Re: [PATCH 2/2] drm/i915: Support replaying GPU hangs with captured context image

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On Wed, Feb 21, 2024 at 02:22:45PM +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 we 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
> 
> v2:
>  * Fix whitespace alignment as per checkpatch.
>  * Added warning on userspace misuse.
>  * Rebase for extracting ce->default_state shadowing.
> 
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> Cc: Lionel Landwerlin <lionel.g.landwerlin@xxxxxxxxx>
> Cc: Carlos Santa <carlos.santa@xxxxxxxxx>
> Cc: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
> Reviewed-by: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx> # v1

still valid for v2. Thanks for splitting the patch.

> ---
>  drivers/gpu/drm/i915/Kconfig.debug            |  17 +++
>  drivers/gpu/drm/i915/gem/i915_gem_context.c   | 113 ++++++++++++++++++
>  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 |   1 +
>  drivers/gpu/drm/i915/gt/intel_lrc.c           |   3 +-
>  .../gpu/drm/i915/gt/intel_ring_submission.c   |   3 +-
>  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, 193 insertions(+), 3 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..481aacbc1772 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 +2094,95 @@ 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 (drm_WARN_ON_ONCE(&ctx->i915->drm,
> +			     test_bit(CONTEXT_ALLOC_BIT, &ce->flags))) {
> +		/*
> +		 * This is racy but for a debug only API, if userspace is keen
> +		 * to create and configure contexts, while simultaneously using
> +		 * them from a second thread, let them suffer by potentially not
> +		 * executing with the context image they just raced to apply.
> +		 */
> +		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 +2235,10 @@ 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 +2583,7 @@ 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 +2696,22 @@ 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 b179178680a5..d91b33c3664c 100644
> --- a/drivers/gpu/drm/i915/gt/intel_context_types.h
> +++ b/drivers/gpu/drm/i915/gt/intel_context_types.h
> @@ -132,6 +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 d4eb822d20ae..1038659754f8 100644
> --- a/drivers/gpu/drm/i915/gt/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
> @@ -1173,7 +1173,8 @@ int lrc_alloc(struct intel_context *ce, struct intel_engine_cs *engine)
>  
>  	GEM_BUG_ON(ce->state);
>  
> -	ce->default_state = engine->default_state;
> +	if (!intel_context_has_own_state(ce))
> +		ce->default_state = engine->default_state;
>  
>  	vma = __lrc_alloc_state(ce, engine);
>  	if (IS_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 8625e88e785f..72277bc8322e 100644
> --- a/drivers/gpu/drm/i915/gt/intel_ring_submission.c
> +++ b/drivers/gpu/drm/i915/gt/intel_ring_submission.c
> @@ -569,7 +569,8 @@ static int ring_context_alloc(struct intel_context *ce)
>  {
>  	struct intel_engine_cs *engine = ce->engine;
>  
> -	ce->default_state = engine->default_state;
> +	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);
> diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
> index de43048543e8..afd95b2b7e4b 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 2ee338860b7e..e194d17c3568 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
> 



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