Introduce the 'panthor.transparent_hugepage' boolean module parameter
(false by default). When the parameter is set to true, a new tmpfs
mount point is created and mounted using the 'huge=within_size'
option. It's then used at GEM object creation instead of the default
'shm_mnt' mount point in order to enable Transparent Hugepage (THP)
for the object (without having to rely on a system wide parameter).

Signed-off-by: Loïc Molinari <loic.molinari@collabora.com>
---
 drivers/gpu/drm/panthor/panthor_device.c |  4 ++++
 drivers/gpu/drm/panthor/panthor_device.h |  3 +++
 drivers/gpu/drm/panthor/panthor_drv.c    |  7 ++++++
 drivers/gpu/drm/panthor/panthor_drv.h    | 11 +++++++++
 drivers/gpu/drm/panthor/panthor_gem.c    | 30 +++++++++++++++++++++++-
 drivers/gpu/drm/panthor/panthor_gem.h    |  3 +++
 6 files changed, 57 insertions(+), 1 deletion(-)
 create mode 100644 drivers/gpu/drm/panthor/panthor_drv.h

diff --git a/drivers/gpu/drm/panthor/panthor_device.c b/drivers/gpu/drm/panthor/panthor_device.c
index 81df49880bd8..4f254b574287 100644
--- a/drivers/gpu/drm/panthor/panthor_device.c
+++ b/drivers/gpu/drm/panthor/panthor_device.c
@@ -17,6 +17,7 @@
 #include "panthor_devfreq.h"
 #include "panthor_device.h"
 #include "panthor_fw.h"
+#include "panthor_gem.h"
 #include "panthor_gpu.h"
 #include "panthor_hw.h"
 #include "panthor_mmu.h"
@@ -98,6 +99,7 @@ void panthor_device_unplug(struct panthor_device *ptdev)
 	/* Now, try to cleanly shutdown the GPU before the device resources
 	 * get reclaimed.
 	 */
+	panthor_gem_fini(ptdev);
 	panthor_sched_unplug(ptdev);
 	panthor_fw_unplug(ptdev);
 	panthor_mmu_unplug(ptdev);
@@ -269,6 +271,8 @@ int panthor_device_init(struct panthor_device *ptdev)
 	if (ret)
 		goto err_unplug_fw;
 
+	panthor_gem_init(ptdev);
+
 	/* ~3 frames */
 	pm_runtime_set_autosuspend_delay(ptdev->base.dev, 50);
 	pm_runtime_use_autosuspend(ptdev->base.dev);
diff --git a/drivers/gpu/drm/panthor/panthor_device.h b/drivers/gpu/drm/panthor/panthor_device.h
index 4fc7cf2aeed5..54ca61567426 100644
--- a/drivers/gpu/drm/panthor/panthor_device.h
+++ b/drivers/gpu/drm/panthor/panthor_device.h
@@ -135,6 +135,9 @@ struct panthor_device {
 	/** @devfreq: Device frequency scaling management data. */
 	struct panthor_devfreq *devfreq;
 
+	/** @huge_mnt: tmpfs mount point with Transparent Hugepage enabled. */
+	struct vfsmount *huge_mnt;
+
 	/** @unplug: Device unplug related fields. */
 	struct {
 		/** @lock: Lock used to serialize unplug operations. */
diff --git a/drivers/gpu/drm/panthor/panthor_drv.c b/drivers/gpu/drm/panthor/panthor_drv.c
index fdbe89ef7f43..a2be3b904ca2 100644
--- a/drivers/gpu/drm/panthor/panthor_drv.c
+++ b/drivers/gpu/drm/panthor/panthor_drv.c
@@ -1556,6 +1556,7 @@ static const struct file_operations panthor_drm_driver_fops = {
 	.read = drm_read,
 	.llseek = noop_llseek,
 	.mmap = panthor_mmap,
+	.get_unmapped_area = drm_gem_get_unmapped_area,
 	.show_fdinfo = drm_show_fdinfo,
 	.fop_flags = FOP_UNSIGNED_OFFSET,
 };
@@ -1623,6 +1624,12 @@ static const struct drm_driver panthor_drm_driver = {
 #endif
 };
 
