Re: [PATCH 06/11] drm/xe: Create page reclaim list on unbind

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

On Tue, Nov 18, 2025 at 05:05:47PM +0800, Brian Nguyen wrote:
> Page reclaim list (PRL) is preparation work for the page reclaim feature.
> The PRL is firstly owned by pt_update_ops and all other page reclaim
> operations will point back to this PRL. PRL generates its entries during
> the unbind page walker, updating the PRL.
> 
> This PRL is restricted to a 4K page, so 512 page entries at most.
> 
> Signed-off-by: Brian Nguyen <brian3.nguyen@intel.com>
> ---
>  drivers/gpu/drm/xe/Makefile           |   1 +
>  drivers/gpu/drm/xe/regs/xe_gtt_defs.h |   1 +
>  drivers/gpu/drm/xe/xe_page_reclaim.c  |  52 ++++++++++++
>  drivers/gpu/drm/xe/xe_page_reclaim.h  |  49 ++++++++++++
>  drivers/gpu/drm/xe/xe_pt.c            | 109 ++++++++++++++++++++++++++
>  drivers/gpu/drm/xe/xe_pt_types.h      |   5 ++
>  6 files changed, 217 insertions(+)
>  create mode 100644 drivers/gpu/drm/xe/xe_page_reclaim.c
>  create mode 100644 drivers/gpu/drm/xe/xe_page_reclaim.h
> 
> diff --git a/drivers/gpu/drm/xe/Makefile b/drivers/gpu/drm/xe/Makefile
> index e4b273b025d2..048e6c93271c 100644
> --- a/drivers/gpu/drm/xe/Makefile
> +++ b/drivers/gpu/drm/xe/Makefile
> @@ -95,6 +95,7 @@ xe-y += xe_bb.o \
>  	xe_oa.o \
>  	xe_observation.o \
>  	xe_pagefault.o \
> +	xe_page_reclaim.o \
>  	xe_pat.o \
>  	xe_pci.o \
>  	xe_pcode.o \
> diff --git a/drivers/gpu/drm/xe/regs/xe_gtt_defs.h b/drivers/gpu/drm/xe/regs/xe_gtt_defs.h
> index 4389e5a76f89..4d83461e538b 100644
> --- a/drivers/gpu/drm/xe/regs/xe_gtt_defs.h
> +++ b/drivers/gpu/drm/xe/regs/xe_gtt_defs.h
> @@ -9,6 +9,7 @@
>  #define XELPG_GGTT_PTE_PAT0	BIT_ULL(52)
>  #define XELPG_GGTT_PTE_PAT1	BIT_ULL(53)
>  
> +#define XE_PTE_ADDR_MASK	GENMASK_ULL(51, 12)
>  #define GGTT_PTE_VFID		GENMASK_ULL(11, 2)
>  
>  #define GUC_GGTT_TOP		0xFEE00000
> diff --git a/drivers/gpu/drm/xe/xe_page_reclaim.c b/drivers/gpu/drm/xe/xe_page_reclaim.c
> new file mode 100644
> index 000000000000..a0d15efff58c
> --- /dev/null
> +++ b/drivers/gpu/drm/xe/xe_page_reclaim.c
> @@ -0,0 +1,52 @@
> +// SPDX-License-Identifier: MIT
> +/*
> + * Copyright © 2025 Intel Corporation
> + */
> +
> +#include <linux/bitfield.h>
> +#include <linux/kref.h>
> +#include <linux/mm.h>
> +#include <linux/slab.h>
> +
> +#include "xe_page_reclaim.h"
> +
> +#include "regs/xe_gt_regs.h"
> +#include "xe_assert.h"
> +#include "xe_macros.h"
> +
> +/**
> + * xe_page_reclaim_list_invalidate() - Mark a PRL as invalid
> + * @prl: Page reclaim list to reset
> + *
> + * Clears the entries pointer and marks the list as invalid so
> + * future use know PRL is unusable. It is expected that the entries
> + * have already been released.
> + */
> +void xe_page_reclaim_list_invalidate(struct xe_page_reclaim_list *prl)
> +{
> +	prl->entries = NULL;
> +	prl->num_entries = XE_PAGE_RECLAIM_INVALID_LIST;
> +}
> +
> +/**
> + * xe_page_reclaim_list_alloc_entries() - Allocate page reclaim list entries
> + * @prl: Page reclaim list to allocate entries for
> + *
> + * Allocate one 4K page for the PRL entries, otherwise assign prl->entries to NULL.
> + */
> +int xe_page_reclaim_list_alloc_entries(struct xe_page_reclaim_list *prl)
> +{
> +	struct page *page;
> +
> +	XE_WARN_ON(prl->entries != NULL);
> +	if (prl->entries)
> +		return 0;
> +
> +	page = alloc_page(GFP_KERNEL | __GFP_ZERO);
> +	if (page) {
> +		prl->entries = page_address(page);
> +		prl->num_entries = 0;
> +	}
> +
> +	return page ? 0 : -ENOMEM;
> +}
> diff --git a/drivers/gpu/drm/xe/xe_page_reclaim.h b/drivers/gpu/drm/xe/xe_page_reclaim.h
> new file mode 100644
> index 000000000000..d066d7d97f79
> --- /dev/null
> +++ b/drivers/gpu/drm/xe/xe_page_reclaim.h
> @@ -0,0 +1,49 @@
> +/* SPDX-License-Identifier: MIT */
> +/*
> + * Copyright © 2025 Intel Corporation
> + */
> +
> +#ifndef _XE_PAGE_RECLAIM_H_
> +#define _XE_PAGE_RECLAIM_H_
> +
> +#include <linux/kref.h>
> +#include <linux/mm.h>
> +#include <linux/slab.h>
> +#include <linux/types.h>
> +#include <linux/workqueue.h>
> +
> +#define XE_PAGE_RECLAIM_MAX_ENTRIES	512
> +#define XE_PAGE_RECLAIM_LIST_MAX_SIZE	SZ_4K
> +
> +struct xe_guc_page_reclaim_entry {
> +	u32 valid:1;
> +	u32 reclamation_size:6;
> +	u32 reserved:5;
> +	u32 address_lo:20;
> +	u32 address_hi:20;
> +	u32 reserved1:12;

