Re: [Intel-gfx] [PATCH 16/21] drm/i915/gem: Delay context creation

[Daniel Vetter <daniel@ffwll.ch>]

Yeah this needs some text to explain what/why you're doing this, and maybe
some rough sketch of the locking design.

On Fri, Apr 23, 2021 at 05:31:26PM -0500, Jason Ekstrand wrote:
> Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>
> ---
>  drivers/gpu/drm/i915/gem/i915_gem_context.c   | 657 ++++++++++++++++--
>  drivers/gpu/drm/i915/gem/i915_gem_context.h   |   3 +
>  .../gpu/drm/i915/gem/i915_gem_context_types.h |  26 +
>  .../gpu/drm/i915/gem/selftests/mock_context.c |   5 +-
>  drivers/gpu/drm/i915/i915_drv.h               |  17 +-
>  5 files changed, 648 insertions(+), 60 deletions(-)

So I think the patch split here is a bit unfortunate, because you're
adding the new vm/engine validation code for proto context here, but the
old stuff is only removed in the next patches that make vm/engines
immutable after first use.

I think a better split would be if this patch here only has all the
scaffolding. You already have the EOPNOTSUPP fallback (which I hope gets
removed), so moving the conversion entirely to later patches should be all
fine.

Or do I miss something?

I think the only concern I'm seeing is that bisectability might be a bit
lost, because we finalize the context in some cases in setparam. And if we
do the conversion in a different order than the one media uses for its
setparam, then later setparam might fail because the context is finalized
already. But also
- it's just bisectability of media functionality I think
- just check which order media calls CTX_SETPARAM and use that to do the
  conversion

And we should be fine ... I think?

Some more thoughts below, but the proto ctx stuff itself looks fine.

> 
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> index db9153e0f85a7..aa8e61211924f 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> @@ -193,8 +193,15 @@ static int validate_priority(struct drm_i915_private *i915,
>  
>  static void proto_context_close(struct i915_gem_proto_context *pc)
>  {
> +	int i;
> +
>  	if (pc->vm)
>  		i915_vm_put(pc->vm);
> +	if (pc->user_engines) {
> +		for (i = 0; i < pc->num_user_engines; i++)
> +			kfree(pc->user_engines[i].siblings);
> +		kfree(pc->user_engines);
> +	}
>  	kfree(pc);
>  }
>  
> @@ -274,12 +281,417 @@ proto_context_create(struct drm_i915_private *i915, unsigned int flags)
>  	proto_context_set_persistence(i915, pc, true);
>  	pc->sched.priority = I915_PRIORITY_NORMAL;
>  
> +	pc->num_user_engines = -1;
> +	pc->user_engines = NULL;
> +
>  	if (flags & I915_CONTEXT_CREATE_FLAGS_SINGLE_TIMELINE)
>  		pc->single_timeline = true;
>  
>  	return pc;
>  }
>  
> +static int proto_context_register_locked(struct drm_i915_file_private *fpriv,
> +					 struct i915_gem_proto_context *pc,
> +					 u32 *id)
> +{
> +	int ret;
> +	void *old;

assert_lock_held just for consistency.