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+bool panthor_transparent_hugepage;
+module_param_named(transparent_hugepage, panthor_transparent_hugepage, bool, 0400);
+MODULE_PARM_DESC(transparent_hugepage, "Use a dedicated tmpfs mount point with Transparent Hugepage enabled (false = default)");
+#endif
+
 static int panthor_probe(struct platform_device *pdev)
 {
 	struct panthor_device *ptdev;
diff --git a/drivers/gpu/drm/panthor/panthor_drv.h b/drivers/gpu/drm/panthor/panthor_drv.h
new file mode 100644
index 000000000000..27fe9b6f77bd
--- /dev/null
+++ b/drivers/gpu/drm/panthor/panthor_drv.h
@@ -0,0 +1,11 @@
+// SPDX-License-Identifier: GPL-2.0 or MIT
+/* Copyright 2025 Amazon.com, Inc. or its affiliates */
+
+#ifndef __PANTHOR_DRV_H__
+#define __PANTHOR_DRV_H__
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+extern bool panthor_transparent_hugepage;
+#endif
+
+#endif
diff --git a/drivers/gpu/drm/panthor/panthor_gem.c b/drivers/gpu/drm/panthor/panthor_gem.c
index 156c7a0b62a2..16916e0b6d89 100644
--- a/drivers/gpu/drm/panthor/panthor_gem.c
+++ b/drivers/gpu/drm/panthor/panthor_gem.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0 or MIT
 /* Copyright 2019 Linaro, Ltd, Rob Herring <robh@kernel.org> */
 /* Copyright 2023 Collabora ltd. */
+/* Copyright 2025 Amazon.com, Inc. or its affiliates */
 
 #include <linux/cleanup.h>
 #include <linux/dma-buf.h>
@@ -11,10 +12,35 @@
 #include <drm/panthor_drm.h>
 
 #include "panthor_device.h"
+#include "panthor_drv.h"
 #include "panthor_fw.h"
 #include "panthor_gem.h"
 #include "panthor_mmu.h"
 
+void panthor_gem_init(struct panthor_device *ptdev)
+{
+	struct vfsmount *huge_mnt;
+
+	if (!panthor_transparent_hugepage)
+		return;
+
+	huge_mnt = drm_gem_shmem_huge_mnt_create("within_size");
+	if (IS_ERR(huge_mnt)) {
+		drm_warn(&ptdev->base, "Can't use Transparent Hugepage (%ld)\n",
+			 PTR_ERR(huge_mnt));
+		return;
+	}
+
+	ptdev->huge_mnt = huge_mnt;
+
+	drm_info(&ptdev->base, "Using Transparent Hugepage\n");
+}
+
+void panthor_gem_fini(struct panthor_device *ptdev)
+{
+	drm_gem_shmem_huge_mnt_free(ptdev->huge_mnt);
+}
+
 #ifdef CONFIG_DEBUG_FS
 static void panthor_gem_debugfs_bo_init(struct panthor_gem_object *bo)
 {
@@ -270,10 +296,12 @@ panthor_gem_create_with_handle(struct drm_file *file,
 			       u64 *size, u32 flags, u32 *handle)
 {
 	int ret;
+	struct panthor_device *ptdev =
+		container_of(ddev, struct panthor_device, base);
 	struct drm_gem_shmem_object *shmem;
 	struct panthor_gem_object *bo;
 
-	shmem = drm_gem_shmem_create(ddev, *size);
+	shmem = drm_gem_shmem_create_with_mnt(ddev, *size, ptdev->huge_mnt);
 	if (IS_ERR(shmem))
 		return PTR_ERR(shmem);
 
diff --git a/drivers/gpu/drm/panthor/panthor_gem.h b/drivers/gpu/drm/panthor/panthor_gem.h
index 80c6e24112d0..6804b3912cc2 100644
--- a/drivers/gpu/drm/panthor/panthor_gem.h
+++ b/drivers/gpu/drm/panthor/panthor_gem.h
@@ -136,6 +136,9 @@ struct panthor_gem_object *to_panthor_bo(struct drm_gem_object *obj)
 	return container_of(to_drm_gem_shmem_obj(obj), struct panthor_gem_object, base);
 }
 