This is wire interface with the GuC. Bitfields can based on endianess of
the CPU. I know this is a iGPU feature for now but it could possibly
change in the future, with that, to future proof can the layout of this
be setup via defines / macros? 

> +} __packed;
> +
> +struct xe_page_reclaim_list {
> +	/** @entries: array of page reclaim entries, page allocated */
> +	struct xe_guc_page_reclaim_entry *entries;
> +	/** @num_entries: number of entries */
> +	int num_entries;
> +#define XE_PAGE_RECLAIM_INVALID_LIST	-1
> +};
> +
> +void xe_page_reclaim_list_invalidate(struct xe_page_reclaim_list *prl);
> +int xe_page_reclaim_list_alloc_entries(struct xe_page_reclaim_list *prl);
> +static inline void xe_page_reclaim_entries_get(struct xe_guc_page_reclaim_entry *entries)
> +{
> +	if (entries)
> +		get_page(virt_to_page(entries));
> +}
> +
> +static inline void xe_page_reclaim_entries_put(struct xe_guc_page_reclaim_entry *entries)
> +{
> +	if (entries)
> +		put_page(virt_to_page(entries));
> +}

Kernel doc for static inlines.

> +
> +#endif	/* _XE_PAGE_RECLAIM_H_ */
> diff --git a/drivers/gpu/drm/xe/xe_pt.c b/drivers/gpu/drm/xe/xe_pt.c
> index 884127b4d97d..532a047676d4 100644
> --- a/drivers/gpu/drm/xe/xe_pt.c
> +++ b/drivers/gpu/drm/xe/xe_pt.c
> @@ -12,6 +12,7 @@
>  #include "xe_exec_queue.h"
>  #include "xe_gt.h"
>  #include "xe_migrate.h"
> +#include "xe_page_reclaim.h"
>  #include "xe_pt_types.h"
>  #include "xe_pt_walk.h"
>  #include "xe_res_cursor.h"
> @@ -1538,6 +1539,9 @@ struct xe_pt_stage_unbind_walk {
>  	/* Output */
>  	/* @wupd: Structure to track the page-table updates we're building */
>  	struct xe_walk_update wupd;
> +
> +	/** @prl: Backing pointer to page reclaim list in pt_update_ops */
> +	struct xe_page_reclaim_list *prl;
>  };
>  
>  /*
> @@ -1572,6 +1576,69 @@ static bool xe_pt_check_kill(u64 addr, u64 next, unsigned int level,
>  	return false;
>  }
>  
> +/* Huge 2MB leaf lives directly in a level-1 table and has no children */
> +static bool is_large_pte(struct xe_pt *pte)
> +{
> +	return pte->level == 1 && !pte->base.children;
> +}
> +
> +/* page_size = 2^(reclamation_size + 12) */
> +#define COMPUTE_RECLAIM_ADDRESS_MASK(page_size)				\
> +({									\
> +	BUILD_BUG_ON(!__builtin_constant_p(page_size));			\
> +	ilog2(page_size) - 12;						\

