linux-kernel - Re: [PATCH 1/3] drm/panfrost: Add BO labelling to Panfrost

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Message-ID: <20250507162545.3475be0d@collabora.com>
Date: Wed, 7 May 2025 16:25:45 +0200
From: Boris Brezillon <boris.brezillon@...labora.com>
To: Adrián Larumbe <adrian.larumbe@...labora.com>
Cc: linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
 kernel@...labora.com, Rob Herring <robh@...nel.org>, Steven Price
 <steven.price@....com>, Maarten Lankhorst
 <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>,
 Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>
Subject: Re: [PATCH 1/3] drm/panfrost: Add BO labelling to Panfrost

On Wed, 7 May 2025 14:01:04 +0100
Adrián Larumbe <adrian.larumbe@...labora.com> wrote:

> On 06.05.2025 08:54, Boris Brezillon wrote:
> > On Thu, 24 Apr 2025 03:21:30 +0100
> > Adrián Larumbe <adrian.larumbe@...labora.com> wrote:
> >  
> > > Unlike in Panthor, from where this change is based on, there is no need
> > > to support tagging of BO's other than UM-exposed ones, so all strings
> > > can be freed with kfree().
> > >
> > > This commit is done in preparation of a following one that will allow
> > > UM to set BO labels through a new ioctl().
> > >
> > > Signed-off-by: Adrián Larumbe <adrian.larumbe@...labora.com>
> > > ---
> > >  drivers/gpu/drm/panfrost/panfrost_gem.c | 19 +++++++++++++++++++
> > >  drivers/gpu/drm/panfrost/panfrost_gem.h | 16 ++++++++++++++++
> > >  2 files changed, 35 insertions(+)
> > >
> > > diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.c b/drivers/gpu/drm/panfrost/panfrost_gem.c
> > > index 963f04ba2de6..a7a29974d8b1 100644
> > > --- a/drivers/gpu/drm/panfrost/panfrost_gem.c
> > > +++ b/drivers/gpu/drm/panfrost/panfrost_gem.c
> > > @@ -1,6 +1,7 @@
> > >  // SPDX-License-Identifier: GPL-2.0
> > >  /* Copyright 2019 Linaro, Ltd, Rob Herring <robh@...nel.org> */
> > >
> > > +#include <linux/cleanup.h>
> > >  #include <linux/err.h>
> > >  #include <linux/slab.h>
> > >  #include <linux/dma-buf.h>
> > > @@ -35,6 +36,9 @@ static void panfrost_gem_free_object(struct drm_gem_object *obj)
> > >  	 */
> > >  	WARN_ON_ONCE(!list_empty(&bo->mappings.list));
> > >
> > > +	kfree(bo->label.str);
> > > +	mutex_destroy(&bo->label.lock);
> > > +
> > >  	if (bo->sgts) {
> > >  		int i;
> > >  		int n_sgt = bo->base.base.size / SZ_2M;
> > > @@ -260,6 +264,7 @@ struct drm_gem_object *panfrost_gem_create_object(struct drm_device *dev, size_t
> > >  	mutex_init(&obj->mappings.lock);
> > >  	obj->base.base.funcs = &panfrost_gem_funcs;
> > >  	obj->base.map_wc = !pfdev->coherent;
> > > +	mutex_init(&obj->label.lock);
> > >
> > >  	return &obj->base.base;
> > >  }
> > > @@ -302,3 +307,17 @@ panfrost_gem_prime_import_sg_table(struct drm_device *dev,
> > >
> > >  	return obj;
> > >  }
> > > +
> > > +void
> > > +panfrost_gem_set_label(struct drm_gem_object *obj, const char *label)
> > > +{
> > > +	struct panfrost_gem_object *bo = to_panfrost_bo(obj);
> > > +	const char *old_label;
> > > +
> > > +	scoped_guard(mutex, &bo->label.lock) {
> > > +		old_label = bo->label.str;
> > > +		bo->label.str = label;
> > > +	}
> > > +
> > > +	kfree(old_label);
> > > +}
> > > diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.h b/drivers/gpu/drm/panfrost/panfrost_gem.h
> > > index 7516b7ecf7fe..c0be2934f229 100644
> > > --- a/drivers/gpu/drm/panfrost/panfrost_gem.h
> > > +++ b/drivers/gpu/drm/panfrost/panfrost_gem.h
> > > @@ -41,6 +41,20 @@ struct panfrost_gem_object {
> > >  	 */
> > >  	size_t heap_rss_size;
> > >
> > > +	/**
> > > +	 * @label: BO tagging fields. The label can be assigned within the
> > > +	 * driver itself or through a specific IOCTL.
> > > +	 */
> > > +	struct {
> > > +		/**
> > > +		 * @label.str: Pointer to NULL-terminated string,
> > > +		 */
> > > +		const char *str;
> > > +
> > > +		/** @lock.str: Protects access to the @label.str field. */
> > > +		struct mutex lock;
> > > +	} label;  
> >
> > Can we do as we did in panthor, and put those fields in the debugfs
> > field.  
> 
> BO labelling fields must be present outside of DebugFS builds.

Hm, right. I see those are not in an #ifdef CONFIG_DEBUGFS section in
panthor. I don't really see a good reason to store labels if we don't
have a way to retrieve/display them, but I guess that'd make sense if
we introduce a GET_LABEL ioctl.

> 
> > +
> >  	bool noexec		:1;
> >  	bool is_heap		:1;
> >  };
> > @@ -89,4 +103,6 @@ void panfrost_gem_teardown_mappings_locked(struct panfrost_gem_object *bo);
> >  int panfrost_gem_shrinker_init(struct drm_device *dev);
> >  void panfrost_gem_shrinker_cleanup(struct drm_device *dev);
> >
> > +void panfrost_gem_set_label(struct drm_gem_object *obj, const char *label);
> > +
> >  #endif /* __PANFROST_GEM_H__ */  
> 
> 
> Adrian Larumbe