> +
> +	ret = xa_alloc(&fpriv->context_xa, id, NULL, xa_limit_32b, GFP_KERNEL);
> +	if (ret)
> +		return ret;
> +
> +	old = xa_store(&fpriv->proto_context_xa, *id, pc, GFP_KERNEL);
> +	if (xa_is_err(old)) {
> +		xa_erase(&fpriv->context_xa, *id);
> +		return xa_err(old);
> +	}
> +	GEM_BUG_ON(old);
> +
> +	return 0;
> +}
> +
> +static int proto_context_register(struct drm_i915_file_private *fpriv,
> +				  struct i915_gem_proto_context *pc,
> +				  u32 *id)
> +{
> +	int ret;
> +
> +	mutex_lock(&fpriv->proto_context_lock);
> +	ret = proto_context_register_locked(fpriv, pc, id);
> +	mutex_unlock(&fpriv->proto_context_lock);
> +
> +	return ret;
> +}
> +
> +static int set_proto_ctx_vm(struct drm_i915_file_private *fpriv,
> +			    struct i915_gem_proto_context *pc,
> +			    const struct drm_i915_gem_context_param *args)
> +{
> +	struct i915_address_space *vm;
> +
> +	if (args->size)
> +		return -EINVAL;
> +
> +	if (!pc->vm)
> +		return -ENODEV;
> +
> +	if (upper_32_bits(args->value))
> +		return -ENOENT;
> +
> +	rcu_read_lock();
> +	vm = xa_load(&fpriv->vm_xa, args->value);
> +	if (vm && !kref_get_unless_zero(&vm->ref))
> +		vm = NULL;
> +	rcu_read_unlock();
> +	if (!vm)
> +		return -ENOENT;
> +
> +	i915_vm_put(pc->vm);
> +	pc->vm = vm;
> +
> +	return 0;
> +}
> +
> +struct set_proto_ctx_engines {
> +	struct drm_i915_private *i915;
> +	unsigned num_engines;
> +	struct i915_gem_proto_engine *engines;
> +};
> +
> +static int
> +set_proto_ctx_engines_balance(struct i915_user_extension __user *base,
> +			      void *data)
> +{
> +	struct i915_context_engines_load_balance __user *ext =
> +		container_of_user(base, typeof(*ext), base);
> +	const struct set_proto_ctx_engines *set = data;
> +	struct drm_i915_private *i915 = set->i915;
> +	struct intel_engine_cs **siblings;
> +	u16 num_siblings, idx;
> +	unsigned int n;
> +	int err;
> +
> +	if (!HAS_EXECLISTS(i915))
> +		return -ENODEV;
> +
> +	if (intel_uc_uses_guc_submission(&i915->gt.uc))
> +		return -ENODEV; /* not implement yet */
> +
> +	if (get_user(idx, &ext->engine_index))
> +		return -EFAULT;
> +
> +	if (idx >= set->num_engines) {
> +		drm_dbg(&i915->drm, "Invalid placement value, %d >= %d\n",
> +			idx, set->num_engines);
> +		return -EINVAL;
> +	}
> +
> +	idx = array_index_nospec(idx, set->num_engines);
> +	if (set->engines[idx].type != I915_GEM_ENGINE_TYPE_INVALID) {
> +		drm_dbg(&i915->drm,
> +			"Invalid placement[%d], already occupied\n", idx);
> +		return -EEXIST;
> +	}
> +
> +	if (get_user(num_siblings, &ext->num_siblings))
> +		return -EFAULT;
> +
> +	err = check_user_mbz(&ext->flags);
> +	if (err)
> +		return err;
> +
> +	err = check_user_mbz(&ext->mbz64);
> +	if (err)
> +		return err;
> +
> +	if (num_siblings == 0)
> +		return 0;
> +
> +	siblings = kmalloc_array(num_siblings, sizeof(*siblings), GFP_KERNEL);
> +	if (!siblings)
> +		return -ENOMEM;
> +
> +	for (n = 0; n < num_siblings; n++) {
> +		struct i915_engine_class_instance ci;
> +
> +		if (copy_from_user(&ci, &ext->engines[n], sizeof(ci))) {
> +			err = -EFAULT;
> +			goto err_siblings;
> +		}
> +
> +		siblings[n] = intel_engine_lookup_user(i915,
> +						       ci.engine_class,
> +						       ci.engine_instance);
> +		if (!siblings[n]) {
> +			drm_dbg(&i915->drm,
> +				"Invalid sibling[%d]: { class:%d, inst:%d }\n",
> +				n, ci.engine_class, ci.engine_instance);
> +			err = -EINVAL;
> +			goto err_siblings;
> +		}
> +	}
> +
> +	if (num_siblings == 1) {
> +		set->engines[idx].type = I915_GEM_ENGINE_TYPE_PHYSICAL;
> +		set->engines[idx].engine = siblings[0];
> +		kfree(siblings);
> +	} else {
> +		set->engines[idx].type = I915_GEM_ENGINE_TYPE_BALANCED;
> +		set->engines[idx].num_siblings = num_siblings;
> +		set->engines[idx].siblings = siblings;
> +	}
> +
> +	return 0;
> +
> +err_siblings:
> +	kfree(siblings);
> +
> +	return err;
> +}
> +
> +static int
> +set_proto_ctx_engines_bond(struct i915_user_extension __user *base, void *data)
> +{
> +	struct i915_context_engines_bond __user *ext =
> +		container_of_user(base, typeof(*ext), base);
> +	const struct set_proto_ctx_engines *set = data;
> +	struct drm_i915_private *i915 = set->i915;
> +	struct i915_engine_class_instance ci;
> +	struct intel_engine_cs *master;
> +	u16 idx, num_bonds;
> +	int err, n;
> +
> +	if (get_user(idx, &ext->virtual_index))
> +		return -EFAULT;
> +
> +	if (idx >= set->num_engines) {
> +		drm_dbg(&i915->drm,
> +			"Invalid index for virtual engine: %d >= %d\n",
> +			idx, set->num_engines);
> +		return -EINVAL;
> +	}
> +
> +	idx = array_index_nospec(idx, set->num_engines);