s/12/XE_PTE_SHIFT ?

> +})
> +
> +static void generate_reclaim_entry(struct xe_tile *tile,
> +				   struct xe_page_reclaim_list *prl,
> +				   u64 pte,
> +				   struct xe_pt *xe_child)

Nit, xe_pt can be on the same line as 'u64 pte'.

> +{
> +	struct xe_guc_page_reclaim_entry *reclaim_entries = prl->entries;
> +	u64 phys_addr = pte & XE_PTE_ADDR_MASK;
> +	const u64 field_mask = GENMASK_ULL(19, 0);
> +	u32 reclamation_size;

Nit, I'd make the last variable declared on the stack for readability. 

> +	const uint max_entries = XE_PAGE_RECLAIM_MAX_ENTRIES;
> +	int num_entries = prl->num_entries;
> +
> +	xe_tile_assert(tile, xe_child->level <= MAX_HUGEPTE_LEVEL);
> +	xe_tile_assert(tile, reclaim_entries);
> +
> +	if (num_entries == XE_PAGE_RECLAIM_INVALID_LIST)
> +		return;
> +
> +	/* Overflow: mark as invalid through num_entries */
> +	if (num_entries >= max_entries) {
> +		prl->num_entries = XE_PAGE_RECLAIM_INVALID_LIST;
> +		return;
> +	}
> +
> +	/**
> +	 * reclamation_size indicates the size of the page to be
> +	 * invalidated and flushed from non-coherent cache.
> +	 * Page size is computed as 2^(reclamation_size+12) bytes.
> +	 * Only valid for these specific levels.
> +	 */
> +
> +	if (xe_child->level == 0 && !(pte & XE_PTE_PS64))
> +		reclamation_size = COMPUTE_RECLAIM_ADDRESS_MASK(SZ_4K);  /* reclamation_size = 0 */
> +	else if (xe_child->level == 0)
> +		reclamation_size = COMPUTE_RECLAIM_ADDRESS_MASK(SZ_64K); /* reclamation_size = 1 */
> +	else if (is_large_pte(xe_child))
> +		reclamation_size = COMPUTE_RECLAIM_ADDRESS_MASK(SZ_2M);  /* reclamation_size = 2 */

What happens if we have 1G page? That doesn't seem to be handled.

> +	else
> +		return;
> +
> +	reclaim_entries[num_entries].valid = 1;
> +	reclaim_entries[num_entries].reclamation_size =
> +		reclamation_size;
> +	reclaim_entries[num_entries].address_lo =
> +		FIELD_GET(field_mask, phys_addr);
> +	reclaim_entries[num_entries].address_hi =
> +		FIELD_GET(field_mask, phys_addr >> 20);

As suggested above, use macros/defines here to setup the entry.

> +	prl->num_entries++;
> +}
> +
>  static int xe_pt_stage_unbind_entry(struct xe_ptw *parent, pgoff_t offset,
>  				    unsigned int level, u64 addr, u64 next,
>  				    struct xe_ptw **child,
> @@ -1579,10 +1646,27 @@ static int xe_pt_stage_unbind_entry(struct xe_ptw *parent, pgoff_t offset,
>  				    struct xe_pt_walk *walk)
>  {
>  	struct xe_pt *xe_child = container_of(*child, typeof(*xe_child), base);
> +	struct xe_pt_stage_unbind_walk *xe_walk =
> +		container_of(walk, typeof(*xe_walk), base);
> +	struct xe_device *xe = tile_to_xe(xe_walk->tile);
>  
>  	XE_WARN_ON(!*child);
>  	XE_WARN_ON(!level);
>  
> +	/* 4K and 64K Pages are level 0, large pte needs additional handling. */
> +	if (xe_walk->prl && (xe_child->level == 0 || is_large_pte(xe_child))) {

And also here? 1G pages are unhandled? Please explain.