+void panthor_gem_init(struct panthor_device *ptdev);
+void panthor_gem_fini(struct panthor_device *ptdev);
+
 struct drm_gem_object *panthor_gem_create_object(struct drm_device *ddev, size_t size);
 
 int
-- 
2.47.3

Hi Loïc,

kernel test robot noticed the following build errors:

[auto build test ERROR on drm-misc/drm-misc-next]
[cannot apply to akpm-mm/mm-everything linus/master v6.17 next-20250929]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Lo-c-Molinari/drm-shmem-helper-Add-huge-page-fault-handler/20250930-040600
base:   git://anongit.freedesktop.org/drm/drm-misc drm-misc-next
patch link:    https://lore.kernel.org/r/20250929200316.18417-7-loic.molinari%40collabora.com
patch subject: [PATCH 6/8] drm/panthor: Introduce huge tmpfs mount point option
config: i386-buildonly-randconfig-004-20250930 (https://download.01.org/0day-ci/archive/20250930/202509301834.aoEcLO0C-lkp@intel.com/config)
compiler: gcc-14 (Debian 14.2.0-19) 14.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250930/202509301834.aoEcLO0C-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202509301834.aoEcLO0C-lkp@intel.com/

All errors (new ones prefixed by >>):

   drivers/gpu/drm/panthor/panthor_gem.c: In function 'panthor_gem_init':
>> drivers/gpu/drm/panthor/panthor_gem.c:24:14: error: 'panthor_transparent_hugepage' undeclared (first use in this function); did you mean 'has_transparent_hugepage'?
      24 |         if (!panthor_transparent_hugepage)
         |              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
         |              has_transparent_hugepage
   drivers/gpu/drm/panthor/panthor_gem.c:24:14: note: each undeclared identifier is reported only once for each function it appears in


vim +24 drivers/gpu/drm/panthor/panthor_gem.c

    19	
    20	void panthor_gem_init(struct panthor_device *ptdev)
    21	{
    22		struct vfsmount *huge_mnt;
    23	
  > 24		if (!panthor_transparent_hugepage)
    25			return;
    26	
    27		huge_mnt = drm_gem_shmem_huge_mnt_create("within_size");
    28		if (IS_ERR(huge_mnt)) {
    29			drm_warn(&ptdev->base, "Can't use Transparent Hugepage (%ld)\n",
    30				 PTR_ERR(huge_mnt));
    31			return;
    32		}
    33	
    34		ptdev->huge_mnt = huge_mnt;
    35	
    36		drm_info(&ptdev->base, "Using Transparent Hugepage\n");
    37	}
    38	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

On Mon, 29 Sep 2025 22:03:14 +0200
Loïc Molinari <loic.molinari@collabora.com> wrote:

