[PATCH 6.18 183/641] drm/panthor: Evict groups before VM termination

Greg Kroah-Hartman
2026-02-25T01:46:02Z

6.18-stable review patch. If anyone has any objections, please let me know.

------------------

From: Ketil Johnsen <ketil.johnsen@arm.com>

[ Upstream commit 565ed40b5fc1242f7538a016fce5a85f802d4fb5 ]

Ensure all related groups are evicted and suspended before VM
destruction takes place.

This fixes an issue where panthor_vm_destroy() destroys and unmaps the
heap context while there are still on slot groups using this.
The FW will do a write out to the heap context when a CSG (group) is
suspended, so a premature unmap of the heap context will cause a
GPU page fault.
This page fault is quite harmless, and do not affect the continued
operation of the GPU.

Fixes: 647810ec2476 ("drm/panthor: Add the MMU/VM logical block")
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Ketil Johnsen <ketil.johnsen@arm.com>
Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Link: https://patch.msgid.link/20251219093546.1227697-1-ketil.johnsen@arm.com
Co-developed-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/panthor/panthor_mmu.c | 4 ++++
drivers/gpu/drm/panthor/panthor_sched.c | 14 ++++++++++++++
drivers/gpu/drm/panthor/panthor_sched.h | 1 +
3 files changed, 19 insertions(+)

diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
index 15961629872e1..0fd8ffec92dd0 100644
--- a/drivers/gpu/drm/panthor/panthor_mmu.c
+++ b/drivers/gpu/drm/panthor/panthor_mmu.c
@@ -1561,6 +1561,10 @@ static void panthor_vm_destroy(struct panthor_vm *vm)

vm->destroyed = true;

+ /* Tell scheduler to stop all GPU work related to this VM */
+ if (refcount_read(&vm->as.active_cnt) > 0)
+ panthor_sched_prepare_for_vm_destruction(vm->ptdev);
+
mutex_lock(&vm->heaps.lock);
panthor_heap_pool_destroy(vm->heaps.pool);
vm->heaps.pool = NULL;
diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
index 8f11fe73bee23..c7dd98936bd6b 100644
--- a/drivers/gpu/drm/panthor/panthor_sched.c
+++ b/drivers/gpu/drm/panthor/panthor_sched.c
@@ -2707,6 +2707,20 @@ void panthor_sched_report_mmu_fault(struct panthor_device *ptdev)
panthor_sched_immediate_tick(ptdev);
}

+void panthor_sched_prepare_for_vm_destruction(struct panthor_device *ptdev)
+{
+ /* FW can write out internal state, like the heap context, during CSG
+ * suspend. It is therefore important that the scheduler has fully
+ * evicted any pending and related groups before VM destruction can
+ * safely continue. Failure to do so can lead to GPU page faults.
+ * A controlled termination of a Panthor instance involves destroying
+ * the group(s) before the VM. This means any relevant group eviction
+ * has already been initiated by this point, and we just need to
+ * ensure that any pending tick_work() has been completed.
+ */
+ flush_work(&ptdev->scheduler->tick_work.work);
+}
+
void panthor_sched_resume(struct panthor_device *ptdev)
{
/* Force a tick to re-evaluate after a resume. */
diff --git a/drivers/gpu/drm/panthor/panthor_sched.h b/drivers/gpu/drm/panthor/panthor_sched.h
index 742b0b4ff3a3c..6a560ab0a5b31 100644
--- a/drivers/gpu/drm/panthor/panthor_sched.h
+++ b/drivers/gpu/drm/panthor/panthor_sched.h
@@ -49,6 +49,7 @@ void panthor_sched_suspend(struct panthor_device *ptdev);
void panthor_sched_resume(struct panthor_device *ptdev);

void panthor_sched_report_mmu_fault(struct panthor_device *ptdev);
+void panthor_sched_prepare_for_vm_destruction(struct panthor_device *ptdev);
void panthor_sched_report_fw_events(struct panthor_device *ptdev, u32 events);

void panthor_fdinfo_gather_group_samples(struct panthor_file *pfile);
--
2.51.0