> +	if (set->engines[idx].type == I915_GEM_ENGINE_TYPE_INVALID) {
> +		drm_dbg(&i915->drm, "Invalid engine at %d\n", idx);
> +		return -EINVAL;
> +	}
> +
> +	if (set->engines[idx].type != I915_GEM_ENGINE_TYPE_PHYSICAL) {
> +		drm_dbg(&i915->drm,
> +			"Bonding with virtual engines not allowed\n");
> +		return -EINVAL;
> +	}
> +
> +	err = check_user_mbz(&ext->flags);
> +	if (err)
> +		return err;
> +
> +	for (n = 0; n < ARRAY_SIZE(ext->mbz64); n++) {
> +		err = check_user_mbz(&ext->mbz64[n]);
> +		if (err)
> +			return err;
> +	}
> +
> +	if (copy_from_user(&ci, &ext->master, sizeof(ci)))
> +		return -EFAULT;
> +
> +	master = intel_engine_lookup_user(i915,
> +					  ci.engine_class,
> +					  ci.engine_instance);
> +	if (!master) {
> +		drm_dbg(&i915->drm,
> +			"Unrecognised master engine: { class:%u, instance:%u }\n",
> +			ci.engine_class, ci.engine_instance);
> +		return -EINVAL;
> +	}
> +
> +	if (get_user(num_bonds, &ext->num_bonds))
> +		return -EFAULT;
> +
> +	for (n = 0; n < num_bonds; n++) {
> +		struct intel_engine_cs *bond;
> +
> +		if (copy_from_user(&ci, &ext->engines[n], sizeof(ci)))
> +			return -EFAULT;
> +
> +		bond = intel_engine_lookup_user(i915,
> +						ci.engine_class,
> +						ci.engine_instance);
> +		if (!bond) {
> +			drm_dbg(&i915->drm,
> +				"Unrecognised engine[%d] for bonding: { class:%d, instance: %d }\n",
> +				n, ci.engine_class, ci.engine_instance);
> +			return -EINVAL;
> +		}
> +	}
> +
> +	return 0;
> +}
> +
> +static const i915_user_extension_fn set_proto_ctx_engines_extensions[] = {
> +	[I915_CONTEXT_ENGINES_EXT_LOAD_BALANCE] = set_proto_ctx_engines_balance,
> +	[I915_CONTEXT_ENGINES_EXT_BOND] = set_proto_ctx_engines_bond,
> +};
> +
> +static int set_proto_ctx_engines(struct drm_i915_file_private *fpriv,
> +			         struct i915_gem_proto_context *pc,
> +			         const struct drm_i915_gem_context_param *args)
> +{
> +	struct drm_i915_private *i915 = fpriv->dev_priv;
> +	struct set_proto_ctx_engines set = { .i915 = i915 };
> +	struct i915_context_param_engines __user *user =
> +		u64_to_user_ptr(args->value);
> +	unsigned int n;
> +	u64 extensions;
> +	int err;
> +
> +	if (!args->size) {
> +		kfree(pc->user_engines);
> +		pc->num_user_engines = -1;
> +		pc->user_engines = NULL;
> +		return 0;
> +	}
> +
> +	BUILD_BUG_ON(!IS_ALIGNED(sizeof(*user), sizeof(*user->engines)));
> +	if (args->size < sizeof(*user) ||
> +	    !IS_ALIGNED(args->size, sizeof(*user->engines))) {
> +		drm_dbg(&i915->drm, "Invalid size for engine array: %d\n",
> +			args->size);
> +		return -EINVAL;
> +	}
> +
> +	set.num_engines = (args->size - sizeof(*user)) / sizeof(*user->engines);
> +	if (set.num_engines > I915_EXEC_RING_MASK + 1)
> +		return -EINVAL;
> +
> +	set.engines = kmalloc_array(set.num_engines, sizeof(*set.engines), GFP_KERNEL);
> +	if (!set.engines)
> +		return -ENOMEM;
> +
> +	for (n = 0; n < set.num_engines; n++) {
> +		struct i915_engine_class_instance ci;
> +		struct intel_engine_cs *engine;
> +
> +		if (copy_from_user(&ci, &user->engines[n], sizeof(ci))) {
> +			kfree(set.engines);
> +			return -EFAULT;
> +		}
> +
> +		memset(&set.engines[n], 0, sizeof(set.engines[n]));
> +
> +		if (ci.engine_class == (u16)I915_ENGINE_CLASS_INVALID &&
> +		    ci.engine_instance == (u16)I915_ENGINE_CLASS_INVALID_NONE)
> +			continue;
> +
> +		engine = intel_engine_lookup_user(i915,
> +						  ci.engine_class,
> +						  ci.engine_instance);
> +		if (!engine) {
> +			drm_dbg(&i915->drm,
> +				"Invalid engine[%d]: { class:%d, instance:%d }\n",
> +				n, ci.engine_class, ci.engine_instance);
> +			kfree(set.engines);
> +			return -ENOENT;
> +		}
> +
> +		set.engines[n].type = I915_GEM_ENGINE_TYPE_PHYSICAL;
> +		set.engines[n].engine = engine;
> +	}
> +
> +	err = -EFAULT;
> +	if (!get_user(extensions, &user->extensions))
> +		err = i915_user_extensions(u64_to_user_ptr(extensions),
> +					   set_proto_ctx_engines_extensions,
> +					   ARRAY_SIZE(set_proto_ctx_engines_extensions),
> +					   &set);
> +	if (err) {
> +		kfree(set.engines);
> +		return err;
> +	}
> +
> +	kfree(pc->user_engines);
> +	pc->num_user_engines = set.num_engines;
> +	pc->user_engines = set.engines;
> +
> +	return 0;
> +}
> +
> +static int set_proto_ctx_param(struct drm_i915_file_private *fpriv,
> +			       struct i915_gem_proto_context *pc,
> +			       struct drm_i915_gem_context_param *args)
> +{
> +	int ret = 0;
> +
> +	switch (args->param) {
> +	case I915_CONTEXT_PARAM_NO_ERROR_CAPTURE:
> +		if (args->size)
> +			ret = -EINVAL;
> +		else if (args->value)
> +			set_bit(UCONTEXT_NO_ERROR_CAPTURE, &pc->user_flags);