> Introduce the 'panthor.transparent_hugepage' boolean module parameter
> (false by default). When the parameter is set to true, a new tmpfs
> mount point is created and mounted using the 'huge=within_size'
> option. It's then used at GEM object creation instead of the default
> 'shm_mnt' mount point in order to enable Transparent Hugepage (THP)
> for the object (without having to rely on a system wide parameter).
> 
> Signed-off-by: Loïc Molinari <loic.molinari@collabora.com>
> ---
>  drivers/gpu/drm/panthor/panthor_device.c |  4 ++++
>  drivers/gpu/drm/panthor/panthor_device.h |  3 +++
>  drivers/gpu/drm/panthor/panthor_drv.c    |  7 ++++++
>  drivers/gpu/drm/panthor/panthor_drv.h    | 11 +++++++++
>  drivers/gpu/drm/panthor/panthor_gem.c    | 30 +++++++++++++++++++++++-
>  drivers/gpu/drm/panthor/panthor_gem.h    |  3 +++
>  6 files changed, 57 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/gpu/drm/panthor/panthor_drv.h
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_device.c b/drivers/gpu/drm/panthor/panthor_device.c
> index 81df49880bd8..4f254b574287 100644
> --- a/drivers/gpu/drm/panthor/panthor_device.c
> +++ b/drivers/gpu/drm/panthor/panthor_device.c
> @@ -17,6 +17,7 @@
>  #include "panthor_devfreq.h"
>  #include "panthor_device.h"
>  #include "panthor_fw.h"
> +#include "panthor_gem.h"
>  #include "panthor_gpu.h"
>  #include "panthor_hw.h"
>  #include "panthor_mmu.h"
> @@ -98,6 +99,7 @@ void panthor_device_unplug(struct panthor_device *ptdev)
>  	/* Now, try to cleanly shutdown the GPU before the device resources
>  	 * get reclaimed.
>  	 */
> +	panthor_gem_fini(ptdev);
>  	panthor_sched_unplug(ptdev);
>  	panthor_fw_unplug(ptdev);
>  	panthor_mmu_unplug(ptdev);
> @@ -269,6 +271,8 @@ int panthor_device_init(struct panthor_device *ptdev)
>  	if (ret)
>  		goto err_unplug_fw;
>  
> +	panthor_gem_init(ptdev);
> +
>  	/* ~3 frames */
>  	pm_runtime_set_autosuspend_delay(ptdev->base.dev, 50);
>  	pm_runtime_use_autosuspend(ptdev->base.dev);
> diff --git a/drivers/gpu/drm/panthor/panthor_device.h b/drivers/gpu/drm/panthor/panthor_device.h
> index 4fc7cf2aeed5..54ca61567426 100644
> --- a/drivers/gpu/drm/panthor/panthor_device.h
> +++ b/drivers/gpu/drm/panthor/panthor_device.h
> @@ -135,6 +135,9 @@ struct panthor_device {
>  	/** @devfreq: Device frequency scaling management data. */
>  	struct panthor_devfreq *devfreq;
>  
> +	/** @huge_mnt: tmpfs mount point with Transparent Hugepage enabled. */
> +	struct vfsmount *huge_mnt;

Now that we have a helper to create a huge mountpoint, wouldn't it
make sense to have this field in drm_device instead of having each
driver add a huge_mnt field to their <driver>_device object.

