Re: [PATCH v5 9/9] drm/panthor: Add a GEM shrinker

["Adrián Larumbe" <adrian.larumbe@collabora.com>]

Hi, seems that I have more questions about this patch.

On 09.03.2026 16:11, Boris Brezillon wrote:
> From: Akash Goel <akash.goel@arm.com>
>
> This implementation is losely based on the MSM shrinker, and it's
> relying on the drm_gpuvm eviction/validation infrastructure.
>
> Right now we only support swapout/eviction, but we could add an extra
> flag to specify when buffer content doesn't need to be preserved to
> avoid the swapout/swapin dance.
>
> Locking is a bit of a nightmare, but using _trylock() all the way in
> the reclaim path seems to make lockdep happy. And yes, we might be
> missing opportunities to reclaim when the system is under heavy GPU
> load/heavy memory pressure/heavy GPU VM activity, but that's better
> than no reclaim at all.
>
> v2:
> - Move gpu_mapped_shared next to the mmapped LRU
> - Add a bunch of missing is_[vm_bo,vma]_evicted() tests
> - Only test mmap_count to check if a BO is mmaped
> - Remove stale comment about shrinker not being a thing
> - Allow pin_count to be non-zero in panthor_gem_swapin_locked()
> - Fix panthor_gem_sync() to check for BO residency before doing the CPU sync
> - Fix the value returned by panthor_gem_shrinker_count() in case some
>   memory has been released
> - Check drmm_mutex_init() ret code
> - Explicitly mention that PANTHOR_GEM_UNRECLAIMABLE is the initial state
>   of all BOs
>
> v3:
> - Make panthor_gem_try_evict() static
> - Collect {A,R}-bs
>
> v4:
> - Update the reclaim_state in panthor_gem_mmap()
> - Don't reclaim GPU-mapped BOs if can_block() returns false
> - Skip evicited vm_bos in panthor_vm_update_bo_reclaim_lru_locked() to
>   avoid spurious WARN_ON()s
> - Explain why we have to do this
>   select_evicted_vma/repopulate_evicted_vma dance
>
> v5:
> - Properly report the reclaimable size in panthor_gem_debugfs_print_bos()
> - Check panthor_vm_lock_region() errors in
>   panthor_vm_evict_bo_mappings_locked()
> - Fix lock order inversion (dma_resv_wait_timeout() inside gpuva.lock)
>
> Signed-off-by: Akash Goel <akash.goel@arm.com>
> Co-developed-by: Boris Brezillon <boris.brezillon@collabora.com>
> Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
> Acked-by: Liviu Dudau <liviu.dudau@arm.com>
> Reviewed-by: Steven Price <steven.price@arm.com>
> ---
>  drivers/gpu/drm/panthor/panthor_device.c |  11 +-
>  drivers/gpu/drm/panthor/panthor_device.h |  73 ++++
>  drivers/gpu/drm/panthor/panthor_gem.c    | 468 ++++++++++++++++++++++-
>  drivers/gpu/drm/panthor/panthor_gem.h    |  68 ++++
>  drivers/gpu/drm/panthor/panthor_mmu.c    | 359 ++++++++++++++++-
>  drivers/gpu/drm/panthor/panthor_mmu.h    |   8 +
>  6 files changed, 960 insertions(+), 27 deletions(-)
>
> diff --git a/drivers/gpu/drm/panthor/panthor_device.c b/drivers/gpu/drm/panthor/panthor_device.c
> index 54fbb1aa07c5..bc62a498a8a8 100644
> --- a/drivers/gpu/drm/panthor/panthor_device.c
> +++ b/drivers/gpu/drm/panthor/panthor_device.c
> @@ -2,6 +2,7 @@
>  /* Copyright 2018 Marty E. Plummer <hanetzer@startmail.com> */
>  /* Copyright 2019 Linaro, Ltd, Rob Herring <robh@kernel.org> */
>  /* Copyright 2023 Collabora ltd. */
> +/* Copyright 2025 ARM Limited. All rights reserved. */
>
>  #include <linux/clk.h>
>  #include <linux/mm.h>
> @@ -122,6 +123,7 @@ void panthor_device_unplug(struct panthor_device *ptdev)
>  	panthor_sched_unplug(ptdev);
>  	panthor_fw_unplug(ptdev);
>  	panthor_mmu_unplug(ptdev);
> +	panthor_gem_shrinker_unplug(ptdev);
>  	panthor_gpu_unplug(ptdev);
>  	panthor_pwr_unplug(ptdev);
>
> @@ -291,10 +293,14 @@ int panthor_device_init(struct panthor_device *ptdev)
>  	if (ret)
>  		goto err_unplug_gpu;
>
> -	ret = panthor_mmu_init(ptdev);
> +	ret = panthor_gem_shrinker_init(ptdev);
>  	if (ret)
>  		goto err_unplug_gpu;
>
> +	ret = panthor_mmu_init(ptdev);
> +	if (ret)
> +		goto err_unplug_shrinker;
> +
>  	ret = panthor_fw_init(ptdev);
>  	if (ret)
>  		goto err_unplug_mmu;
> @@ -326,6 +332,9 @@ int panthor_device_init(struct panthor_device *ptdev)
>  err_unplug_mmu:
>  	panthor_mmu_unplug(ptdev);
>
> +err_unplug_shrinker:
> +	panthor_gem_shrinker_unplug(ptdev);
> +
>  err_unplug_gpu:
>  	panthor_gpu_unplug(ptdev);
>
> diff --git a/drivers/gpu/drm/panthor/panthor_device.h b/drivers/gpu/drm/panthor/panthor_device.h
> index b6696f73a536..5cba272f9b4d 100644
> --- a/drivers/gpu/drm/panthor/panthor_device.h
> +++ b/drivers/gpu/drm/panthor/panthor_device.h
> @@ -14,6 +14,7 @@
>  #include <linux/spinlock.h>
>
>  #include <drm/drm_device.h>
> +#include <drm/drm_gem.h>
>  #include <drm/drm_mm.h>
>  #include <drm/gpu_scheduler.h>
>  #include <drm/panthor_drm.h>
> @@ -178,6 +179,78 @@ struct panthor_device {
>  	/** @devfreq: Device frequency scaling management data. */
>  	struct panthor_devfreq *devfreq;
>
> +	/** @reclaim: Reclaim related stuff */
> +	struct {
> +		/** @reclaim.shrinker: Shrinker instance */
> +		struct shrinker *shrinker;
> +
> +		/** @reclaim.lock: Lock protecting all LRUs */
> +		struct mutex lock;
> +
> +		/**
> +		 * @reclaim.unused: BOs with unused pages
> +		 *
> +		 * Basically all buffers that got mmapped, vmapped or GPU mapped and
> +		 * then unmapped. There should be no contention on these buffers,
> +		 * making them ideal to reclaim.
> +		 */
> +		struct drm_gem_lru unused;
> +
> +		/**
> +		 * @reclaim.mmapped: mmap()-ed buffers
> +		 *
> +		 * Those are relatively easy to reclaim since we don't need user
> +		 * agreement, we can simply teardown the mapping and let it fault on
> +		 * the next access.
> +		 */
> +		struct drm_gem_lru mmapped;
> +
> +		/**
> +		 * @reclaim.gpu_mapped_shared: shared BO LRU list
> +		 *
> +		 * That's the most tricky BO type to reclaim, because it involves
> +		 * tearing down all mappings in all VMs where this BO is mapped,
> +		 * which increases the risk of contention and thus decreases the
> +		 * likeliness of success.
> +		 */
> +		struct drm_gem_lru gpu_mapped_shared;
> +
> +		/**
> +		 * @reclaim.vms: VM LRU list
> +		 *
> +		 * VMs that have reclaimable BOs only mapped to a single VM are placed
> +		 * in this LRU. Reclaiming such BOs implies waiting for VM idleness
> +		 * (no in-flight GPU jobs targeting this VM), meaning we can't reclaim
> +		 * those if we're in a context where we can't block/sleep.
> +		 */
> +		struct list_head vms;
> +
> +		/**
> +		 * @reclaim.gpu_mapped_count: Global counter of pages that are GPU mapped
> +		 *
> +		 * Allows us to get the number of reclaimable pages without walking
> +		 * the vms and gpu_mapped_shared LRUs.
