Re: [PATCH v8 22/22] drm/i915/vm_bind: Support capture of persistent mappings

From: Matthew Auld <matthew.auld@intel.com>
To: Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>,
	intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org
Cc: matthew.brost@intel.com, paulo.r.zanoni@intel.com,
	tvrtko.ursulin@intel.com, jani.nikula@intel.com,
	lionel.g.landwerlin@intel.com, thomas.hellstrom@intel.com,
	jason@jlekstrand.net, andi.shyti@linux.intel.com,
	daniel.vetter@intel.com, christian.koenig@amd.com
Subject: Re: [PATCH v8 22/22] drm/i915/vm_bind: Support capture of persistent mappings
Date: Thu, 1 Dec 2022 10:49:15 +0000	[thread overview]
Message-ID: <dbbd19e4-4354-bd11-a68d-435f59150fc8@intel.com> (raw)
In-Reply-To: <20221129072635.847-23-niranjana.vishwanathapura@intel.com>

On 29/11/2022 07:26, Niranjana Vishwanathapura wrote:
> Support dump capture of persistent mappings upon user request.
> 
> Signed-off-by: Brian Welty <brian.welty@intel.com>
> Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>
> ---
>   .../drm/i915/gem/i915_gem_vm_bind_object.c    | 11 +++++++++++
>   drivers/gpu/drm/i915/gt/intel_gtt.c           |  3 +++
>   drivers/gpu/drm/i915/gt/intel_gtt.h           |  5 +++++
>   drivers/gpu/drm/i915/i915_gpu_error.c         | 19 +++++++++++++++++++
>   drivers/gpu/drm/i915/i915_vma.c               |  1 +
>   drivers/gpu/drm/i915/i915_vma_types.h         |  2 ++
>   include/uapi/drm/i915_drm.h                   |  3 ++-
>   7 files changed, 43 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_vm_bind_object.c b/drivers/gpu/drm/i915/gem/i915_gem_vm_bind_object.c
> index 78e7c0642c5f..50969613daf6 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_vm_bind_object.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_vm_bind_object.c
> @@ -88,6 +88,11 @@ static void i915_gem_vm_bind_remove(struct i915_vma *vma, bool release_obj)
>   {
>   	lockdep_assert_held(&vma->vm->vm_bind_lock);
>   
> +	spin_lock(&vma->vm->vm_capture_lock);
> +	if (!list_empty(&vma->vm_capture_link))
> +		list_del_init(&vma->vm_capture_link);
> +	spin_unlock(&vma->vm->vm_capture_lock);
> +
>   	spin_lock(&vma->vm->vm_rebind_lock);
>   	if (!list_empty(&vma->vm_rebind_link))
>   		list_del_init(&vma->vm_rebind_link);
> @@ -357,6 +362,12 @@ static int i915_gem_vm_bind_obj(struct i915_address_space *vm,
>   				continue;
>   		}
>   
> +		if (va->flags & I915_GEM_VM_BIND_CAPTURE) {
> +			spin_lock(&vm->vm_capture_lock);
> +			list_add_tail(&vma->vm_capture_link, &vm->vm_capture_list);
> +			spin_unlock(&vm->vm_capture_lock);
> +		}
> +
>   		list_add_tail(&vma->vm_bind_link, &vm->vm_bound_list);
>   		i915_vm_bind_it_insert(vma, &vm->va);
>   		if (!obj->priv_root)
> diff --git a/drivers/gpu/drm/i915/gt/intel_gtt.c b/drivers/gpu/drm/i915/gt/intel_gtt.c
> index ebf6830574a0..bdabe13fc30e 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gtt.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gtt.c
> @@ -297,6 +297,9 @@ void i915_address_space_init(struct i915_address_space *vm, int subclass)
>   	spin_lock_init(&vm->vm_rebind_lock);
>   	spin_lock_init(&vm->userptr_invalidated_lock);
>   	INIT_LIST_HEAD(&vm->userptr_invalidated_list);
> +
> +	INIT_LIST_HEAD(&vm->vm_capture_list);
> +	spin_lock_init(&vm->vm_capture_lock);
>   }
>   
>   void *__px_vaddr(struct drm_i915_gem_object *p)
> diff --git a/drivers/gpu/drm/i915/gt/intel_gtt.h b/drivers/gpu/drm/i915/gt/intel_gtt.h
> index 87e5b6568a00..8e4ddd073348 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gtt.h
> +++ b/drivers/gpu/drm/i915/gt/intel_gtt.h
> @@ -281,6 +281,11 @@ struct i915_address_space {
>   	/** @root_obj: root object for dma-resv sharing by private objects */
>   	struct drm_i915_gem_object *root_obj;
>   
> +	/* @vm_capture_list: list of vm captures */
> +	struct list_head vm_capture_list;
> +	/* @vm_capture_lock: protects vm_capture_list */
> +	spinlock_t vm_capture_lock;
> +
>   	/* Global GTT */
>   	bool is_ggtt:1;
>   
> diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
> index 9d5d5a397b64..3b2b12a739f7 100644
> --- a/drivers/gpu/drm/i915/i915_gpu_error.c
> +++ b/drivers/gpu/drm/i915/i915_gpu_error.c
> @@ -1460,6 +1460,22 @@ capture_vma(struct intel_engine_capture_vma *next,
>   	return next;
>   }
>   
> +static struct intel_engine_capture_vma *
> +capture_user_vm(struct intel_engine_capture_vma *capture,
> +		struct i915_address_space *vm, gfp_t gfp)
> +{
> +	struct i915_vma *vma;
> +
> +	spin_lock(&vm->vm_capture_lock);

