAGE:
  	default:
  		ret = -EINVAL;
  		break;
@@ -2600,5 +2689,22 @@ int __init i915_gem_context_module_init(void)
  	if (!slab_luts)
  		return -ENOMEM;
  
+	if (IS_ENABLED(CONFIG_DRM_I915_REPLAY_GPU_HANGS_API)) {
+		pr_notice("**************************************************************\n");
+		pr_notice("**     NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE     **\n");
+		pr_notice("**                                                          **\n");
+		if (i915_modparams.enable_debug_only_api)
+			pr_notice("** i915.enable_debug_only_api is intended to be set         **\n");
+		else
+			pr_notice("** CONFIG_DRM_I915_REPLAY_GPU_HANGS_API builds are intended **\n");
+		pr_notice("** for specific userspace graphics stack developers only!   **\n");
+		pr_notice("**                                                          **\n");
+		pr_notice("** If you are seeing this message please report this to the **\n");
+		pr_notice("** provider of your kernel build.                           **\n");
+		pr_notice("**                                                          **\n");
+		pr_notice("**     NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE     **\n");
+		pr_notice("**************************************************************\n");
+	}
+
  	return 0;
  }
diff --git a/drivers/gpu/drm/i915/gt/intel_context.c b/drivers/gpu/drm/i915/gt/intel_context.c
index a2f1245741bb..b1b8695ba7c9 100644
--- a/drivers/gpu/drm/i915/gt/intel_context.c
+++ b/drivers/gpu/drm/i915/gt/intel_context.c
@@ -27,6 +27,8 @@ static void rcu_context_free(struct rcu_head *rcu)
  	struct intel_context *ce = container_of(rcu, typeof(*ce), rcu);
  
  	trace_intel_context_free(ce);
+	if (intel_context_has_own_state(ce))
+		fput(ce->default_state);
  	kmem_cache_free(slab_ce, ce);
  }
  
diff --git a/drivers/gpu/drm/i915/gt/intel_context.h b/drivers/gpu/drm/i915/gt/intel_context.h
index 25564c01507e..9f523999acd1 100644
--- a/drivers/gpu/drm/i915/gt/intel_context.h
+++ b/drivers/gpu/drm/i915/gt/intel_context.h
@@ -375,6 +375,28 @@ intel_context_clear_nopreempt(struct intel_context *ce)
  	clear_bit(CONTEXT_NOPREEMPT, &ce->flags);
  }
  
+#if IS_ENABLED(CONFIG_DRM_I915_REPLAY_GPU_HANGS_API)
+static inline bool intel_context_has_own_state(const struct intel_context *ce)
+{
+	return test_bit(CONTEXT_OWN_STATE, &ce->flags);
+}
+
+static inline bool intel_context_set_own_state(struct intel_context *ce)
+{
+	return test_and_set_bit(CONTEXT_OWN_STATE, &ce->flags);
+}
+#else
+static inline bool intel_context_has_own_state(const struct intel_context *ce)
+{
+	return false;
+}
+
+static inline bool intel_context_set_own_state(struct intel_context *ce)
+{
+	return true;
+}
+#endif
+
  u64 intel_context_get_total_runtime_ns(struct intel_context *ce);
  u64 intel_context_get_avg_runtime_ns(struct intel_context *ce);
  
diff --git a/drivers/gpu/drm/i915/gt/intel_context_types.h b/drivers/gpu/drm/i915/gt/intel_context_types.h
index 7eccbd70d89f..b2ea14155ff0 100644
--- a/drivers/gpu/drm/i915/gt/intel_context_types.h
+++ b/drivers/gpu/drm/i915/gt/intel_context_types.h
@@ -87,6 +87,8 @@ struct intel_context {
  		struct rcu_head rcu;
  	};
  
+	struct file *default_state;
+
  	struct intel_engine_cs *engine;
  	struct intel_engine_cs *inflight;
  #define __intel_context_inflight(engine) ptr_mask_bits(engine, 3)
@@ -130,6 +132,7 @@ struct intel_context {
  #define CONTEXT_PERMA_PIN		11
  #define CONTEXT_IS_PARKING		12
  #define CONTEXT_EXITING			13
+#define CONTEXT_OWN_STATE		14
  
  	struct {
  		u64 timeout_us;
diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
index 7c367ba8d9dc..1038659754f8 100644
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -1060,9 +1060,8 @@ void lrc_init_state(struct intel_context *ce,
  
  	set_redzone(state, engine);
  
-	if (engine->default_state) {
-		shmem_read(engine->default_state, 0,
-			   state, engine->context_size);
+	if (ce->default_state) {
+		shmem_read(ce->default_state, 0, state, engine->context_size);
  		__set_bit(CONTEXT_VALID_BIT, &ce->flags);
  		inhibit = false;
  	}
@@ -1174,6 +1173,9 @@ int lrc_alloc(struct intel_context *ce, struct intel_engine_cs *engine)
  
  	GEM_BUG_ON(ce->state);
  