> +		 */
> +		long gpu_mapped_count;
> +
> +		/**
> +		 * @reclaim.retry_count: Number of times we ran the shrinker without being
> +		 * able to reclaim stuff
> +		 *
> +		 * Used to stop scanning GEMs when too many attempts were made
> +		 * without progress.
> +		 */
> +		atomic_t retry_count;
> +
> +#ifdef CONFIG_DEBUG_FS
> +		/**
> +		 * @reclaim.nr_pages_reclaimed_on_last_scan: Number of pages reclaimed on the last
> +		 * shrinker scan
> +		 */
> +		unsigned long nr_pages_reclaimed_on_last_scan;
> +#endif
> +	} reclaim;
> +
>  	/** @unplug: Device unplug related fields. */
>  	struct {
>  		/** @lock: Lock used to serialize unplug operations. */
> diff --git a/drivers/gpu/drm/panthor/panthor_gem.c b/drivers/gpu/drm/panthor/panthor_gem.c
> index 7c127d908c6f..855ce378afce 100644
> --- a/drivers/gpu/drm/panthor/panthor_gem.c
> +++ b/drivers/gpu/drm/panthor/panthor_gem.c
> @@ -2,8 +2,10 @@
>  /* Copyright 2019 Linaro, Ltd, Rob Herring <robh@kernel.org> */
>  /* Copyright 2023 Collabora ltd. */
>  /* Copyright 2025 Amazon.com, Inc. or its affiliates */
> +/* Copyright 2025 ARM Limited. All rights reserved. */
>
>  #include <linux/cleanup.h>
> +#include <linux/debugfs.h>
>  #include <linux/dma-buf.h>
>  #include <linux/dma-mapping.h>
>  #include <linux/err.h>
> @@ -12,6 +14,8 @@
>
>  #include <drm/drm_debugfs.h>
>  #include <drm/drm_file.h>
> +#include <drm/drm_gpuvm.h>
> +#include <drm/drm_managed.h>
>  #include <drm/drm_prime.h>
>  #include <drm/drm_print.h>
>  #include <drm/panthor_drm.h>
> @@ -114,6 +118,103 @@ should_map_wc(struct panthor_gem_object *bo)
>  	return true;
>  }
>
> +static bool is_gpu_mapped(struct panthor_gem_object *bo,
> +			  enum panthor_gem_reclaim_state *state)
> +{
> +	struct drm_gpuvm *vm = NULL;
> +	struct drm_gpuvm_bo *vm_bo;
> +
> +	drm_gem_for_each_gpuvm_bo(vm_bo, &bo->base) {
> +		/* Skip evicted GPU mappings. */
> +		if (vm_bo->evicted)
> +			continue;
> +
> +		if (!vm) {
> +			*state = PANTHOR_GEM_GPU_MAPPED_PRIVATE;
> +			vm = vm_bo->vm;
> +		} else if (vm != vm_bo->vm) {

I might be wrong to think that no two VM_BO's for a given BO can have the same
VM, but if that were the case, then the above check could be omitted and left
as an 'else'.

> +			*state = PANTHOR_GEM_GPU_MAPPED_SHARED;
> +			break;
> +		}
> +	}
> +
> +	return !!vm;
> +}
> +
> +static enum panthor_gem_reclaim_state
> +panthor_gem_evaluate_reclaim_state_locked(struct panthor_gem_object *bo)
> +{
> +	enum panthor_gem_reclaim_state gpu_mapped_state;
> +
> +	dma_resv_assert_held(bo->base.resv);
> +	lockdep_assert_held(&bo->base.gpuva.lock);
> +
> +	/* If pages have not been allocated, there's nothing to reclaim. */
> +	if (!bo->backing.pages)
> +		return PANTHOR_GEM_UNRECLAIMABLE;
> +
> +	/* If memory is pinned, we prevent reclaim. */
> +	if (refcount_read(&bo->backing.pin_count))
> +		return PANTHOR_GEM_UNRECLAIMABLE;
> +
> +	if (is_gpu_mapped(bo, &gpu_mapped_state))
> +		return gpu_mapped_state;
> +
> +	if (refcount_read(&bo->cmap.mmap_count))
> +		return PANTHOR_GEM_MMAPPED;
> +
> +	return PANTHOR_GEM_UNUSED;
> +}
> +
> +void panthor_gem_update_reclaim_state_locked(struct panthor_gem_object *bo,
> +					     enum panthor_gem_reclaim_state *old_statep)
> +{
> +	struct panthor_device *ptdev = container_of(bo->base.dev, struct panthor_device, base);
> +	enum panthor_gem_reclaim_state old_state = bo->reclaim_state;
> +	enum panthor_gem_reclaim_state new_state;
> +	bool was_gpu_mapped, is_gpu_mapped;
> +
> +	if (old_statep)
> +		*old_statep = old_state;
> +
> +	new_state = panthor_gem_evaluate_reclaim_state_locked(bo);
> +	if (new_state == old_state)
> +		return;
> +
> +	was_gpu_mapped = old_state == PANTHOR_GEM_GPU_MAPPED_SHARED ||
> +			 old_state == PANTHOR_GEM_GPU_MAPPED_PRIVATE;
> +	is_gpu_mapped = new_state == PANTHOR_GEM_GPU_MAPPED_SHARED ||
> +			new_state == PANTHOR_GEM_GPU_MAPPED_PRIVATE;
> +
> +	if (is_gpu_mapped && !was_gpu_mapped)
> +		ptdev->reclaim.gpu_mapped_count += bo->base.size >> PAGE_SHIFT;
> +	else if (!is_gpu_mapped && was_gpu_mapped)
> +		ptdev->reclaim.gpu_mapped_count -= bo->base.size >> PAGE_SHIFT;
> +
> +	switch (new_state) {
> +	case PANTHOR_GEM_UNUSED:
> +		drm_gem_lru_move_tail(&ptdev->reclaim.unused, &bo->base);
> +		break;
> +	case PANTHOR_GEM_MMAPPED:
> +		drm_gem_lru_move_tail(&ptdev->reclaim.mmapped, &bo->base);
> +		break;
> +	case PANTHOR_GEM_GPU_MAPPED_PRIVATE:
> +		panthor_vm_update_bo_reclaim_lru_locked(bo);
> +		break;
> +	case PANTHOR_GEM_GPU_MAPPED_SHARED:
> +		drm_gem_lru_move_tail(&ptdev->reclaim.gpu_mapped_shared, &bo->base);
> +		break;
> +	case PANTHOR_GEM_UNRECLAIMABLE:
> +		drm_gem_lru_remove(&bo->base);
> +		break;
> +	default:
> +		drm_WARN(&ptdev->base, true, "invalid GEM reclaim state (%d)\n", new_state);
> +		break;
> +	}
> +
> +	bo->reclaim_state = new_state;
> +}
> +
>  static void
>  panthor_gem_backing_cleanup_locked(struct panthor_gem_object *bo)
>  {
> @@ -157,8 +258,12 @@ static int panthor_gem_backing_pin_locked(struct panthor_gem_object *bo)
>  		return 0;
>
>  	ret = panthor_gem_backing_get_pages_locked(bo);
> -	if (!ret)
> +	if (!ret) {
>  		refcount_set(&bo->backing.pin_count, 1);
> +		mutex_lock(&bo->base.gpuva.lock);
> +		panthor_gem_update_reclaim_state_locked(bo, NULL);
> +		mutex_unlock(&bo->base.gpuva.lock);
> +	}
>
>  	return ret;
>  }
> @@ -172,6 +277,9 @@ static void panthor_gem_backing_unpin_locked(struct panthor_gem_object *bo)
>  		/* We don't release anything when pin_count drops to zero.
>  		 * Pages stay there until an explicit cleanup is requested.