> +
>  	/** @unplug: Device unplug related fields. */
>  	struct {
>  		/** @lock: Lock used to serialize unplug operations. */
> diff --git a/drivers/gpu/drm/panthor/panthor_drv.c b/drivers/gpu/drm/panthor/panthor_drv.c
> index fdbe89ef7f43..a2be3b904ca2 100644
> --- a/drivers/gpu/drm/panthor/panthor_drv.c
> +++ b/drivers/gpu/drm/panthor/panthor_drv.c
> @@ -1556,6 +1556,7 @@ static const struct file_operations panthor_drm_driver_fops = {
>  	.read = drm_read,
>  	.llseek = noop_llseek,
>  	.mmap = panthor_mmap,
> +	.get_unmapped_area = drm_gem_get_unmapped_area,
>  	.show_fdinfo = drm_show_fdinfo,
>  	.fop_flags = FOP_UNSIGNED_OFFSET,
>  };
> @@ -1623,6 +1624,12 @@ static const struct drm_driver panthor_drm_driver = {
>  #endif
>  };
>  
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +bool panthor_transparent_hugepage;
> +module_param_named(transparent_hugepage, panthor_transparent_hugepage, bool, 0400);
> +MODULE_PARM_DESC(transparent_hugepage, "Use a dedicated tmpfs mount point with Transparent Hugepage enabled (false = default)");
> +#endif
> +
>  static int panthor_probe(struct platform_device *pdev)
>  {
>  	struct panthor_device *ptdev;
> diff --git a/drivers/gpu/drm/panthor/panthor_drv.h b/drivers/gpu/drm/panthor/panthor_drv.h
> new file mode 100644
> index 000000000000..27fe9b6f77bd
> --- /dev/null
> +++ b/drivers/gpu/drm/panthor/panthor_drv.h
> @@ -0,0 +1,11 @@
> +// SPDX-License-Identifier: GPL-2.0 or MIT
> +/* Copyright 2025 Amazon.com, Inc. or its affiliates */
> +
> +#ifndef __PANTHOR_DRV_H__
> +#define __PANTHOR_DRV_H__
> +
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +extern bool panthor_transparent_hugepage;
> +#endif
> +
> +#endif
> diff --git a/drivers/gpu/drm/panthor/panthor_gem.c b/drivers/gpu/drm/panthor/panthor_gem.c
> index 156c7a0b62a2..16916e0b6d89 100644
> --- a/drivers/gpu/drm/panthor/panthor_gem.c
> +++ b/drivers/gpu/drm/panthor/panthor_gem.c
> @@ -1,6 +1,7 @@
>  // SPDX-License-Identifier: GPL-2.0 or MIT
>  /* Copyright 2019 Linaro, Ltd, Rob Herring <robh@kernel.org> */
>  /* Copyright 2023 Collabora ltd. */
> +/* Copyright 2025 Amazon.com, Inc. or its affiliates */
>  
>  #include <linux/cleanup.h>
>  #include <linux/dma-buf.h>
> @@ -11,10 +12,35 @@
>  #include <drm/panthor_drm.h>
>  
>  #include "panthor_device.h"
> +#include "panthor_drv.h"
>  #include "panthor_fw.h"
>  #include "panthor_gem.h"
>  #include "panthor_mmu.h"
>  
> +void panthor_gem_init(struct panthor_device *ptdev)
> +{
> +	struct vfsmount *huge_mnt;
> +
> +	if (!panthor_transparent_hugepage)
> +		return;
> +
> +	huge_mnt = drm_gem_shmem_huge_mnt_create("within_size");
> +	if (IS_ERR(huge_mnt)) {
> +		drm_warn(&ptdev->base, "Can't use Transparent Hugepage (%ld)\n",
> +			 PTR_ERR(huge_mnt));
> +		return;
> +	}
> +
> +	ptdev->huge_mnt = huge_mnt;
> +
> +	drm_info(&ptdev->base, "Using Transparent Hugepage\n");
> +}
> +
> +void panthor_gem_fini(struct panthor_device *ptdev)
> +{
> +	drm_gem_shmem_huge_mnt_free(ptdev->huge_mnt);
> +}
> +
>  #ifdef CONFIG_DEBUG_FS
>  static void panthor_gem_debugfs_bo_init(struct panthor_gem_object *bo)
>  {
> @@ -270,10 +296,12 @@ panthor_gem_create_with_handle(struct drm_file *file,
>  			       u64 *size, u32 flags, u32 *handle)
>  {
>  	int ret;
> +	struct panthor_device *ptdev =
> +		container_of(ddev, struct panthor_device, base);
>  	struct drm_gem_shmem_object *shmem;
>  	struct panthor_gem_object *bo;
>  
> -	shmem = drm_gem_shmem_create(ddev, *size);
> +	shmem = drm_gem_shmem_create_with_mnt(ddev, *size, ptdev->huge_mnt);
>  	if (IS_ERR(shmem))
>  		return PTR_ERR(shmem);
>  
> diff --git a/drivers/gpu/drm/panthor/panthor_gem.h b/drivers/gpu/drm/panthor/panthor_gem.h
> index 80c6e24112d0..6804b3912cc2 100644
> --- a/drivers/gpu/drm/panthor/panthor_gem.h
> +++ b/drivers/gpu/drm/panthor/panthor_gem.h
> @@ -136,6 +136,9 @@ struct panthor_gem_object *to_panthor_bo(struct drm_gem_object *obj)
>  	return container_of(to_drm_gem_shmem_obj(obj), struct panthor_gem_object, base);
>  }
>  
> +void panthor_gem_init(struct panthor_device *ptdev);
> +void panthor_gem_fini(struct panthor_device *ptdev);
> +
>  struct drm_gem_object *panthor_gem_create_object(struct drm_device *ddev, size_t size);
>  
>  int