Atomic bitops like in previous patches: Pls no :-)

> +		else
> +			clear_bit(UCONTEXT_NO_ERROR_CAPTURE, &pc->user_flags);
> +		break;
> +
> +	case I915_CONTEXT_PARAM_BANNABLE:
> +		if (args->size)
> +			ret = -EINVAL;
> +		else if (!capable(CAP_SYS_ADMIN) && !args->value)
> +			ret = -EPERM;
> +		else if (args->value)
> +			set_bit(UCONTEXT_BANNABLE, &pc->user_flags);
> +		else
> +			clear_bit(UCONTEXT_BANNABLE, &pc->user_flags);
> +		break;
> +
> +	case I915_CONTEXT_PARAM_RECOVERABLE:
> +		if (args->size)
> +			ret = -EINVAL;
> +		else if (args->value)
> +			set_bit(UCONTEXT_RECOVERABLE, &pc->user_flags);
> +		else
> +			clear_bit(UCONTEXT_RECOVERABLE, &pc->user_flags);
> +		break;
> +
> +	case I915_CONTEXT_PARAM_PRIORITY:
> +		ret = validate_priority(fpriv->dev_priv, args);
> +		if (!ret)
> +			pc->sched.priority = args->value;
> +		break;
> +
> +	case I915_CONTEXT_PARAM_SSEU:
> +		ret = -ENOTSUPP;
> +		break;
> +
> +	case I915_CONTEXT_PARAM_VM:
> +		ret = set_proto_ctx_vm(fpriv, pc, args);
> +		break;
> +
> +	case I915_CONTEXT_PARAM_ENGINES:
> +		ret = set_proto_ctx_engines(fpriv, pc, args);
> +		break;
> +
> +	case I915_CONTEXT_PARAM_PERSISTENCE:
> +		if (args->size)
> +			ret = -EINVAL;
> +		else if (args->value)
> +			set_bit(UCONTEXT_PERSISTENCE, &pc->user_flags);
> +		else
> +			clear_bit(UCONTEXT_PERSISTENCE, &pc->user_flags);
> +		break;
> +
> +	case I915_CONTEXT_PARAM_NO_ZEROMAP:
> +	case I915_CONTEXT_PARAM_BAN_PERIOD:
> +	case I915_CONTEXT_PARAM_RINGSIZE:
> +	default:
> +		ret = -EINVAL;
> +		break;
> +	}
> +
> +	return ret;
> +}
> +
>  static struct i915_address_space *
>  context_get_vm_rcu(struct i915_gem_context *ctx)
>  {
> @@ -450,6 +862,47 @@ static struct i915_gem_engines *default_engines(struct i915_gem_context *ctx)
>  	return e;
>  }
>  
> +static struct i915_gem_engines *user_engines(struct i915_gem_context *ctx,
> +					     unsigned int num_engines,
> +					     struct i915_gem_proto_engine *pe)
> +{
> +	struct i915_gem_engines *e;
> +	unsigned int n;
> +
> +	e = alloc_engines(num_engines);
> +	for (n = 0; n < num_engines; n++) {
> +		struct intel_context *ce;
> +
> +		switch (pe[n].type) {
> +		case I915_GEM_ENGINE_TYPE_PHYSICAL:
> +			ce = intel_context_create(pe[n].engine);
> +			break;
> +
> +		case I915_GEM_ENGINE_TYPE_BALANCED:
> +			ce = intel_execlists_create_virtual(pe[n].siblings,
> +							    pe[n].num_siblings);
> +			break;
> +
> +		case I915_GEM_ENGINE_TYPE_INVALID:
> +		default:
> +			GEM_WARN_ON(pe[n].type != I915_GEM_ENGINE_TYPE_INVALID);
> +			continue;
> +		}
> +
> +		if (IS_ERR(ce)) {
> +			__free_engines(e, n);
> +			return ERR_CAST(ce);
> +		}
> +
> +		intel_context_set_gem(ce, ctx);
> +
> +		e->engines[n] = ce;
> +	}
> +	e->num_engines = num_engines;
> +
> +	return e;
> +}
> +
>  void i915_gem_context_release(struct kref *ref)
>  {
>  	struct i915_gem_context *ctx = container_of(ref, typeof(*ctx), ref);
> @@ -890,6 +1343,24 @@ i915_gem_create_context(struct drm_i915_private *i915,
>  		mutex_unlock(&ctx->mutex);
>  	}
>  
> +	if (pc->num_user_engines >= 0) {
> +		struct i915_gem_engines *engines;
> +
> +		engines = user_engines(ctx, pc->num_user_engines,
> +				       pc->user_engines);
> +		if (IS_ERR(engines)) {
> +			context_close(ctx);
> +			return ERR_CAST(engines);
> +		}
> +
> +		mutex_lock(&ctx->engines_mutex);
> +		i915_gem_context_set_user_engines(ctx);
> +		engines = rcu_replace_pointer(ctx->engines, engines, 1);
> +		mutex_unlock(&ctx->engines_mutex);
> +
> +		free_engines(engines);
> +	}
> +
>  	if (pc->single_timeline) {
>  		ret = drm_syncobj_create(&ctx->syncobj,
>  					 DRM_SYNCOBJ_CREATE_SIGNALED,
> @@ -916,12 +1387,12 @@ void i915_gem_init__contexts(struct drm_i915_private *i915)
>  	init_contexts(&i915->gem.contexts);
>  }
>  
> -static int gem_context_register(struct i915_gem_context *ctx,
> -				struct drm_i915_file_private *fpriv,
> -				u32 *id)