>  		 */
> +		mutex_lock(&bo->base.gpuva.lock);
> +		panthor_gem_update_reclaim_state_locked(bo, NULL);
> +		mutex_unlock(&bo->base.gpuva.lock);
>  	}
>  }
>
> @@ -535,6 +643,46 @@ void panthor_gem_unpin(struct panthor_gem_object *bo)
>  	dma_resv_unlock(bo->base.resv);
>  }
>
> +int panthor_gem_swapin_locked(struct panthor_gem_object *bo)
> +{
> +	struct sg_table *sgt;
> +	int ret;
> +
> +	dma_resv_assert_held(bo->base.resv);
> +
> +	if (drm_WARN_ON_ONCE(bo->base.dev, drm_gem_is_imported(&bo->base)))
> +		return -EINVAL;
> +

Following call is redundant because it's already being done in panthor_gem_dev_map_get_sgt_locked().

> +	ret = panthor_gem_backing_get_pages_locked(bo);
> +	if (ret)
> +		return ret;
> +
> +	sgt = panthor_gem_dev_map_get_sgt_locked(bo);
> +	if (IS_ERR(sgt))
> +		return PTR_ERR(sgt);
> +
> +	return 0;
> +}
> +
> +static void panthor_gem_evict_locked(struct panthor_gem_object *bo)
> +{
> +	dma_resv_assert_held(bo->base.resv);
> +	lockdep_assert_held(&bo->base.gpuva.lock);
> +
> +	if (drm_WARN_ON_ONCE(bo->base.dev, drm_gem_is_imported(&bo->base)))
> +		return;
> +
> +	if (drm_WARN_ON_ONCE(bo->base.dev, refcount_read(&bo->backing.pin_count)))
> +		return;
> +
> +	if (drm_WARN_ON_ONCE(bo->base.dev, !bo->backing.pages))
> +		return;
> +
> +	panthor_gem_dev_map_cleanup_locked(bo);
> +	panthor_gem_backing_cleanup_locked(bo);
> +	panthor_gem_update_reclaim_state_locked(bo, NULL);
> +}
> +
>  static struct sg_table *panthor_gem_get_sg_table(struct drm_gem_object *obj)
>  {
>  	struct panthor_gem_object *bo = to_panthor_bo(obj);
> @@ -607,8 +755,12 @@ static int panthor_gem_mmap(struct drm_gem_object *obj, struct vm_area_struct *v
>
>  	if (!refcount_inc_not_zero(&bo->cmap.mmap_count)) {
>  		dma_resv_lock(obj->resv, NULL);
> -		if (!refcount_inc_not_zero(&bo->cmap.mmap_count))
> +		if (!refcount_inc_not_zero(&bo->cmap.mmap_count)) {
>  			refcount_set(&bo->cmap.mmap_count, 1);
> +			mutex_lock(&bo->base.gpuva.lock);
> +			panthor_gem_update_reclaim_state_locked(bo, NULL);
> +			mutex_unlock(&bo->base.gpuva.lock);
> +		}
>  		dma_resv_unlock(obj->resv);
>  	}
>
> @@ -690,6 +842,10 @@ static vm_fault_t blocking_page_setup(struct vm_fault *vmf,
>  	} else {
>  		struct page *page = bo->backing.pages[page_offset];
>
> +		mutex_lock(&bo->base.gpuva.lock);
> +		panthor_gem_update_reclaim_state_locked(bo, NULL);
> +		mutex_unlock(&bo->base.gpuva.lock);
> +
>  		if (mmap_lock_held)
>  			ret = insert_page(vmf, page);
>  		else
> @@ -763,7 +919,9 @@ static void panthor_gem_vm_close(struct vm_area_struct *vma)
>
>  	dma_resv_lock(bo->base.resv, NULL);
>  	if (refcount_dec_and_test(&bo->cmap.mmap_count)) {
> -		/* Nothing to do, pages are reclaimed lazily. */
> +		mutex_lock(&bo->base.gpuva.lock);
> +		panthor_gem_update_reclaim_state_locked(bo, NULL);
> +		mutex_unlock(&bo->base.gpuva.lock);
>  	}
>  	dma_resv_unlock(bo->base.resv);
>
> @@ -800,6 +958,7 @@ panthor_gem_alloc_object(uint32_t flags)
>  	if (!bo)
>  		return ERR_PTR(-ENOMEM);
>
> +	bo->reclaim_state = PANTHOR_GEM_UNRECLAIMABLE;
>  	bo->base.funcs = &panthor_gem_funcs;
>  	bo->flags = flags;
>  	mutex_init(&bo->label.lock);
> @@ -958,6 +1117,7 @@ panthor_gem_sync(struct drm_gem_object *obj, u32 type,
>  	struct sg_table *sgt;
>  	struct scatterlist *sgl;
>  	unsigned int count;
> +	int ret;
>
>  	/* Make sure the range is in bounds. */
>  	if (offset + size < offset || offset + size > bo->base.size)
> @@ -984,9 +1144,21 @@ panthor_gem_sync(struct drm_gem_object *obj, u32 type,
>  	if (size == 0)
>  		return 0;
>
> -	sgt = panthor_gem_get_dev_sgt(bo);
> -	if (IS_ERR(sgt))
> -		return PTR_ERR(sgt);
> +	ret = dma_resv_lock_interruptible(bo->base.resv, NULL);
> +	if (ret)
> +		return ret;
> +
> +	/* If there's no pages, there's no point pulling those back, bail out early. */
> +	if (!bo->backing.pages) {
> +		ret = 0;
> +		goto out_unlock;
> +	}
> +
> +	sgt = panthor_gem_dev_map_get_sgt_locked(bo);
> +	if (IS_ERR(sgt)) {
> +		ret = PTR_ERR(sgt);
> +		goto out_unlock;
> +	}
>
>  	for_each_sgtable_dma_sg(sgt, sgl, count) {
>  		if (size == 0)
> @@ -1030,7 +1202,11 @@ panthor_gem_sync(struct drm_gem_object *obj, u32 type,
>  			dma_sync_single_for_cpu(dma_dev, paddr, len, DMA_FROM_DEVICE);
>  	}
>
> -	return 0;
> +	ret = 0;
> +
> +out_unlock:
> +	dma_resv_unlock(bo->base.resv);
> +	return ret;
>  }
>
>  /**
> @@ -1040,11 +1216,13 @@ panthor_gem_sync(struct drm_gem_object *obj, u32 type,
>   */
>  void panthor_kernel_bo_destroy(struct panthor_kernel_bo *bo)
>  {
> +	struct panthor_device *ptdev;
>  	struct panthor_vm *vm;
>
>  	if (IS_ERR_OR_NULL(bo))
>  		return;
>
> +	ptdev = container_of(bo->obj->dev, struct panthor_device, base);
>  	vm = bo->vm;
>  	panthor_kernel_bo_vunmap(bo);
>
> @@ -1052,6 +1230,8 @@ void panthor_kernel_bo_destroy(struct panthor_kernel_bo *bo)
>  		    to_panthor_bo(bo->obj)->exclusive_vm_root_gem != panthor_vm_root_gem(vm));
>  	panthor_vm_unmap_range(vm, bo->va_node.start, bo->va_node.size);
>  	panthor_vm_free_va(vm, &bo->va_node);
> +	if (vm == panthor_fw_vm(ptdev))
> +		panthor_gem_unpin(to_panthor_bo(bo->obj));
>  	drm_gem_object_put(bo->obj);
>  	panthor_vm_put(vm);
>  	kfree(bo);
> @@ -1100,6 +1280,12 @@ panthor_kernel_bo_create(struct panthor_device *ptdev, struct panthor_vm *vm,
>
>  	kbo->obj = &bo->base;
>
> +	if (vm == panthor_fw_vm(ptdev)) {
> +		ret = panthor_gem_pin(bo);
> +		if (ret)
> +			goto err_put_obj;
> +	}
> +
>  	panthor_gem_kernel_bo_set_label(kbo, name);
>
>  	/* The system and GPU MMU page size might differ, which becomes a
> @@ -1111,7 +1297,7 @@ panthor_kernel_bo_create(struct panthor_device *ptdev, struct panthor_vm *vm,
>  	size = ALIGN(size, panthor_vm_page_size(vm));
>  	ret = panthor_vm_alloc_va(vm, gpu_va, size, &kbo->va_node);
>  	if (ret)
> -		goto err_put_obj;
> +		goto err_unpin;
>
>  	ret = panthor_vm_map_bo_range(vm, bo, 0, size, kbo->va_node.start, vm_map_flags);
>  	if (ret)
> @@ -1123,6 +1309,10 @@ panthor_kernel_bo_create(struct panthor_device *ptdev, struct panthor_vm *vm,
>  err_free_va:
>  	panthor_vm_free_va(vm, &kbo->va_node);
>
> +err_unpin:
> +	if (vm == panthor_fw_vm(ptdev))
> +		panthor_gem_unpin(bo);
> +
>  err_put_obj:
>  	drm_gem_object_put(&bo->base);
>
> @@ -1131,6 +1321,233 @@ panthor_kernel_bo_create(struct panthor_device *ptdev, struct panthor_vm *vm,
>  	return ERR_PTR(ret);
>  }
>
> +static bool can_swap(void)
> +{
> +	return get_nr_swap_pages() > 0;
> +}
> +
> +static bool can_block(struct shrink_control *sc)
> +{
> +	if (!(sc->gfp_mask & __GFP_DIRECT_RECLAIM))
> +		return false;
> +	return current_is_kswapd() || (sc->gfp_mask & __GFP_RECLAIM);
> +}
> +
> +static unsigned long
> +panthor_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc)
> +{
> +	struct panthor_device *ptdev = shrinker->private_data;
> +	unsigned long count;
> +
> +	/* We currently don't have a flag to tell when the content of a
> +	 * BO can be discarded.
