Re: [PATCH v3 3/3] drm/xe: Block exec and rebind worker while evicting for suspend / hibernate

[Matthew Auld <matthew.auld@intel.com>]

On 04/09/2025 14:06, Thomas Hellström wrote:
> When the xe pm_notifier evicts for suspend / hibernate, there might be
> racing tasks trying to re-validate again. This can lead to suspend taking
> excessive time or get stuck in a live-lock. This behaviour becomes
> much worse with the fix that actually makes re-validation bring back
> bos to VRAM rather than letting them remain in TT.
> 
> Prevent that by having exec and the rebind worker waiting for a completion
> that is set to block by the pm_notifier before suspend and is signaled
> by the pm_notifier after resume / wakeup.
> 
> It's probably still possible to craft malicious applications that block
> suspending. More work is pending to fix that.
> 
> v3:
> - Avoid wait_for_completion() in the kernel worker since it could
>    potentially cause work item flushes from freezable processes to
>    wait forever. Instead terminate the rebind workers if needed and
>    re-launch at resume. (Matt Auld)
> 
> Link: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/4288
> Fixes: c6a4d46ec1d7 ("drm/xe: evict user memory in PM notifier")
> Cc: Matthew Auld <matthew.auld@intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: <stable@vger.kernel.org> # v6.16+
> Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> ---
>   drivers/gpu/drm/xe/xe_device_types.h |  6 ++++
>   drivers/gpu/drm/xe/xe_exec.c         |  9 ++++++
>   drivers/gpu/drm/xe/xe_pm.c           | 20 ++++++++++++
>   drivers/gpu/drm/xe/xe_vm.c           | 46 +++++++++++++++++++++++++++-
>   drivers/gpu/drm/xe/xe_vm.h           |  2 ++
>   drivers/gpu/drm/xe/xe_vm_types.h     |  5 +++
>   6 files changed, 87 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_device_types.h b/drivers/gpu/drm/xe/xe_device_types.h
> index 092004d14db2..1e780f8a2a8c 100644
> --- a/drivers/gpu/drm/xe/xe_device_types.h
> +++ b/drivers/gpu/drm/xe/xe_device_types.h
> @@ -507,6 +507,12 @@ struct xe_device {
>   
>   	/** @pm_notifier: Our PM notifier to perform actions in response to various PM events. */
>   	struct notifier_block pm_notifier;
> +	/** @pm_block: Completion to block validating tasks on suspend / hibernate prepare */
> +	struct completion pm_block;
> +	/** @rebind_resume_list: List of wq items to kick on resume. */
> +	struct list_head rebind_resume_list;
> +	/** @rebind_resume_lock: Lock to protect the rebind_resume_list */
> +	struct mutex rebind_resume_lock;
>   
>   	/** @pmt: Support the PMT driver callback interface */
>   	struct {
> diff --git a/drivers/gpu/drm/xe/xe_exec.c b/drivers/gpu/drm/xe/xe_exec.c
> index 44364c042ad7..374c831e691b 100644
> --- a/drivers/gpu/drm/xe/xe_exec.c
> +++ b/drivers/gpu/drm/xe/xe_exec.c
> @@ -237,6 +237,15 @@ int xe_exec_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
>   		goto err_unlock_list;
>   	}
>   
> +	/*
> +	 * It's OK to block interruptible here with the vm lock held, since
> +	 * on task freezing during suspend / hibernate, the call will
> +	 * return -ERESTARTSYS and the IOCTL will be rerun.
> +	 */
> +	err = wait_for_completion_interruptible(&xe->pm_block);
> +	if (err)
> +		goto err_unlock_list;
> +
>   	vm_exec.vm = &vm->gpuvm;
>   	vm_exec.flags = DRM_EXEC_INTERRUPTIBLE_WAIT;
>   	if (xe_vm_in_lr_mode(vm)) {
> diff --git a/drivers/gpu/drm/xe/xe_pm.c b/drivers/gpu/drm/xe/xe_pm.c
> index bee9aacd82e7..6d59990ff6ba 100644
> --- a/drivers/gpu/drm/xe/xe_pm.c
> +++ b/drivers/gpu/drm/xe/xe_pm.c
> @@ -297,6 +297,18 @@ static u32 vram_threshold_value(struct xe_device *xe)
>   	return DEFAULT_VRAM_THRESHOLD;
>   }
>   
> +static void xe_pm_wake_preempt_workers(struct xe_device *xe)
> +{
> +	struct list_head *link, *next;
> +
> +	mutex_lock(&xe->rebind_resume_lock);
> +	list_for_each_safe(link, next, &xe->rebind_resume_list) {
> +		list_del_init(link);
> +		xe_vm_resume_preempt_worker(link);
> +	}
> +	mutex_unlock(&xe->rebind_resume_lock);
> +}
> +
>   static int xe_pm_notifier_callback(struct notifier_block *nb,
>   				   unsigned long action, void *data)
>   {
> @@ -306,6 +318,7 @@ static int xe_pm_notifier_callback(struct notifier_block *nb,
>   	switch (action) {
>   	case PM_HIBERNATION_PREPARE:
>   	case PM_SUSPEND_PREPARE:
> +		reinit_completion(&xe->pm_block);
>   		xe_pm_runtime_get(xe);
>   		err = xe_bo_evict_all_user(xe);
>   		if (err)
> @@ -322,6 +335,8 @@ static int xe_pm_notifier_callback(struct notifier_block *nb,
>   		break;
>   	case PM_POST_HIBERNATION:
>   	case PM_POST_SUSPEND:
> +		complete_all(&xe->pm_block);
> +		xe_pm_wake_preempt_workers(xe);
>   		xe_bo_notifier_unprepare_all_pinned(xe);
>   		xe_pm_runtime_put(xe);
>   		break;
> @@ -348,6 +363,11 @@ int xe_pm_init(struct xe_device *xe)
>   	if (err)
>   		return err;
>   
> +	init_completion(&xe->pm_block);
> +	complete_all(&xe->pm_block);
> +	mutex_init(&xe->rebind_resume_lock);