Does it make sense to move this into the eb3 submission stage, like we 
do for eb2? IIRC the gfp flags here are quite limiting due to 
potentially being in a fence critical section. If we can use 
rq->capture_list for eb3, we shouldn't need to change much here?

Also there is the existing CONFIG_DRM_I915_CAPTURE_ERROR. Should we take 
that into account?

> +	/* vma->resource must be valid here as persistent vmas are bound */
> +	list_for_each_entry(vma, &vm->vm_capture_list, vm_capture_link)
> +		capture = capture_vma_snapshot(capture, vma->resource,
> +					       gfp, "user");
> +	spin_unlock(&vm->vm_capture_lock);
> +
> +	return capture;
> +}
> +
>   static struct intel_engine_capture_vma *
>   capture_user(struct intel_engine_capture_vma *capture,
>   	     const struct i915_request *rq,
> @@ -1471,6 +1487,9 @@ capture_user(struct intel_engine_capture_vma *capture,
>   		capture = capture_vma_snapshot(capture, c->vma_res, gfp,
>   					       "user");
>   
> +	capture = capture_user_vm(capture, rq->context->vm,
> +				  GFP_NOWAIT | __GFP_NOWARN);

And this should maybe use the passed in gfp?

> +
>   	return capture;
>   }
>   
> diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
> index 68a9ac77b4f2..0244864e94f7 100644
> --- a/drivers/gpu/drm/i915/i915_vma.c
> +++ b/drivers/gpu/drm/i915/i915_vma.c
> @@ -248,6 +248,7 @@ vma_create(struct drm_i915_gem_object *obj,
>   	INIT_LIST_HEAD(&vma->non_priv_vm_bind_link);
>   	INIT_LIST_HEAD(&vma->vm_rebind_link);
>   	INIT_LIST_HEAD(&vma->userptr_invalidated_link);
> +	INIT_LIST_HEAD(&vma->vm_capture_link);
>   	return vma;
>   
>   err_unlock:
> diff --git a/drivers/gpu/drm/i915/i915_vma_types.h b/drivers/gpu/drm/i915/i915_vma_types.h
> index 90471dc0b235..10ae9f739d57 100644
> --- a/drivers/gpu/drm/i915/i915_vma_types.h
> +++ b/drivers/gpu/drm/i915/i915_vma_types.h
> @@ -309,6 +309,8 @@ struct i915_vma {
>   	struct list_head vm_rebind_link; /* Link in vm_rebind_list */
>   	/** @userptr_invalidated_link: link to the vm->userptr_invalidated_list */
>   	struct list_head userptr_invalidated_link;
> +	/* @vm_capture_link: link to the captureable VMA list */
> +	struct list_head vm_capture_link;
>   
>   	/** Timeline fence for vm_bind completion notification */
>   	struct {
> diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
> index b9167f950327..0744651ad5b0 100644
> --- a/include/uapi/drm/i915_drm.h
> +++ b/include/uapi/drm/i915_drm.h
> @@ -3930,7 +3930,8 @@ struct drm_i915_gem_vm_bind {
>   	 * Note that @fence carries its own flags.
>   	 */
>   	__u64 flags;
> -#define __I915_GEM_VM_BIND_UNKNOWN_FLAGS (~0ull)
> +#define I915_GEM_VM_BIND_CAPTURE           (1 << 0)

1ull << 0

Worried about what the value of UNKNOWN_FLAGS might be otherwise? Also 
needs some kernel-doc.

> +#define __I915_GEM_VM_BIND_UNKNOWN_FLAGS   (-(I915_GEM_VM_BIND_CAPTURE << 1))
>   
>   	/** @rsvd: Reserved, MBZ */
>   	__u64 rsvd[2];