> +	 */
> +	if (!can_swap())
> +		return 0;
> +
> +	count = ptdev->reclaim.unused.count;
> +	count += ptdev->reclaim.mmapped.count;
> +
> +	if (can_block(sc))
> +		count += ptdev->reclaim.gpu_mapped_count;
> +
> +	return count ? count : SHRINK_EMPTY;
> +}
> +
> +static bool panthor_gem_try_evict_no_resv_wait(struct drm_gem_object *obj,
> +					       struct ww_acquire_ctx *ticket)
> +{
> +	/*
> +	 * Track last locked entry for unwinding locks in error and
> +	 * success paths
> +	 */
> +	struct panthor_gem_object *bo = to_panthor_bo(obj);
> +	struct drm_gpuvm_bo *vm_bo, *last_locked = NULL;
> +	enum panthor_gem_reclaim_state old_state;
> +	int ret = 0;
> +
> +	/* To avoid potential lock ordering issue between bo_gpuva and
> +	 * mapping->i_mmap_rwsem, unmap the pages from CPU side before
> +	 * acquring the bo_gpuva lock. As the bo_resv lock is held, CPU
> +	 * page fault handler won't be able to map in the pages whilst
> +	 * eviction is in progress.
> +	 */
> +	drm_vma_node_unmap(&bo->base.vma_node, bo->base.dev->anon_inode->i_mapping);
> +
> +	/* We take this lock when walking the list to prevent
> +	 * insertion/deletion.
> +	 */
> +	/* We can only trylock in that path, because
> +	 * - allocation might happen while some of these locks are held
> +	 * - lock ordering is different in other paths
> +	 *     vm_resv -> bo_resv -> bo_gpuva
> +	 *     vs
> +	 *     bo_resv -> bo_gpuva -> vm_resv
> +	 *
> +	 * If we fail to lock that's fine, we back off and will get
> +	 * back to it later.
> +	 */
> +	if (!mutex_trylock(&bo->base.gpuva.lock))
> +		return false;
> +
> +	drm_gem_for_each_gpuvm_bo(vm_bo, obj) {
> +		struct dma_resv *resv = drm_gpuvm_resv(vm_bo->vm);
> +
> +		if (resv == obj->resv)
> +			continue;
> +
> +		if (!dma_resv_trylock(resv)) {
> +			ret = -EDEADLK;
> +			goto out_unlock;
> +		}
> +
> +		last_locked = vm_bo;
> +	}
> +
> +	/* Update the state before trying to evict the buffer, if the state was
> +	 * updated to something that's harder to reclaim (higher value in the
> +	 * enum), skip it (will be processed when the relevant LRU is).
> +	 */
> +	panthor_gem_update_reclaim_state_locked(bo, &old_state);
> +	if (old_state < bo->reclaim_state) {
> +		ret = -EAGAIN;
> +		goto out_unlock;
> +	}
> +
> +	/* Couldn't teardown the GPU mappings? Skip. */
> +	ret = panthor_vm_evict_bo_mappings_locked(bo);
> +	if (ret)
> +		goto out_unlock;
> +
> +	/* If everything went fine, evict the object. */
> +	panthor_gem_evict_locked(bo);
> +
> +out_unlock:
> +	if (last_locked) {
> +		drm_gem_for_each_gpuvm_bo(vm_bo, obj) {
> +			struct dma_resv *resv = drm_gpuvm_resv(vm_bo->vm);
> +
> +			if (resv == obj->resv)
> +				continue;
> +
> +			dma_resv_unlock(resv);
> +
> +			if (last_locked == vm_bo)
> +				break;
> +		}
> +	}
> +	mutex_unlock(&bo->base.gpuva.lock);
> +
> +	return ret == 0;
> +}
> +
> +static bool panthor_gem_try_evict(struct drm_gem_object *obj,
> +				  struct ww_acquire_ctx *ticket)
> +{
> +	struct panthor_gem_object *bo = to_panthor_bo(obj);
> +
> +	/* Wait was too long, skip. */
> +	if (dma_resv_wait_timeout(obj->resv, DMA_RESV_USAGE_BOOKKEEP, false, 10) <= 0)
> +		return false;
> +
> +	return panthor_gem_try_evict_no_resv_wait(&bo->base, ticket);
> +}
> +
> +static unsigned long
> +panthor_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
> +{
> +	struct panthor_device *ptdev = shrinker->private_data;
> +	unsigned long remaining = 0;
> +	unsigned long freed = 0;
> +
> +	if (!can_swap())
> +		goto out;
> +
> +	freed += drm_gem_lru_scan(&ptdev->reclaim.unused,
> +				  sc->nr_to_scan - freed, &remaining,
> +				  panthor_gem_try_evict_no_resv_wait, NULL);
> +	if (freed >= sc->nr_to_scan)
> +		goto out;
> +
> +	freed += drm_gem_lru_scan(&ptdev->reclaim.mmapped,
> +				  sc->nr_to_scan - freed, &remaining,
> +				  panthor_gem_try_evict_no_resv_wait, NULL);
> +	if (freed >= sc->nr_to_scan)
> +		goto out;
> +
> +	if (!can_block(sc))
> +		goto out;
> +
> +	freed += panthor_mmu_reclaim_priv_bos(ptdev, sc->nr_to_scan - freed,
> +					      &remaining, panthor_gem_try_evict);
> +	if (freed >= sc->nr_to_scan)
> +		goto out;
> +
> +	freed += drm_gem_lru_scan(&ptdev->reclaim.gpu_mapped_shared,
> +				  sc->nr_to_scan - freed, &remaining,
> +				  panthor_gem_try_evict, NULL);
> +
> +out:
> +#ifdef CONFIG_DEBUG_FS
> +	/* This is racy, but that's okay, because this is just debugfs
> +	 * reporting and doesn't need to be accurate.