> +static void gem_context_register(struct i915_gem_context *ctx,
> +				 struct drm_i915_file_private *fpriv,
> +				 u32 id)
>  {
>  	struct drm_i915_private *i915 = ctx->i915;
> -	int ret;
> +	void *old;
>  
>  	ctx->file_priv = fpriv;
>  
> @@ -930,19 +1401,12 @@ static int gem_context_register(struct i915_gem_context *ctx,
>  		 current->comm, pid_nr(ctx->pid));
>  
>  	/* And finally expose ourselves to userspace via the idr */
> -	ret = xa_alloc(&fpriv->context_xa, id, ctx, xa_limit_32b, GFP_KERNEL);
> -	if (ret)
> -		goto err_pid;
> +	old = xa_store(&fpriv->context_xa, id, ctx, GFP_KERNEL);
> +	GEM_BUG_ON(old);
>  
>  	spin_lock(&i915->gem.contexts.lock);
>  	list_add_tail(&ctx->link, &i915->gem.contexts.list);
>  	spin_unlock(&i915->gem.contexts.lock);
> -
> -	return 0;
> -
> -err_pid:
> -	put_pid(fetch_and_zero(&ctx->pid));
> -	return ret;
>  }
>  
>  int i915_gem_context_open(struct drm_i915_private *i915,
> @@ -952,9 +1416,12 @@ int i915_gem_context_open(struct drm_i915_private *i915,
>  	struct i915_gem_proto_context *pc;
>  	struct i915_gem_context *ctx;
>  	int err;
> -	u32 id;
>  
> -	xa_init_flags(&file_priv->context_xa, XA_FLAGS_ALLOC);
> +	mutex_init(&file_priv->proto_context_lock);
> +	xa_init_flags(&file_priv->proto_context_xa, XA_FLAGS_ALLOC);
> +
> +	/* 0 reserved for the default context */
> +	xa_init_flags(&file_priv->context_xa, XA_FLAGS_ALLOC1);
>  
>  	/* 0 reserved for invalid/unassigned ppgtt */
>  	xa_init_flags(&file_priv->vm_xa, XA_FLAGS_ALLOC1);
> @@ -972,28 +1439,31 @@ int i915_gem_context_open(struct drm_i915_private *i915,
>  		goto err;
>  	}
>  
> -	err = gem_context_register(ctx, file_priv, &id);
> -	if (err < 0)
> -		goto err_ctx;
> +	gem_context_register(ctx, file_priv, 0);
>  
> -	GEM_BUG_ON(id);
>  	return 0;
>  
> -err_ctx:
> -	context_close(ctx);
>  err:
>  	xa_destroy(&file_priv->vm_xa);
>  	xa_destroy(&file_priv->context_xa);
> +	xa_destroy(&file_priv->proto_context_xa);
> +	mutex_destroy(&file_priv->proto_context_lock);
>  	return err;
>  }
>  
>  void i915_gem_context_close(struct drm_file *file)
>  {
>  	struct drm_i915_file_private *file_priv = file->driver_priv;
> +	struct i915_gem_proto_context *pc;
>  	struct i915_address_space *vm;
>  	struct i915_gem_context *ctx;
>  	unsigned long idx;
>  
> +	xa_for_each(&file_priv->proto_context_xa, idx, pc)
> +		proto_context_close(pc);
> +	xa_destroy(&file_priv->proto_context_xa);
> +	mutex_destroy(&file_priv->proto_context_lock);
> +
>  	xa_for_each(&file_priv->context_xa, idx, ctx)
>  		context_close(ctx);
>  	xa_destroy(&file_priv->context_xa);
> @@ -1918,7 +2388,7 @@ static int ctx_setparam(struct drm_i915_file_private *fpriv,
>  }
>  
>  struct create_ext {
> -	struct i915_gem_context *ctx;
> +	struct i915_gem_proto_context *pc;
>  	struct drm_i915_file_private *fpriv;
>  };
>  
> @@ -1933,7 +2403,7 @@ static int create_setparam(struct i915_user_extension __user *ext, void *data)
>  	if (local.param.ctx_id)
>  		return -EINVAL;
>  
> -	return ctx_setparam(arg->fpriv, arg->ctx, &local.param);
> +	return set_proto_ctx_param(arg->fpriv, arg->pc, &local.param);
>  }
>  
>  static int invalid_ext(struct i915_user_extension __user *ext, void *data)
> @@ -1951,12 +2421,71 @@ static bool client_is_banned(struct drm_i915_file_private *file_priv)
>  	return atomic_read(&file_priv->ban_score) >= I915_CLIENT_SCORE_BANNED;
>  }
>  
> +static inline struct i915_gem_context *
> +__context_lookup(struct drm_i915_file_private *file_priv, u32 id)
> +{
> +	struct i915_gem_context *ctx;
> +
> +	rcu_read_lock();
> +	ctx = xa_load(&file_priv->context_xa, id);
> +	if (ctx && !kref_get_unless_zero(&ctx->ref))
> +		ctx = NULL;
> +	rcu_read_unlock();
> +
> +	return ctx;
> +}
> +
> +struct i915_gem_context *
> +lazy_create_context_locked(struct drm_i915_file_private *file_priv,
> +			   struct i915_gem_proto_context *pc, u32 id)
> +{
> +	struct i915_gem_context *ctx;
> +	void *old;