err = drmm_mutex_init(&xe->rebind_resume_lock);

?

> +	INIT_LIST_HEAD(&xe->rebind_resume_list);
> +
>   	/* For now suspend/resume is only allowed with GuC */
>   	if (!xe_device_uc_enabled(xe))
>   		return 0;
> diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
> index f55f96bb240a..97aad1d53a8c 100644
> --- a/drivers/gpu/drm/xe/xe_vm.c
> +++ b/drivers/gpu/drm/xe/xe_vm.c
> @@ -394,6 +394,9 @@ static int xe_gpuvm_validate(struct drm_gpuvm_bo *vm_bo, struct drm_exec *exec)
>   		list_move_tail(&gpuva_to_vma(gpuva)->combined_links.rebind,
>   			       &vm->rebind_list);
>   
> +	if (!try_wait_for_completion(&vm->xe->pm_block))
> +		return -EAGAIN;
> +
>   	ret = xe_bo_validate(gem_to_xe_bo(vm_bo->obj), vm, false);
>   	if (ret)
>   		return ret;
> @@ -480,6 +483,37 @@ static int xe_preempt_work_begin(struct drm_exec *exec, struct xe_vm *vm,
>   	return xe_vm_validate_rebind(vm, exec, vm->preempt.num_exec_queues);
>   }
>   
> +static bool vm_suspend_preempt_worker(struct xe_vm *vm)
> +{
> +	struct xe_device *xe = vm->xe;
> +	bool ret = false;
> +
> +	mutex_lock(&xe->rebind_resume_lock);
> +	if (!try_wait_for_completion(&vm->xe->pm_block)) {
> +		ret = true;
> +		list_move_tail(&vm->preempt.pm_activate_link, &xe->rebind_resume_list);
> +	}
> +	pr_info("Suspending %p\n", vm);
> +	mutex_unlock(&xe->rebind_resume_lock);
> +
> +	return ret;
> +}
> +
> +/**
> + * xe_vm_resume_preempt_worker() - Resume the preempt worker.
> + * @vm: The vm whose preempt worker to resume.
> + *
> + * Resume a preempt worker that was previously suspended by
> + * vm_suspend_preempt_worker().
> + */
> +void xe_vm_resume_preempt_worker(struct list_head *link)

I guess should use vm arg here?