> +	 */
> +	ptdev->reclaim.nr_pages_reclaimed_on_last_scan = freed;
> +#endif
> +
> +	/* If there are things to reclaim, try a couple times before giving up. */
> +	if (!freed && remaining > 0 &&
> +	    atomic_inc_return(&ptdev->reclaim.retry_count) < 2)
> +		return 0;
> +
> +	atomic_set(&ptdev->reclaim.retry_count, 0);
> +
> +	if (freed)
> +		return freed;
> +
> +	/* There's nothing left to reclaim, or the resources are contended. Give up now. */
> +	return SHRINK_STOP;
> +}
> +
> +int panthor_gem_shrinker_init(struct panthor_device *ptdev)
> +{
> +	struct shrinker *shrinker;
> +	int ret;
> +
> +	ret = drmm_mutex_init(&ptdev->base, &ptdev->reclaim.lock);
> +	if (ret)
> +		return ret;
> +
> +	INIT_LIST_HEAD(&ptdev->reclaim.vms);
> +	drm_gem_lru_init(&ptdev->reclaim.unused, &ptdev->reclaim.lock);
> +	drm_gem_lru_init(&ptdev->reclaim.mmapped, &ptdev->reclaim.lock);
> +	drm_gem_lru_init(&ptdev->reclaim.gpu_mapped_shared, &ptdev->reclaim.lock);
> +	ptdev->reclaim.gpu_mapped_count = 0;
> +
> +	/* Teach lockdep about lock ordering wrt. shrinker: */
> +	fs_reclaim_acquire(GFP_KERNEL);
> +	might_lock(&ptdev->reclaim.lock);
> +	fs_reclaim_release(GFP_KERNEL);
> +
> +	shrinker = shrinker_alloc(0, "drm-panthor-gem");
> +	if (!shrinker)
> +		return -ENOMEM;
> +
> +	shrinker->count_objects = panthor_gem_shrinker_count;
> +	shrinker->scan_objects = panthor_gem_shrinker_scan;
> +	shrinker->private_data = ptdev;
> +	ptdev->reclaim.shrinker = shrinker;
> +
> +	shrinker_register(shrinker);
> +	return 0;
> +}
> +
> +void panthor_gem_shrinker_unplug(struct panthor_device *ptdev)
> +{
> +	if (ptdev->reclaim.shrinker)
> +		shrinker_free(ptdev->reclaim.shrinker);
> +}
> +
>  #ifdef CONFIG_DEBUG_FS
>  struct gem_size_totals {
>  	size_t size;
> @@ -1174,6 +1591,7 @@ static void panthor_gem_debugfs_bo_print(struct panthor_gem_object *bo,
>  					 struct seq_file *m,
>  					 struct gem_size_totals *totals)
>  {
> +	enum panthor_gem_reclaim_state reclaim_state = bo->reclaim_state;
>  	unsigned int refcount = kref_read(&bo->base.refcount);
>  	char creator_info[32] = {};
>  	size_t resident_size;
> @@ -1209,6 +1627,8 @@ static void panthor_gem_debugfs_bo_print(struct panthor_gem_object *bo,
>
>  	totals->size += bo->base.size;
>  	totals->resident += resident_size;
> +	if (reclaim_state != PANTHOR_GEM_UNRECLAIMABLE)
> +		totals->reclaimable += resident_size;
>  }
>
>  static void panthor_gem_debugfs_print_bos(struct panthor_device *ptdev,
> @@ -1249,10 +1669,42 @@ static struct drm_info_list panthor_gem_debugfs_list[] = {
>  	{ "gems", panthor_gem_show_bos, 0, NULL },
>  };
>
> +static int shrink_get(void *data, u64 *val)
> +{
> +	struct panthor_device *ptdev =
> +		container_of(data, struct panthor_device, base);
> +
> +	*val = ptdev->reclaim.nr_pages_reclaimed_on_last_scan;
> +	return 0;
> +}
> +
> +static int shrink_set(void *data, u64 val)
> +{
> +	struct panthor_device *ptdev =
> +		container_of(data, struct panthor_device, base);
> +	struct shrink_control sc = {
> +		.gfp_mask = GFP_KERNEL,
> +		.nr_to_scan = val,
> +	};
> +
> +	fs_reclaim_acquire(GFP_KERNEL);
> +	if (ptdev->reclaim.shrinker)
> +		panthor_gem_shrinker_scan(ptdev->reclaim.shrinker, &sc);
> +	fs_reclaim_release(GFP_KERNEL);
> +
> +	return 0;
> +}
> +
> +DEFINE_DEBUGFS_ATTRIBUTE(panthor_gem_debugfs_shrink_fops,
> +			 shrink_get, shrink_set,
> +			 "0x%08llx\n");
> +
>  void panthor_gem_debugfs_init(struct drm_minor *minor)
>  {
>  	drm_debugfs_create_files(panthor_gem_debugfs_list,
>  				 ARRAY_SIZE(panthor_gem_debugfs_list),
>  				 minor->debugfs_root, minor);
> +	debugfs_create_file("shrink", 0600, minor->debugfs_root,
> +			    minor->dev, &panthor_gem_debugfs_shrink_fops);
>  }
>  #endif
> diff --git a/drivers/gpu/drm/panthor/panthor_gem.h b/drivers/gpu/drm/panthor/panthor_gem.h
> index c0a18dca732c..30281fad7327 100644
> --- a/drivers/gpu/drm/panthor/panthor_gem.h
> +++ b/drivers/gpu/drm/panthor/panthor_gem.h
> @@ -1,6 +1,7 @@
>  /* SPDX-License-Identifier: GPL-2.0 or MIT */
>  /* Copyright 2019 Linaro, Ltd, Rob Herring <robh@kernel.org> */
>  /* Copyright 2023 Collabora ltd. */
> +/* Copyright 2025 ARM Limited. All rights reserved. */
>
>  #ifndef __PANTHOR_GEM_H__
>  #define __PANTHOR_GEM_H__
> @@ -93,6 +94,65 @@ struct panthor_gem_dev_map {
>  	struct sg_table *sgt;
>  };
>
> +/**
> + * enum panthor_gem_reclaim_state - Reclaim state of a GEM object
> + *
> + * This is defined in descending reclaimability order and some part
> + * of the code depends on that.
> + */
> +enum panthor_gem_reclaim_state {
> +	/**
> +	 * @PANTHOR_GEM_UNUSED: GEM is currently unused
> +	 *
> +	 * This can happen when the GEM was previously vmap-ed, mmap-ed,
> +	 * and/or GPU mapped and got unmapped. Because pages are lazily
> +	 * returned to the shmem layer, we want to keep a list of such
> +	 * BOs, because they should be fairly easy to reclaim (no need
> +	 * to wait for GPU to be done, and no need to tear down user
> +	 * mappings either).
> +	 */
> +	PANTHOR_GEM_UNUSED,
> +
> +	/**
> +	 * @PANTHOR_GEM_MMAPPED: GEM is currently mmap-ed
> +	 *
> +	 * When a GEM has pages allocated and the mmap_count is > 0, the
> +	 * GEM is placed in the mmapped list. This comes right after
> +	 * unused because we can relatively easily tear down user mappings.
> +	 */
> +	PANTHOR_GEM_MMAPPED,
> +
> +	/**
> +	 * @PANTHOR_GEM_GPU_MAPPED_PRIVATE: GEM is GPU mapped to only one VM
> +	 *
> +	 * When a GEM is mapped to a single VM, reclaim requests have more
> +	 * chances to succeed, because we only need to synchronize against
> +	 * a single GPU context. This is more annoying than reclaiming
> +	 * mmap-ed pages still, because we have to wait for in-flight jobs
> +	 * to land, and we might not be able to acquire all necessary locks
> +	 * at reclaim time either.
> +	 */
> +	PANTHOR_GEM_GPU_MAPPED_PRIVATE,
> +
> +	/**
> +	 * @PANTHOR_GEM_GPU_MAPPED_SHARED: GEM is GPU mapped to multiple VMs
> +	 *
> +	 * Like PANTHOR_GEM_GPU_MAPPED_PRIVATE, but the synchronization across
> +	 * VMs makes such BOs harder to reclaim.
> +	 */
> +	PANTHOR_GEM_GPU_MAPPED_SHARED,
> +
> +	/**
> +	 * @PANTHOR_GEM_UNRECLAIMABLE: GEM can't be reclaimed
> +	 *
> +	 * Happens when the GEM memory is pinned. It's also the state all GEM
> +	 * objects start in, because no memory is allocated until explicitly
> +	 * requested by a CPU or GPU map, meaning there's nothing to reclaim
> +	 * until such an allocation happens.
> +	 */
> +	PANTHOR_GEM_UNRECLAIMABLE,
> +};
> +
>  /**
>   * struct panthor_gem_object - Driver specific GEM object.
>   */
> @@ -109,6 +169,9 @@ struct panthor_gem_object {
>  	/** @dmap: Device mapping state */
>  	struct panthor_gem_dev_map dmap;
>
> +	/** @reclaim_state: Cached reclaim state */
> +	enum panthor_gem_reclaim_state reclaim_state;
> +
>  	/**
>  	 * @exclusive_vm_root_gem: Root GEM of the exclusive VM this GEM object
>  	 * is attached to.