assert_lock_held is alwasy nice in all _locked functions. It entirely
compiles out without CONFIG_PROVE_LOCKING enabled.

> +
> +	ctx = i915_gem_create_context(file_priv->dev_priv, pc);

I think we need a prep patch which changes the calling convetion of this
and anything it calls to only return a NULL pointer. Then
i915_gem_context_lookup below can return the ERR_PTR(-ENOMEM) below for
that case, and we know that we're never returning a wrong error pointer.

> +	if (IS_ERR(ctx))
> +		return ctx;
> +
> +	gem_context_register(ctx, file_priv, id);
> +
> +	old = xa_erase(&file_priv->proto_context_xa, id);
> +	GEM_BUG_ON(old != pc);
> +	proto_context_close(pc);
> +
> +	/* One for the xarray and one for the caller */
> +	return i915_gem_context_get(ctx);
> +}
> +
> +struct i915_gem_context *
> +i915_gem_context_lookup(struct drm_i915_file_private *file_priv, u32 id)
> +{
> +	struct i915_gem_proto_context *pc;
> +	struct i915_gem_context *ctx;
> +
> +	ctx = __context_lookup(file_priv, id);
> +	if (ctx)
> +		return ctx;
> +
> +	mutex_lock(&file_priv->proto_context_lock);
> +	/* Try one more time under the lock */
> +	ctx = __context_lookup(file_priv, id);
> +	if (!ctx) {
> +		pc = xa_load(&file_priv->proto_context_xa, id);
> +		if (!pc)
> +			ctx = ERR_PTR(-ENOENT);
> +		else
> +			ctx = lazy_create_context_locked(file_priv, pc, id);
> +	}
> +	mutex_unlock(&file_priv->proto_context_lock);
> +
> +	return ctx;
> +}
> +
>  int i915_gem_context_create_ioctl(struct drm_device *dev, void *data,
>  				  struct drm_file *file)
>  {
>  	struct drm_i915_private *i915 = to_i915(dev);
>  	struct drm_i915_gem_context_create_ext *args = data;
> -	struct i915_gem_proto_context *pc;
>  	struct create_ext ext_data;
>  	int ret;
>  	u32 id;
> @@ -1979,14 +2508,9 @@ int i915_gem_context_create_ioctl(struct drm_device *dev, void *data,
>  		return -EIO;
>  	}
>  
> -	pc = proto_context_create(i915, args->flags);
> -	if (IS_ERR(pc))
> -		return PTR_ERR(pc);
> -
> -	ext_data.ctx = i915_gem_create_context(i915, pc);
> -	proto_context_close(pc);
> -	if (IS_ERR(ext_data.ctx))
> -		return PTR_ERR(ext_data.ctx);
> +	ext_data.pc = proto_context_create(i915, args->flags);
> +	if (IS_ERR(ext_data.pc))
> +		return PTR_ERR(ext_data.pc);
>  
>  	if (args->flags & I915_CONTEXT_CREATE_FLAGS_USE_EXTENSIONS) {
>  		ret = i915_user_extensions(u64_to_user_ptr(args->extensions),
> @@ -1994,20 +2518,20 @@ int i915_gem_context_create_ioctl(struct drm_device *dev, void *data,
>  					   ARRAY_SIZE(create_extensions),
>  					   &ext_data);
>  		if (ret)
> -			goto err_ctx;
> +			goto err_pc;
>  	}
>  
> -	ret = gem_context_register(ext_data.ctx, ext_data.fpriv, &id);
> +	ret = proto_context_register(ext_data.fpriv, ext_data.pc, &id);
>  	if (ret < 0)
> -		goto err_ctx;
> +		goto err_pc;
>  
>  	args->ctx_id = id;
>  	drm_dbg(&i915->drm, "HW context %d created\n", args->ctx_id);
>  
>  	return 0;
>  
> -err_ctx:
> -	context_close(ext_data.ctx);
> +err_pc:
> +	proto_context_close(ext_data.pc);
>  	return ret;
>  }
>  
> @@ -2016,6 +2540,7 @@ int i915_gem_context_destroy_ioctl(struct drm_device *dev, void *data,
>  {
>  	struct drm_i915_gem_context_destroy *args = data;
>  	struct drm_i915_file_private *file_priv = file->driver_priv;
> +	struct i915_gem_proto_context *pc;
>  	struct i915_gem_context *ctx;
>  
>  	if (args->pad != 0)
> @@ -2024,11 +2549,21 @@ int i915_gem_context_destroy_ioctl(struct drm_device *dev, void *data,