On 30/09/2025 12:34, Boris Brezillon wrote:
> On Mon, 29 Sep 2025 22:03:14 +0200
> Loïc Molinari <loic.molinari@collabora.com> wrote:
> 
>> diff --git a/drivers/gpu/drm/panthor/panthor_device.h b/drivers/gpu/drm/panthor/panthor_device.h
>> index 4fc7cf2aeed5..54ca61567426 100644
>> --- a/drivers/gpu/drm/panthor/panthor_device.h
>> +++ b/drivers/gpu/drm/panthor/panthor_device.h
>> @@ -135,6 +135,9 @@ struct panthor_device {
>>   	/** @devfreq: Device frequency scaling management data. */
>>   	struct panthor_devfreq *devfreq;
>>   
>> +	/** @huge_mnt: tmpfs mount point with Transparent Hugepage enabled. */
>> +	struct vfsmount *huge_mnt;
> 
> Now that we have a helper to create a huge mountpoint, wouldn't it
> make sense to have this field in drm_device instead of having each
> driver add a huge_mnt field to their <driver>_device object.

Not sure this should be enforced for all DRM drivers since most of them 
don't create separate huge mountpoints (only 4 for now including this 
patchset) and I guess some maintainers might prefer to depend on the 
sysfs interace to enable huge pages.

>> +
>>   	/** @unplug: Device unplug related fields. */
>>   	struct {
>>   		/** @lock: Lock used to serialize unplug operations. */
> 

Loïc

On Tue, 30 Sep 2025 18:31:11 +0200
Loïc Molinari <loic.molinari@collabora.com> wrote:

> On 30/09/2025 12:34, Boris Brezillon wrote:
> > On Mon, 29 Sep 2025 22:03:14 +0200
> > Loïc Molinari <loic.molinari@collabora.com> wrote:
> >   
> >> diff --git a/drivers/gpu/drm/panthor/panthor_device.h b/drivers/gpu/drm/panthor/panthor_device.h
> >> index 4fc7cf2aeed5..54ca61567426 100644
> >> --- a/drivers/gpu/drm/panthor/panthor_device.h
> >> +++ b/drivers/gpu/drm/panthor/panthor_device.h
> >> @@ -135,6 +135,9 @@ struct panthor_device {
> >>   	/** @devfreq: Device frequency scaling management data. */
> >>   	struct panthor_devfreq *devfreq;
> >>   
> >> +	/** @huge_mnt: tmpfs mount point with Transparent Hugepage enabled. */
> >> +	struct vfsmount *huge_mnt;  
> > 
> > Now that we have a helper to create a huge mountpoint, wouldn't it
> > make sense to have this field in drm_device instead of having each
> > driver add a huge_mnt field to their <driver>_device object.  
> 
> Not sure this should be enforced for all DRM drivers since most of them 
> don't create separate huge mountpoints (only 4 for now including this 
> patchset) and I guess some maintainers might prefer to depend on the 
> sysfs interace to enable huge pages.

I'm not saying we should create the huge mountpoint by default, but if
this is a generic helper, it makes sense to also manage this mountpoint
internally. In the end, it'd be a small price to pay for drivers that
don't need it (the size of a pointer in the drm_device object), and
with this in place, driver wouldn't even have to call
drm_gem_shmem_huge_mnt_free() manually (can be automated with a
drmm_add_action_or_reset() calling kern_unmount() inside
drm_gem_shmem_huge_mnt_create()).

> 
> >> +
> >>   	/** @unplug: Device unplug related fields. */
> >>   	struct {
> >>   		/** @lock: Lock used to serialize unplug operations. */  
> >   
> 
> Loïc