> @@ -190,6 +253,11 @@ struct sg_table *
>  panthor_gem_get_dev_sgt(struct panthor_gem_object *bo);
>  int panthor_gem_pin(struct panthor_gem_object *bo);
>  void panthor_gem_unpin(struct panthor_gem_object *bo);
> +int panthor_gem_swapin_locked(struct panthor_gem_object *bo);
> +void panthor_gem_update_reclaim_state_locked(struct panthor_gem_object *bo,
> +					     enum panthor_gem_reclaim_state *old_state);
> +int panthor_gem_shrinker_init(struct panthor_device *ptdev);
> +void panthor_gem_shrinker_unplug(struct panthor_device *ptdev);
>
>  void panthor_gem_bo_set_label(struct drm_gem_object *obj, const char *label);
>  void panthor_gem_kernel_bo_set_label(struct panthor_kernel_bo *bo, const char *label);
> diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
> index 5d07c1b96e0a..4b415aaedaa9 100644
> --- a/drivers/gpu/drm/panthor/panthor_mmu.c
> +++ b/drivers/gpu/drm/panthor/panthor_mmu.c
> @@ -1,6 +1,7 @@
>  // SPDX-License-Identifier: GPL-2.0 or MIT
>  /* Copyright 2019 Linaro, Ltd, Rob Herring <robh@kernel.org> */
>  /* Copyright 2023 Collabora ltd. */
> +/* Copyright 2025 ARM Limited. All rights reserved. */
>
>  #include <drm/drm_debugfs.h>
>  #include <drm/drm_drv.h>
> @@ -131,6 +132,9 @@ struct panthor_vma {
>  	 * Only map related flags are accepted.
>  	 */
>  	u32 flags;
> +
> +	/** @evicted: True if the VMA has been evicted. */
> +	bool evicted;
>  };
>
>  /**
> @@ -191,13 +195,8 @@ struct panthor_vm_op_ctx {
>  		/** @map.bo_offset: Offset in the buffer object. */
>  		u64 bo_offset;
>
> -		/**
> -		 * @map.sgt: sg-table pointing to pages backing the GEM object.
> -		 *
> -		 * This is gathered at job creation time, such that we don't have
> -		 * to allocate in ::run_job().
> -		 */
> -		struct sg_table *sgt;
> +		/** @map.bo: the BO being mapped. */
> +		struct panthor_gem_object *bo;
>
>  		/**
>  		 * @map.new_vma: The new VMA object that will be inserted to the VA tree.
> @@ -385,6 +384,18 @@ struct panthor_vm {
>  		/** @locked_region.size: Size of the locked region. */
>  		u64 size;
>  	} locked_region;
> +
> +	/** @reclaim: Fields related to BO reclaim. */
> +	struct {
> +		/** @reclaim.lru: LRU of BOs that are only mapped to this VM. */
> +		struct drm_gem_lru lru;
> +
> +		/**
> +		 * @reclaim.lru_node: Node used to insert the VM in
> +		 * panthor_device::reclaim::vms.
> +		 */
> +		struct list_head lru_node;
> +	} reclaim;
>  };
>
>  /**
> @@ -689,6 +700,16 @@ int panthor_vm_active(struct panthor_vm *vm)
>  	if (refcount_inc_not_zero(&vm->as.active_cnt))
>  		goto out_dev_exit;
>
> +	/* As soon as active is called, we place the VM at the end of the VM LRU.
> +	 * If something fails after that, the only downside is that this VM that
> +	 * never became active in the first place will be reclaimed last, but
> +	 * that's an acceptable trade-off.
> +	 */
> +	mutex_lock(&ptdev->reclaim.lock);
> +	if (vm->reclaim.lru.count)
> +		list_move_tail(&vm->reclaim.lru_node, &ptdev->reclaim.vms);
> +	mutex_unlock(&ptdev->reclaim.lock);
> +
>  	/* Make sure we don't race with lock/unlock_region() calls
>  	 * happening around VM bind operations.
>  	 */
> @@ -1084,7 +1105,15 @@ static void panthor_vm_bo_free(struct drm_gpuvm_bo *vm_bo)
>  {
>  	struct panthor_gem_object *bo = to_panthor_bo(vm_bo->obj);
>
> -	panthor_gem_unpin(bo);
> +	/* We couldn't call this when we unlinked, because the resv lock can't
> +	 * be taken in the dma signalling path, so call it now.
> +	 */
> +	dma_resv_lock(bo->base.resv, NULL);
> +	mutex_lock(&bo->base.gpuva.lock);
> +	panthor_gem_update_reclaim_state_locked(bo, NULL);
> +	mutex_unlock(&bo->base.gpuva.lock);
> +	dma_resv_unlock(bo->base.resv);
> +
>  	kfree(vm_bo);
>  }
>
> @@ -1105,6 +1134,11 @@ static void panthor_vm_cleanup_op_ctx(struct panthor_vm_op_ctx *op_ctx,
>  	if (op_ctx->map.vm_bo)
>  		drm_gpuvm_bo_put_deferred(op_ctx->map.vm_bo);
>
> +	if (op_ctx->map.bo) {
> +		panthor_gem_unpin(op_ctx->map.bo);
> +		drm_gem_object_put(&op_ctx->map.bo->base);
> +	}
> +
>  	for (u32 i = 0; i < ARRAY_SIZE(op_ctx->preallocated_vmas); i++)
>  		kfree(op_ctx->preallocated_vmas[i]);
>
> @@ -1264,18 +1298,17 @@ static int panthor_vm_prepare_map_op_ctx(struct panthor_vm_op_ctx *op_ctx,
>  	if (ret)
>  		goto err_cleanup;
>
> +	drm_gem_object_get(&bo->base);
> +	op_ctx->map.bo = bo;
> +
>  	sgt = panthor_gem_get_dev_sgt(bo);
>  	if (IS_ERR(sgt)) {
> -		panthor_gem_unpin(bo);
>  		ret = PTR_ERR(sgt);
>  		goto err_cleanup;
>  	}
>
> -	op_ctx->map.sgt = sgt;
> -
>  	preallocated_vm_bo = drm_gpuvm_bo_create(&vm->base, &bo->base);
>  	if (!preallocated_vm_bo) {
> -		panthor_gem_unpin(bo);
>  		ret = -ENOMEM;
>  		goto err_cleanup;
>  	}
> @@ -1294,6 +1327,13 @@ static int panthor_vm_prepare_map_op_ctx(struct panthor_vm_op_ctx *op_ctx,
>  		dma_resv_unlock(panthor_vm_resv(vm));
>  	}
>
> +	/* And finally update the BO state. */
> +	dma_resv_lock(bo->base.resv, NULL);
> +	mutex_lock(&bo->base.gpuva.lock);
> +	panthor_gem_update_reclaim_state_locked(bo, NULL);
> +	mutex_unlock(&bo->base.gpuva.lock);
> +	dma_resv_unlock(bo->base.resv);
> +
>  	return 0;
>
>  err_cleanup:
> @@ -1881,6 +1921,10 @@ static void panthor_vm_free(struct drm_gpuvm *gpuvm)
>  	struct panthor_vm *vm = container_of(gpuvm, struct panthor_vm, base);
>  	struct panthor_device *ptdev = vm->ptdev;
>
> +	mutex_lock(&ptdev->reclaim.lock);
> +	list_del_init(&vm->reclaim.lru_node);
> +	mutex_unlock(&ptdev->reclaim.lock);
> +
>  	mutex_lock(&vm->heaps.lock);
>  	if (drm_WARN_ON(&ptdev->base, vm->heaps.pool))
>  		panthor_heap_pool_destroy(vm->heaps.pool);
> @@ -2094,7 +2138,7 @@ static int panthor_gpuva_sm_step_map(struct drm_gpuva_op *op, void *priv)
>  	panthor_vma_init(vma, op_ctx->flags & PANTHOR_VM_MAP_FLAGS);
>
>  	ret = panthor_vm_map_pages(vm, op->map.va.addr, flags_to_prot(vma->flags),
> -				   op_ctx->map.sgt, op->map.gem.offset,
> +				   op_ctx->map.bo->dmap.sgt, op->map.gem.offset,
>  				   op->map.va.range);
>  	if (ret) {
>  		panthor_vm_op_ctx_return_vma(op_ctx, vma);
> @@ -2178,8 +2222,10 @@ static int panthor_gpuva_sm_step_remap(struct drm_gpuva_op *op,
>  	 * atomicity. panthor_vm_lock_region() bails out early if the new region
>  	 * is already part of the locked region, so no need to do this check here.