>  	if (!args->ctx_id)
>  		return -ENOENT;
>  
> +	mutex_lock(&file_priv->proto_context_lock);
>  	ctx = xa_erase(&file_priv->context_xa, args->ctx_id);
> -	if (!ctx)
> +	pc = xa_erase(&file_priv->proto_context_xa, args->ctx_id);
> +	mutex_unlock(&file_priv->proto_context_lock);
> +
> +	if (!ctx && !pc)
>  		return -ENOENT;
> +	GEM_WARN_ON(ctx && pc);
> +
> +	if (pc)
> +		proto_context_close(pc);
> +
> +	if (ctx)
> +		context_close(ctx);
>  
> -	context_close(ctx);
>  	return 0;
>  }
>  
> @@ -2161,16 +2696,48 @@ int i915_gem_context_setparam_ioctl(struct drm_device *dev, void *data,
>  {
>  	struct drm_i915_file_private *file_priv = file->driver_priv;
>  	struct drm_i915_gem_context_param *args = data;
> +	struct i915_gem_proto_context *pc;
>  	struct i915_gem_context *ctx;
> -	int ret;
> +	int ret = 0;
>  
> -	ctx = i915_gem_context_lookup(file_priv, args->ctx_id);
> -	if (IS_ERR(ctx))
> -		return PTR_ERR(ctx);
> +	ctx = __context_lookup(file_priv, args->ctx_id);
> +	if (ctx)
> +		goto set_ctx_param;
>  
> -	ret = ctx_setparam(file_priv, ctx, args);
> +	mutex_lock(&file_priv->proto_context_lock);
> +	ctx = __context_lookup(file_priv, args->ctx_id);
> +	if (ctx)
> +		goto unlock;
> +
> +	pc = xa_load(&file_priv->proto_context_xa, args->ctx_id);
> +	if (!pc) {
> +		ret = -ENOENT;
> +		goto unlock;
> +	}
> +
> +	ret = set_proto_ctx_param(file_priv, pc, args);

I think we should have a FIXME here of not allowing this on some future
platforms because just use CTX_CREATE_EXT.

> +	if (ret == -ENOTSUPP) {
> +		/* Some params, specifically SSEU, can only be set on fully

I think this needs a FIXME: that this only holds during the conversion?
Otherwise we kinda have a bit a problem me thinks ...


> +		 * created contexts.
> +		 */
> +		ret = 0;
> +		ctx = lazy_create_context_locked(file_priv, pc, args->ctx_id);
> +		if (IS_ERR(ctx)) {
> +			ret = PTR_ERR(ctx);
> +			ctx = NULL;
> +		}
> +	}
> +
> +unlock:
> +	mutex_unlock(&file_priv->proto_context_lock);
> +
> +set_ctx_param:
> +	if (!ret && ctx)
> +		ret = ctx_setparam(file_priv, ctx, args);
> +
> +	if (ctx)
> +		i915_gem_context_put(ctx);
>  
> -	i915_gem_context_put(ctx);
>  	return ret;
>  }
>  
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.h b/drivers/gpu/drm/i915/gem/i915_gem_context.h
> index b5c908f3f4f22..20411db84914a 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_context.h
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.h
> @@ -133,6 +133,9 @@ int i915_gem_context_setparam_ioctl(struct drm_device *dev, void *data,
>  int i915_gem_context_reset_stats_ioctl(struct drm_device *dev, void *data,
>  				       struct drm_file *file);
>  
> +struct i915_gem_context *
> +i915_gem_context_lookup(struct drm_i915_file_private *file_priv, u32 id);
> +
>  static inline struct i915_gem_context *
>  i915_gem_context_get(struct i915_gem_context *ctx)
>  {
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context_types.h b/drivers/gpu/drm/i915/gem/i915_gem_context_types.h
> index a42c429f94577..067ea3030ac91 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_context_types.h
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_context_types.h
> @@ -46,6 +46,26 @@ struct i915_gem_engines_iter {
>  	const struct i915_gem_engines *engines;
>  };
>  
> +enum i915_gem_engine_type {
> +	I915_GEM_ENGINE_TYPE_INVALID = 0,
> +	I915_GEM_ENGINE_TYPE_PHYSICAL,
> +	I915_GEM_ENGINE_TYPE_BALANCED,
> +};
> +