> +{
> +	struct xe_vm *vm = container_of(link, typeof(*vm), preempt.pm_activate_link);
> +
> +	pr_info("Resuming %p\n", vm);
> +	queue_work(vm->xe->ordered_wq, &vm->preempt.rebind_work);
> +}
> +
>   static void preempt_rebind_work_func(struct work_struct *w)
>   {
>   	struct xe_vm *vm = container_of(w, struct xe_vm, preempt.rebind_work);
> @@ -503,6 +537,11 @@ static void preempt_rebind_work_func(struct work_struct *w)
>   	}
>   
>   retry:
> +	if (!try_wait_for_completion(&vm->xe->)) && vm_suspend_preempt_worker(vm)) {
> +		up_write(&vm->lock);
> +		return;
> +	}
> +
>   	if (xe_vm_userptr_check_repin(vm)) {
>   		err = xe_vm_userptr_pin(vm);
>   		if (err)
> @@ -1741,6 +1780,7 @@ struct xe_vm *xe_vm_create(struct xe_device *xe, u32 flags, struct xe_file *xef)
>   	if (flags & XE_VM_FLAG_LR_MODE) {
>   		INIT_WORK(&vm->preempt.rebind_work, preempt_rebind_work_func);
>   		xe_pm_runtime_get_noresume(xe);
> +		INIT_LIST_HEAD(&vm->preempt.pm_activate_link);
>   	}
>   
>   	if (flags & XE_VM_FLAG_FAULT_MODE) {
> @@ -1922,8 +1962,12 @@ void xe_vm_close_and_put(struct xe_vm *vm)
>   	xe_assert(xe, !vm->preempt.num_exec_queues);
>   
>   	xe_vm_close(vm);
> -	if (xe_vm_in_preempt_fence_mode(vm))
> +	if (xe_vm_in_preempt_fence_mode(vm)) {
> +		mutex_lock(&xe->rebind_resume_lock);
> +		list_del_init(&vm->preempt.pm_activate_link);
> +		mutex_unlock(&xe->rebind_resume_lock);
>   		flush_work(&vm->preempt.rebind_work);
> +	}
>   	if (xe_vm_in_fault_mode(vm))
>   		xe_svm_close(vm);
>   
> diff --git a/drivers/gpu/drm/xe/xe_vm.h b/drivers/gpu/drm/xe/xe_vm.h
> index b3e5bec0fa58..f2639794278b 100644
> --- a/drivers/gpu/drm/xe/xe_vm.h
> +++ b/drivers/gpu/drm/xe/xe_vm.h
> @@ -281,6 +281,8 @@ struct dma_fence *xe_vm_bind_kernel_bo(struct xe_vm *vm, struct xe_bo *bo,
>   				       struct xe_exec_queue *q, u64 addr,
>   				       enum xe_cache_level cache_lvl);
>   
> +void xe_vm_resume_preempt_worker(struct list_head *link);
> +
>   /**
>    * xe_vm_resv() - Return's the vm's reservation object
>    * @vm: The vm
> diff --git a/drivers/gpu/drm/xe/xe_vm_types.h b/drivers/gpu/drm/xe/xe_vm_types.h
> index b5108d010786..e1a786db5f89 100644
> --- a/drivers/gpu/drm/xe/xe_vm_types.h
> +++ b/drivers/gpu/drm/xe/xe_vm_types.h
> @@ -338,6 +338,11 @@ struct xe_vm {
>   		 * BOs
>   		 */
>   		struct work_struct rebind_work;
> +		/**
> +		 * @preempt.pm_activate_link: Link to list of rebind workers to be
> +		 * kicked on resume.
> +		 */
> +		struct list_head pm_activate_link;
>   	} preempt;
>   
>   	/** @um: unified memory state */