Re: [PATCH v4 15/18] drm/panthor: Track user owned VMs

[Adrian Larumbe]

Reviewed-by: Adrián Larumbe <adrian.larumbe@xxxxxxxxxxxxx>

On 26.08.2026 16:56, Boris Brezillon wrote:
> We will soon need this to fix the unplug logic and make sure panthor_vm
> objects are not left behind after an unplug.
> 
> Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/panthor/panthor_mmu.c | 31 +++++++++++++++++++++++++++----
>  1 file changed, 27 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
> index 47c57b39bd12..6368bf57b8f5 100644
> --- a/drivers/gpu/drm/panthor/panthor_mmu.c
> +++ b/drivers/gpu/drm/panthor/panthor_mmu.c
> @@ -117,12 +117,15 @@ struct panthor_mmu {
>  
>  	/** @vm: VMs management fields */
>  	struct {
> -		/** @vm.lock: Lock protecting access to list. */
> +		/** @vm.lock: Lock protecting access to list and user_owned. */
>  		struct mutex lock;
>  
>  		/** @vm.list: List containing all VMs. */
>  		struct list_head list;
>  
> +		/** @vm.list: List containing VMs with a valid handle. */
> +		struct list_head user_owned;
> +
>  		/** @vm.reset_in_progress: True if a reset is in progress. */
>  		bool reset_in_progress;
>  
> @@ -447,6 +450,9 @@ struct panthor_vm {
>  	/** @node: Used to insert the VM in the panthor_mmu::vm::list. */
>  	struct list_head node;
>  
> +	/* @user_node: Used to insert the VM in the panthor_mmu::vm::user_owned list. */
> +	struct list_head user_node;
> +
>  	/** @for_mcu: True if this is the MCU VM. */
>  	bool for_mcu;
>  
> @@ -1681,10 +1687,19 @@ int panthor_vm_pool_create_vm(struct panthor_device *ptdev,
>  	drm_gem_object_get(&pool->dummy->base);
>  	vm->dummy = pool->dummy;
>  
> +	/* Insert in the list before xa_alloc() so we can't race with
> +	 * panthor_vm_pool_destroy_vm() have the VM inserted in the
> +	 * user_owned list after it's been destroyed.
> +	 */
> +	scoped_guard(mutex, &ptdev->mmu->vm.lock)
> +		list_add_tail(&vm->user_node, &ptdev->mmu->vm.user_owned);
> +
>  	ret = xa_alloc(&pool->xa, &id, vm,
>  		       XA_LIMIT(1, PANTHOR_MAX_VMS_PER_FILE), GFP_KERNEL);
>  
>  	if (ret) {
> +		scoped_guard(mutex, &ptdev->mmu->vm.lock)
> +			list_del_init(&vm->user_node);
>  		panthor_vm_put(vm);
>  		return ret;
>  	}
> @@ -1739,13 +1754,19 @@ static void panthor_vm_destroy(struct panthor_vm *vm)
>   */
>  int panthor_vm_pool_destroy_vm(struct panthor_vm_pool *pool, u32 handle)
>  {
> +	struct panthor_device *ptdev;
>  	struct panthor_vm *vm;
>  
>  	vm = xa_erase(&pool->xa, handle);
> +	if (!vm)
> +		return -EINVAL;
> +
> +	ptdev = container_of(vm->as->base.drm, struct panthor_device, base);
> +	scoped_guard(mutex, &ptdev->mmu->vm.lock)
> +		list_del_init(&vm->user_node);
>  
>  	panthor_vm_destroy(vm);
> -
> -	return vm ? 0 : -EINVAL;
> +	return 0;
>  }
>  
>  /**
> @@ -1785,7 +1806,7 @@ void panthor_vm_pool_destroy(struct panthor_file *pfile)
>  		return;
>  
>  	xa_for_each(&pfile->vms->xa, i, vm)
> -		panthor_vm_destroy(vm);
> +		panthor_vm_pool_destroy_vm(pfile->vms, i);
>  
>  	if (pfile->vms->dummy)
>  		drm_gem_object_put(&pfile->vms->dummy->base);
> @@ -3182,6 +3203,7 @@ panthor_vm_create(struct panthor_device *ptdev, bool for_mcu,
>  		goto err_put_as;
>  	}
>  
> +	INIT_LIST_HEAD(&vm->user_node);
>  	vm->user_va_range = kernel_va_start;
>  	vm->as = as;
>  	mutex_init(&vm->heaps.lock);
> @@ -3707,6 +3729,7 @@ int panthor_mmu_init(struct panthor_device *ptdev)
>  		return ret;
>  
>  	INIT_LIST_HEAD(&mmu->vm.list);
> +	INIT_LIST_HEAD(&mmu->vm.user_owned);
>  	ret = drmm_mutex_init(&ptdev->base, &mmu->vm.lock);
>  	if (ret)
>  		return ret;
> 
> -- 
> 2.55.0


Adrian Larumbe