>  	 */
> -	panthor_vm_lock_region(vm, unmap_start, unmap_range);
> -	panthor_vm_unmap_pages(vm, unmap_start, unmap_range);
> +	if (!unmap_vma->evicted) {
> +		panthor_vm_lock_region(vm, unmap_start, unmap_range);
> +		panthor_vm_unmap_pages(vm, unmap_start, unmap_range);
> +	}
>
>  	if (op->remap.prev) {
>  		struct panthor_gem_object *bo = to_panthor_bo(op->remap.prev->gem.obj);
> @@ -2193,6 +2239,7 @@ static int panthor_gpuva_sm_step_remap(struct drm_gpuva_op *op,
>
>  		prev_vma = panthor_vm_op_ctx_get_vma(op_ctx);
>  		panthor_vma_init(prev_vma, unmap_vma->flags);
> +		prev_vma->evicted = unmap_vma->evicted;
>  	}
>
>  	if (op->remap.next) {
> @@ -2207,6 +2254,7 @@ static int panthor_gpuva_sm_step_remap(struct drm_gpuva_op *op,
>
>  		next_vma = panthor_vm_op_ctx_get_vma(op_ctx);
>  		panthor_vma_init(next_vma, unmap_vma->flags);
> +		next_vma->evicted = unmap_vma->evicted;
>  	}
>
>  	drm_gpuva_remap(prev_vma ? &prev_vma->base : NULL,
> @@ -2236,19 +2284,221 @@ static int panthor_gpuva_sm_step_unmap(struct drm_gpuva_op *op,
>  	struct panthor_vma *unmap_vma = container_of(op->unmap.va, struct panthor_vma, base);
>  	struct panthor_vm *vm = priv;
>
> -	panthor_vm_unmap_pages(vm, unmap_vma->base.va.addr,
> -			       unmap_vma->base.va.range);
> +	if (!unmap_vma->evicted) {
> +		panthor_vm_unmap_pages(vm, unmap_vma->base.va.addr,
> +				       unmap_vma->base.va.range);
> +	}
> +
>  	drm_gpuva_unmap(&op->unmap);
>  	panthor_vma_unlink(unmap_vma);
>  	return 0;
>  }
>
> +void panthor_vm_update_bo_reclaim_lru_locked(struct panthor_gem_object *bo)
> +{
> +	struct panthor_device *ptdev = container_of(bo->base.dev, struct panthor_device, base);
> +	struct panthor_vm *vm = NULL;
> +	struct drm_gpuvm_bo *vm_bo;
> +
> +	dma_resv_assert_held(bo->base.resv);
> +	lockdep_assert_held(&bo->base.gpuva.lock);
> +
> +	drm_gem_for_each_gpuvm_bo(vm_bo, &bo->base) {
> +		if (vm_bo->evicted)
> +			continue;
> +
> +		/* We're only supposed to have one non-evicted vm_bo in the list if we get
> +		 * there.
> +		 */
> +		drm_WARN_ON(&ptdev->base, vm);
> +		vm = container_of(vm_bo->vm, struct panthor_vm, base);
> +
> +		mutex_lock(&ptdev->reclaim.lock);
> +		drm_gem_lru_move_tail_locked(&vm->reclaim.lru, &bo->base);
> +		if (list_empty(&vm->reclaim.lru_node))
> +			list_move(&vm->reclaim.lru_node, &ptdev->reclaim.vms);
> +		mutex_unlock(&ptdev->reclaim.lock);
> +	}
> +}
> +
> +int panthor_vm_evict_bo_mappings_locked(struct panthor_gem_object *bo)
> +{
> +	struct drm_gpuvm_bo *vm_bo;
> +	int ret = 0;
> +
> +	drm_gem_for_each_gpuvm_bo(vm_bo, &bo->base) {
> +		struct panthor_vm *vm = container_of(vm_bo->vm, struct panthor_vm, base);
> +		struct drm_gpuva *va;
> +
> +		/* Skip already evicted GPU mappings. */
> +		if (vm_bo->evicted)
> +			continue;
> +
> +		if (!mutex_trylock(&vm->op_lock))
> +			return -EDEADLK;
> +
> +		drm_gpuvm_bo_evict(vm_bo, true);
> +		drm_gpuvm_bo_for_each_va(va, vm_bo) {
> +			struct panthor_vma *vma = container_of(va, struct panthor_vma, base);
> +
> +			if (vma->evicted)
> +				continue;
> +
> +			ret = panthor_vm_lock_region(vm, va->va.addr, va->va.range);
> +			if (ret)
> +				break;
> +
> +			panthor_vm_unmap_pages(vm, va->va.addr, va->va.range);
> +			panthor_vm_unlock_region(vm);
> +			vma->evicted = true;
> +		}
> +
> +		mutex_unlock(&vm->op_lock);
> +
> +		if (ret)
> +			break;
> +	}
> +
> +	return ret;
> +}
> +
> +static struct panthor_vma *select_evicted_vma(struct drm_gpuvm_bo *vm_bo,
> +					      struct panthor_vm_op_ctx *op_ctx)
> +{
> +	struct panthor_vm *vm = container_of(vm_bo->vm, struct panthor_vm, base);
> +	struct panthor_vma *first_evicted_vma = NULL;
> +	struct drm_gpuva *va;
> +
> +	/* Take op_lock to protect against va insertion/removal. */
> +	mutex_lock(&vm->op_lock);
> +	drm_gpuvm_bo_for_each_va(va, vm_bo) {
> +		struct panthor_vma *vma = container_of(va, struct panthor_vma, base);
> +
> +		if (vma->evicted) {
> +			first_evicted_vma = vma;
> +			panthor_vm_init_op_ctx(op_ctx, va->va.range, va->va.addr, vma->flags);
> +			op_ctx->map.bo_offset = va->gem.offset;
> +			break;
> +		}
> +	}
> +	mutex_unlock(&vm->op_lock);
> +
> +	return first_evicted_vma;
> +}
> +
> +static int remap_evicted_vma(struct drm_gpuvm_bo *vm_bo,
> +			     struct panthor_vma *evicted_vma,
> +			     struct panthor_vm_op_ctx *op_ctx)
> +{
> +	struct panthor_vm *vm = container_of(vm_bo->vm, struct panthor_vm, base);
> +	struct panthor_gem_object *bo = to_panthor_bo(vm_bo->obj);
> +	struct drm_gpuva *va;
> +	bool found = false;
> +	int ret;
> +
> +	ret = panthor_vm_op_ctx_prealloc_pts(op_ctx);
> +	if (ret)
> +		goto out_cleanup;
> +
> +	/* Take op_lock to protect against va insertion/removal. Note that the
> +	 * evicted_vma selection was done with the same lock held, but we had
> +	 * to release it so we can allocate PTs, because this very same lock
> +	 * is taken in a DMA-signalling path.
> +	 */
> +	mutex_lock(&vm->op_lock);
> +	drm_gpuvm_bo_for_each_va(va, vm_bo) {
> +		struct panthor_vma *vma = container_of(va, struct panthor_vma, base);
> +
> +		if (vma != evicted_vma)
> +			continue;
> +
> +		/* Because we had to release the lock between the evicted_vma selection
> +		 * and its repopulation, we can't rely solely on pointer equality (the
> +		 * VMA might have been freed and a new one allocated at the same address).
> +		 * If the evicted bit is still set, we're sure it's our VMA, because
> +		 * population/eviction is serialized with the BO resv lock.