Some kerneldoc missing?

> +struct i915_gem_proto_engine {
> +	/** @type: Type of this engine */
> +	enum i915_gem_engine_type type;
> +
> +	/** @num_siblings: Engine, for physical */
> +	struct intel_engine_cs *engine;
> +
> +	/** @num_siblings: Number of balanced siblings */
> +	unsigned int num_siblings;
> +
> +	/** @num_siblings: Balanced siblings */
> +	struct intel_engine_cs **siblings;

I guess you're stuffing both balanced and siblings into one?
> +};
> +
>  /**
>   * struct i915_gem_proto_context - prototype context
>   *
> @@ -64,6 +84,12 @@ struct i915_gem_proto_context {
>  	/** @sched: See i915_gem_context::sched */
>  	struct i915_sched_attr sched;
>  
> +	/** @num_user_engines: Number of user-specified engines or -1 */
> +	int num_user_engines;
> +
> +	/** @num_user_engines: User-specified engines */
> +	struct i915_gem_proto_engine *user_engines;
> +
>  	bool single_timeline;
>  };
>  
> diff --git a/drivers/gpu/drm/i915/gem/selftests/mock_context.c b/drivers/gpu/drm/i915/gem/selftests/mock_context.c
> index e0f512ef7f3c6..32cf2103828f9 100644
> --- a/drivers/gpu/drm/i915/gem/selftests/mock_context.c
> +++ b/drivers/gpu/drm/i915/gem/selftests/mock_context.c
> @@ -80,6 +80,7 @@ void mock_init_contexts(struct drm_i915_private *i915)
>  struct i915_gem_context *
>  live_context(struct drm_i915_private *i915, struct file *file)
>  {
> +	struct drm_i915_file_private *fpriv = to_drm_file(file)->driver_priv;
>  	struct i915_gem_proto_context *pc;
>  	struct i915_gem_context *ctx;
>  	int err;
> @@ -96,10 +97,12 @@ live_context(struct drm_i915_private *i915, struct file *file)
>  
>  	i915_gem_context_set_no_error_capture(ctx);
>  
> -	err = gem_context_register(ctx, to_drm_file(file)->driver_priv, &id);
> +	err = xa_alloc(&fpriv->context_xa, &id, NULL, xa_limit_32b, GFP_KERNEL);
>  	if (err < 0)
>  		goto err_ctx;
>  
> +	gem_context_register(ctx, fpriv, id);
> +
>  	return ctx;
>  
>  err_ctx:
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 004ed0e59c999..365c042529d72 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -200,6 +200,9 @@ struct drm_i915_file_private {
>  		struct rcu_head rcu;
>  	};
>  
> +	struct mutex proto_context_lock;
> +	struct xarray proto_context_xa;

Kerneldoc here please. Ideally also for the context_xa below (but maybe
that's for later).

Also please add a hint to the proto context struct that it's all fully
protected by proto_context_lock above and is never visible outside of
that.

> +
>  	struct xarray context_xa;
>  	struct xarray vm_xa;
>  
> @@ -1840,20 +1843,6 @@ struct drm_gem_object *i915_gem_prime_import(struct drm_device *dev,
>  
>  struct dma_buf *i915_gem_prime_export(struct drm_gem_object *gem_obj, int flags);
>  
> -static inline struct i915_gem_context *
> -i915_gem_context_lookup(struct drm_i915_file_private *file_priv, u32 id)
> -{
> -	struct i915_gem_context *ctx;
> -
> -	rcu_read_lock();
> -	ctx = xa_load(&file_priv->context_xa, id);
> -	if (ctx && !kref_get_unless_zero(&ctx->ref))
> -		ctx = NULL;
> -	rcu_read_unlock();
> -
> -	return ctx ? ctx : ERR_PTR(-ENOENT);
> -}
> -
>  /* i915_gem_evict.c */
>  int __must_check i915_gem_evict_something(struct i915_address_space *vm,
>  					  u64 min_size, u64 alignment,

I think I'll check details when I'm not getting distracted by the
vm/engines validation code that I think shouldn't be here :-)
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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