Re: [PATCH] drm/xe: Bump LRU for external objects on exec and rebind

[Matthew Brost <matthew.brost@intel.com>]

On Mon, Oct 12, 2026 at 03:26:07PM +0200, Thomas Hellström wrote:

Yikes, not sure how we missed this one and this is certainly not the
intent and will be large issue for compositor buffers.

I'd honestly lean towards this being a fixes.  

> The VM's private BOs get their LRU position refreshed in bulk via
> ttm_lru_bulk_move_tail() on vm->lru_bulk_move, both after a successful
> non-LR exec and after the LR preempt-fence rebind worker runs. External
> objects (BOs potentially shared across VMs) are never added to that
> per-VM bulk move list, so their LRU position is never refreshed by
> either path. This makes external objects in active use look more
> evictable than they are.
> 
> Add xe_vm_bump_lru(), which, under a single lru_lock critical section,
> performs the bulk move of the VM's private BOs and bumps each external
> object locked by the drm_exec transaction. Use it from both the non-LR
> exec path and the LR rebind worker, replacing the open-coded bulk move.
> 
> Cc: Matthew Auld <matthew.auld@intel.com>
> Cc: Matthew Brost <matthew.brost@intel.com>

Consider the above:
Reviewed-by: Matthew Brost <matthew.brost@intel.com>

> Assisted-by: LLM
> Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> ---
>  drivers/gpu/drm/xe/xe_exec.c |  7 ++-----
>  drivers/gpu/drm/xe/xe_vm.c   | 31 ++++++++++++++++++++++++++++---
>  drivers/gpu/drm/xe/xe_vm.h   |  2 ++
>  3 files changed, 32 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_exec.c b/drivers/gpu/drm/xe/xe_exec.c
> index d5293bc33a67..7dc9a0a1f569 100644
> --- a/drivers/gpu/drm/xe/xe_exec.c
> +++ b/drivers/gpu/drm/xe/xe_exec.c
> @@ -346,11 +346,8 @@ int xe_exec_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
>  	xe_sched_job_push(job);
>  	xe_vm_reactivate_rebind(vm);
>  
> -	if (!err && !xe_vm_in_lr_mode(vm)) {
> -		spin_lock(&xe->ttm.lru_lock);
> -		ttm_lru_bulk_move_tail(&vm->lru_bulk_move);
> -		spin_unlock(&xe->ttm.lru_lock);
> -	}
> +	if (!err && !xe_vm_in_lr_mode(vm))
> +		xe_vm_bump_lru(vm, exec);
>  
>  	if (mode == EXEC_MODE_LR)
>  		xe_hw_engine_group_resume_faulting_lr_jobs(group);
> diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
> index ef369df4aa26..095f762bbb6f 100644
> --- a/drivers/gpu/drm/xe/xe_vm.c
> +++ b/drivers/gpu/drm/xe/xe_vm.c
> @@ -413,6 +413,33 @@ int xe_vm_validate_rebind(struct xe_vm *vm, struct drm_exec *exec,
>  	return 0;
>  }
>  
> +/**
> + * xe_vm_bump_lru() - Bump the LRU position of BOs used by a submission
> + * @vm: The vm for which we are bumping LRUs.
> + * @exec: The struct drm_exec with the locked GEM objects.
> + *
> + * Move the VM's private BOs, and all external objects locked by @exec,
> + * to the LRU tail. Private BOs are moved in bulk using @vm's
> + * &xe_vm.lru_bulk_move. External objects, which may be shared with other
> + * VMs, are not part of that bulk move and are bumped individually.
> + */
> +void xe_vm_bump_lru(struct xe_vm *vm, struct drm_exec *exec)
> +{
> +	spinlock_t *lru_lock = &vm->xe->ttm.lru_lock;
> +	struct drm_gem_object *obj;
> +
> +	spin_lock(lru_lock);
> +	ttm_lru_bulk_move_tail(&vm->lru_bulk_move);
> +	drm_exec_for_each_locked_object(exec, obj) {
> +		if (!drm_gpuvm_is_extobj(&vm->gpuvm, obj))
> +			continue;
> +
> +		ttm_bo_move_to_lru_tail(&gem_to_xe_bo(obj)->ttm);
> +		cond_resched_lock(lru_lock);
> +	}
> +	spin_unlock(lru_lock);
> +}
> +
>  static int xe_preempt_work_begin(struct drm_exec *exec, struct xe_vm *vm,
>  				 bool *done)
>  {
> @@ -563,9 +590,7 @@ static void preempt_rebind_work_func(struct work_struct *w)
>  
>  #undef retry_required
>  
> -	spin_lock(&vm->xe->ttm.lru_lock);
> -	ttm_lru_bulk_move_tail(&vm->lru_bulk_move);
> -	spin_unlock(&vm->xe->ttm.lru_lock);
> +	xe_vm_bump_lru(vm, &exec);
>  
>  	/* Point of no return. */
>  	arm_preempt_fences(vm, &preempt_fences);
> diff --git a/drivers/gpu/drm/xe/xe_vm.h b/drivers/gpu/drm/xe/xe_vm.h
> index 89c4f95984a2..06138c3c4315 100644
> --- a/drivers/gpu/drm/xe/xe_vm.h
> +++ b/drivers/gpu/drm/xe/xe_vm.h
> @@ -284,6 +284,8 @@ int xe_vm_lock_vma(struct drm_exec *exec, struct xe_vma *vma);
>  int xe_vm_validate_rebind(struct xe_vm *vm, struct drm_exec *exec,
>  			  unsigned int num_fences);
>  
> +void xe_vm_bump_lru(struct xe_vm *vm, struct drm_exec *exec);
> +
>  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);
> -- 
> 2.56.0
>