> +		 */
> +		if (vma->evicted)
> +			found = true;
> +
> +		break;
> +	}
> +
> +	if (found) {
> +		vm->op_ctx = op_ctx;
> +		ret = panthor_vm_lock_region(vm, evicted_vma->base.va.addr,
> +					     evicted_vma->base.va.range);
> +		if (!ret) {
> +			ret = panthor_vm_map_pages(vm, evicted_vma->base.va.addr,
> +						   flags_to_prot(evicted_vma->flags),
> +						   bo->dmap.sgt,
> +						   evicted_vma->base.gem.offset,
> +						   evicted_vma->base.va.range);
> +		}
> +
> +		if (!ret)
> +			evicted_vma->evicted = false;
> +
> +		panthor_vm_unlock_region(vm);
> +		vm->op_ctx = NULL;
> +	}
> +
> +	mutex_unlock(&vm->op_lock);
> +
> +out_cleanup:
> +	panthor_vm_cleanup_op_ctx(op_ctx, vm);
> +	return ret;
> +}
> +
> +static int panthor_vm_restore_vmas(struct drm_gpuvm_bo *vm_bo)
> +{
> +	struct panthor_vm *vm = container_of(vm_bo->vm, struct panthor_vm, base);
> +	struct panthor_gem_object *bo = to_panthor_bo(vm_bo->obj);
> +	struct panthor_vm_op_ctx op_ctx;
> +
> +	if (drm_WARN_ON_ONCE(&vm->ptdev->base, !bo->dmap.sgt))
> +		return -EINVAL;
> +
> +	for (struct panthor_vma *vma = select_evicted_vma(vm_bo, &op_ctx);
> +	     vma; vma = select_evicted_vma(vm_bo, &op_ctx)) {
> +		int ret;
> +
> +		ret = remap_evicted_vma(vm_bo, vma, &op_ctx);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int panthor_vm_bo_validate(struct drm_gpuvm_bo *vm_bo,
> +				  struct drm_exec *exec)
> +{
> +	struct panthor_gem_object *bo = to_panthor_bo(vm_bo->obj);
> +	int ret;
> +
> +	ret = panthor_gem_swapin_locked(bo);
> +	if (ret)
> +		return ret;
> +
> +	ret = panthor_vm_restore_vmas(vm_bo);
> +	if (ret)
> +		return ret;
> +
> +	drm_gpuvm_bo_evict(vm_bo, false);
> +	mutex_lock(&bo->base.gpuva.lock);
> +	panthor_gem_update_reclaim_state_locked(bo, NULL);
> +	mutex_unlock(&bo->base.gpuva.lock);
> +	return 0;
> +}
> +
>  static const struct drm_gpuvm_ops panthor_gpuvm_ops = {
>  	.vm_free = panthor_vm_free,
>  	.vm_bo_free = panthor_vm_bo_free,
>  	.sm_step_map = panthor_gpuva_sm_step_map,
>  	.sm_step_remap = panthor_gpuva_sm_step_remap,
>  	.sm_step_unmap = panthor_gpuva_sm_step_unmap,
> +	.vm_bo_validate = panthor_vm_bo_validate,
>  };
>
>  /**
> @@ -2463,6 +2713,8 @@ panthor_vm_create(struct panthor_device *ptdev, bool for_mcu,
>  	vm->kernel_auto_va.start = auto_kernel_va_start;
>  	vm->kernel_auto_va.end = vm->kernel_auto_va.start + auto_kernel_va_size - 1;
>
> +	drm_gem_lru_init(&vm->reclaim.lru, &ptdev->reclaim.lock);
> +	INIT_LIST_HEAD(&vm->reclaim.lru_node);
>  	INIT_LIST_HEAD(&vm->node);
>  	INIT_LIST_HEAD(&vm->as.lru_node);
>  	vm->as.id = -1;
> @@ -2810,7 +3062,78 @@ int panthor_vm_prepare_mapped_bos_resvs(struct drm_exec *exec, struct panthor_vm
>  	if (ret)
>  		return ret;
>
> -	return drm_gpuvm_prepare_objects(&vm->base, exec, slot_count);
> +	ret = drm_gpuvm_prepare_objects(&vm->base, exec, slot_count);
> +	if (ret)
> +		return ret;
> +
> +	return drm_gpuvm_validate(&vm->base, exec);
> +}
> +
> +unsigned long
> +panthor_mmu_reclaim_priv_bos(struct panthor_device *ptdev,
> +			     unsigned int nr_to_scan, unsigned long *remaining,
> +			     bool (*shrink)(struct drm_gem_object *,
> +					    struct ww_acquire_ctx *))
> +{
> +	unsigned long freed = 0;
> +	LIST_HEAD(remaining_vms);
> +	LIST_HEAD(vms);
> +
> +	mutex_lock(&ptdev->reclaim.lock);
> +	list_splice_init(&ptdev->reclaim.vms, &vms);
> +
> +	while (freed < nr_to_scan) {
> +		struct panthor_vm *vm;
> +
> +		vm = list_first_entry_or_null(&vms, typeof(*vm),
> +					      reclaim.lru_node);
> +		if (!vm)
> +			break;
> +
> +		if (!kref_get_unless_zero(&vm->base.kref)) {
> +			list_del_init(&vm->reclaim.lru_node);
> +			continue;
> +		}
> +
> +		mutex_unlock(&ptdev->reclaim.lock);
> +
> +		freed += drm_gem_lru_scan(&vm->reclaim.lru, nr_to_scan - freed,
> +					  remaining, shrink, NULL);
> +
> +		mutex_lock(&ptdev->reclaim.lock);
> +
> +		/* If the VM is still in the temporary list, remove it so we
> +		 * can proceed with the next VM.
> +		 */
> +		if (vm->reclaim.lru_node.prev == &vms) {
> +			list_del_init(&vm->reclaim.lru_node);
> +
> +			/* Keep the VM around if there are still things to
> +			 * reclaim, so we can preserve the LRU order when
> +			 * re-inserting in ptdev->reclaim.vms at the end.
> +			 */
> +			if (vm->reclaim.lru.count > 0)
> +				list_add_tail(&vm->reclaim.lru_node, &remaining_vms);
> +		}
> +
> +		mutex_unlock(&ptdev->reclaim.lock);
> +
> +		panthor_vm_put(vm);
> +
> +		mutex_lock(&ptdev->reclaim.lock);
> +	}
> +
> +	/* Re-insert VMs with remaining data to reclaim at the beginning of
> +	 * the LRU. Note that any activeness change on the VM that happened
> +	 * while we were reclaiming would have moved the VM out of our
> +	 * temporary [remaining_]vms list, meaning anything we re-insert here
> +	 * preserves the LRU order.
> +	 */
> +	list_splice_tail(&vms, &remaining_vms);
> +	list_splice(&remaining_vms, &ptdev->reclaim.vms);
> +	mutex_unlock(&ptdev->reclaim.lock);
> +
> +	return freed;
>  }
>
>  /**
> diff --git a/drivers/gpu/drm/panthor/panthor_mmu.h b/drivers/gpu/drm/panthor/panthor_mmu.h
> index 0e268fdfdb2f..3522fbbce369 100644
> --- a/drivers/gpu/drm/panthor/panthor_mmu.h
> +++ b/drivers/gpu/drm/panthor/panthor_mmu.h
> @@ -1,6 +1,7 @@
>  /* SPDX-License-Identifier: GPL-2.0 or MIT */
>  /* Copyright 2019 Linaro, Ltd, Rob Herring <robh@kernel.org> */
>  /* Copyright 2023 Collabora ltd. */
> +/* Copyright 2025 ARM Limited. All rights reserved. */
>
>  #ifndef __PANTHOR_MMU_H__
>  #define __PANTHOR_MMU_H__
> @@ -46,6 +47,13 @@ struct panthor_vm *panthor_vm_create(struct panthor_device *ptdev, bool for_mcu,
>  				     u64 kernel_auto_va_start,
>  				     u64 kernel_auto_va_size);
>
> +void panthor_vm_update_bo_reclaim_lru_locked(struct panthor_gem_object *bo);
> +int panthor_vm_evict_bo_mappings_locked(struct panthor_gem_object *bo);
> +unsigned long
> +panthor_mmu_reclaim_priv_bos(struct panthor_device *ptdev,
> +			     unsigned int nr_to_scan, unsigned long *remaining,
> +			     bool (*shrink)(struct drm_gem_object *,
> +					    struct ww_acquire_ctx *));
>  int panthor_vm_prepare_mapped_bos_resvs(struct drm_exec *exec,
>  					struct panthor_vm *vm,
>  					u32 slot_count);
> --
> 2.53.0


Adrian Larumbe