linux-kernel - [PATCH] drm/panthor: Avoid adding of kernel BOs to extobj list

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20251113184544.1832461-1-akash.goel@arm.com>
Date: Thu, 13 Nov 2025 18:45:44 +0000
From: Akash Goel <akash.goel@....com>
To: boris.brezillon@...labora.com,
	liviu.dudau@....com,
	steven.price@....com
Cc: dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org,
	maarten.lankhorst@...ux.intel.com,
	mripard@...nel.org,
	tzimmermann@...e.de,
	airlied@...il.com,
	daniel@...ll.ch,
	nd@....com,
	Akash Goel <akash.goel@....com>
Subject: [PATCH] drm/panthor: Avoid adding of kernel BOs to extobj list

The kernel BOs unnecessarily got added to the external objects list
of drm_gpuvm, when mapping to GPU, which would have resulted in few
extra CPU cycles being spent at the time of job submission as
drm_exec_until_all_locked() loop iterates over all external objects.

Kernel BOs are private to a VM and so they share the dma_resv object of
the dummy GEM object created for a VM. Use of DRM_EXEC_IGNORE_DUPLICATES
flag ensured the recursive locking of the dummy GEM object was ignored.
Also no extra space got allocated to add fences to the dma_resv object
of dummy GEM object. So no other impact apart from few extra CPU cycles.

This commit sets the pointer to dma_resv object of GEM object of
kernel BOs before they are mapped to GPU, to prevent them from
being added to external objects list.

Signed-off-by: Akash Goel <akash.goel@....com>
---
 drivers/gpu/drm/panthor/panthor_gem.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/panthor/panthor_gem.c b/drivers/gpu/drm/panthor/panthor_gem.c
index f369cc3e2a5f..10d255cccc09 100644
--- a/drivers/gpu/drm/panthor/panthor_gem.c
+++ b/drivers/gpu/drm/panthor/panthor_gem.c
@@ -145,6 +145,9 @@ panthor_kernel_bo_create(struct panthor_device *ptdev, struct panthor_vm *vm,
 	bo = to_panthor_bo(&obj->base);
 	kbo->obj = &obj->base;
 	bo->flags = bo_flags;
+	bo->exclusive_vm_root_gem = panthor_vm_root_gem(vm);
+	drm_gem_object_get(bo->exclusive_vm_root_gem);
+	bo->base.base.resv = bo->exclusive_vm_root_gem->resv;

 	if (vm == panthor_fw_vm(ptdev))
 		debug_flags |= PANTHOR_DEBUGFS_GEM_USAGE_FLAG_FW_MAPPED;
@@ -168,9 +171,6 @@ panthor_kernel_bo_create(struct panthor_device *ptdev, struct panthor_vm *vm,
 		goto err_free_va;

 	kbo->vm = panthor_vm_get(vm);
-	bo->exclusive_vm_root_gem = panthor_vm_root_gem(vm);
-	drm_gem_object_get(bo->exclusive_vm_root_gem);
-	bo->base.base.resv = bo->exclusive_vm_root_gem->resv;
 	return kbo;

 err_free_va:
-- 
2.25.1