+	if (!intel_context_has_own_state(ce))
+		ce->default_state = engine->default_state;
+
  	vma = __lrc_alloc_state(ce, engine);
  	if (IS_ERR(vma))
  		return PTR_ERR(vma);
diff --git a/drivers/gpu/drm/i915/gt/intel_ring_submission.c b/drivers/gpu/drm/i915/gt/intel_ring_submission.c
index 92085ffd23de..72277bc8322e 100644
--- a/drivers/gpu/drm/i915/gt/intel_ring_submission.c
+++ b/drivers/gpu/drm/i915/gt/intel_ring_submission.c
@@ -474,8 +474,7 @@ static int ring_context_init_default_state(struct intel_context *ce,
  	if (IS_ERR(vaddr))
  		return PTR_ERR(vaddr);
  
-	shmem_read(ce->engine->default_state, 0,
-		   vaddr, ce->engine->context_size);
+	shmem_read(ce->default_state, 0, vaddr, ce->engine->context_size);
  
  	i915_gem_object_flush_map(obj);
  	__i915_gem_object_release_map(obj);
@@ -491,7 +490,7 @@ static int ring_context_pre_pin(struct intel_context *ce,
  	struct i915_address_space *vm;
  	int err = 0;
  
-	if (ce->engine->default_state &&
+	if (ce->default_state &&
  	    !test_bit(CONTEXT_VALID_BIT, &ce->flags)) {
  		err = ring_context_init_default_state(ce, ww);
  		if (err)
@@ -570,6 +569,9 @@ static int ring_context_alloc(struct intel_context *ce)
  {
  	struct intel_engine_cs *engine = ce->engine;
  
+	if (!intel_context_has_own_state(ce))
+		ce->default_state = engine->default_state;
+
  	/* One ringbuffer to rule them all */
  	GEM_BUG_ON(!engine->legacy.ring);
  	ce->ring = engine->legacy.ring;
diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
index de43048543e8..1226af5fd96f 100644
--- a/drivers/gpu/drm/i915/i915_params.c
+++ b/drivers/gpu/drm/i915/i915_params.c
@@ -134,6 +134,11 @@ i915_param_named_unsafe(lmem_size, uint, 0400,
  i915_param_named_unsafe(lmem_bar_size, uint, 0400,
  			"Set the lmem bar size(in MiB).");
  
+#if IS_ENABLED(CONFIG_DRM_I915_REPLAY_GPU_HANGS_API)
+i915_param_named(enable_debug_only_api, bool, 0400,
+	"Enable support for unstable debug only userspace API. (default:false)");
+#endif
+
  static void _param_print_bool(struct drm_printer *p, const char *name,
  			      bool val)
  {
diff --git a/drivers/gpu/drm/i915/i915_params.h b/drivers/gpu/drm/i915/i915_params.h
index 1315d7fac850..e2cdf12ce611 100644
--- a/drivers/gpu/drm/i915/i915_params.h
+++ b/drivers/gpu/drm/i915/i915_params.h
@@ -64,7 +64,8 @@ struct drm_printer;
  	/* leave bools at the end to not create holes */ \
  	param(bool, enable_hangcheck, true, 0600) \
  	param(bool, error_capture, true, IS_ENABLED(CONFIG_DRM_I915_CAPTURE_ERROR) ? 0600 : 0) \
-	param(bool, enable_gvt, false, IS_ENABLED(CONFIG_DRM_I915_GVT) ? 0400 : 0)
+	param(bool, enable_gvt, false, IS_ENABLED(CONFIG_DRM_I915_GVT) ? 0400 : 0) \
+	param(bool, enable_debug_only_api, false, IS_ENABLED(CONFIG_DRM_I915_REPLAY_GPU_HANGS_API) ? 0400 : 0)
  
  #define MEMBER(T, member, ...) T member;
  struct i915_params {
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index fd4f9574d177..0af932e61d12 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -2154,6 +2154,15 @@ struct drm_i915_gem_context_param {
  	__u64 value;
  };
  
+/*
+ * I915_CONTEXT_PARAM_CONTEXT_IMAGE:
+ *
+ * Allows userspace to provide own context images.
+ *
+ * Note that this is a debug API not available on production kernel builds.
+ */
+#define I915_CONTEXT_PARAM_CONTEXT_IMAGE	0xe
+
  /*
   * Context SSEU programming
   *
@@ -2549,6 +2558,24 @@ struct i915_context_param_engines {
  	struct i915_engine_class_instance engines[N__]; \
  } __attribute__((packed)) name__
  
+struct i915_gem_context_param_context_image {
+	/** @engine: Engine class & instance to be configured. */
+	struct i915_engine_class_instance engine;
+
+	/** @flags: One of the supported flags or zero. */
+	__u32 flags;
+#define I915_CONTEXT_IMAGE_FLAG_ENGINE_INDEX (1u << 0)
+
+	/** @size: Size of the image blob pointed to by @image. */
+	__u32 size;
+
+	/** @mbz: Must be zero. */
+	__u32 mbz;
+
+	/** @image: Userspace memory containing the context image. */
+	__u64 image;
+} __attribute__((packed));
+
  /**
   * struct drm_i915_gem_context_create_ext_setparam - Context parameter
   * to set or query during context creation.
--
2.40.1