> +		struct iosys_map *leaf_map = &xe_child->bo->vmap;
> +		pgoff_t first = xe_pt_offset(addr, 0, walk);
> +		pgoff_t count = xe_pt_num_entries(addr, next, 0, walk);
> +
> +		for (pgoff_t i = 0; i < count; i++) {
> +			u64 pte = xe_map_rd(xe, leaf_map, (first + i) * sizeof(u64), u64);
> +
> +			generate_reclaim_entry(xe_walk->tile, xe_walk->prl,
> +					       pte, xe_child);
> +		}
> +	}
> +
>  	xe_pt_check_kill(addr, next, level - 1, xe_child, action, walk);
>  
>  	return 0;
> @@ -1654,6 +1738,8 @@ static unsigned int xe_pt_stage_unbind(struct xe_tile *tile,
>  {
>  	u64 start = range ? xe_svm_range_start(range) : xe_vma_start(vma);
>  	u64 end = range ? xe_svm_range_end(range) : xe_vma_end(vma);
> +	struct xe_vm_pgtable_update_op *pt_update_op =
> +		container_of(entries, struct xe_vm_pgtable_update_op, entries[0]);
>  	struct xe_pt_stage_unbind_walk xe_walk = {
>  		.base = {
>  			.ops = &xe_pt_stage_unbind_ops,
> @@ -1665,6 +1751,7 @@ static unsigned int xe_pt_stage_unbind(struct xe_tile *tile,
>  		.modified_start = start,
>  		.modified_end = end,
>  		.wupd.entries = entries,
> +		.prl = pt_update_op->prl,
>  	};
>  	struct xe_pt *pt = vm->pt_root[tile->id];
>  
> @@ -1897,6 +1984,7 @@ static int unbind_op_prepare(struct xe_tile *tile,
>  			     struct xe_vm_pgtable_update_ops *pt_update_ops,
>  			     struct xe_vma *vma)
>  {
> +	struct xe_device *xe = tile_to_xe(tile);
>  	u32 current_op = pt_update_ops->current_op;
>  	struct xe_vm_pgtable_update_op *pt_op = &pt_update_ops->ops[current_op];
>  	int err;
> @@ -1914,6 +2002,13 @@ static int unbind_op_prepare(struct xe_tile *tile,
>  	pt_op->vma = vma;
>  	pt_op->bind = false;
>  	pt_op->rebind = false;
> +	/* Maintain one PRL located in pt_update_ops that all others in unbind op reference */
> +	if (xe->info.has_page_reclaim_hw_assist && !pt_update_ops->prl.entries) {
> +		err = xe_page_reclaim_list_alloc_entries(&pt_update_ops->prl);
> +		if (err < 0)
> +			xe_page_reclaim_list_invalidate(&pt_update_ops->prl);

I don't think you need to call xe_page_reclaim_list_invalidate, right?
If xe_page_reclaim_list_alloc_entries fails the prl should be in the
init state.

> +	}
> +	pt_op->prl = (pt_update_ops->prl.entries) ? &pt_update_ops->prl : NULL;
>  
>  	err = vma_reserve_fences(tile_to_xe(tile), vma);
>  	if (err)
> @@ -1921,6 +2016,13 @@ static int unbind_op_prepare(struct xe_tile *tile,
>  
>  	pt_op->num_entries = xe_pt_stage_unbind(tile, xe_vma_vm(vma),
>  						vma, NULL, pt_op->entries);
> +	/* Free PRL if list declared as invalid */
> +	if (pt_update_ops->prl.entries &&
> +	    pt_update_ops->prl.num_entries == XE_PAGE_RECLAIM_INVALID_LIST) {
> +		xe_page_reclaim_entries_put(pt_update_ops->prl.entries);
> +		pt_op->prl = NULL;
> +		pt_update_ops->prl.entries = NULL;

Call xe_page_reclaim_list_invalidate for clarity?

> +	}
>  
>  	xe_vm_dbg_print_entries(tile_to_xe(tile), pt_op->entries,
>  				pt_op->num_entries, false);
> @@ -1979,6 +2081,7 @@ static int unbind_range_prepare(struct xe_vm *vm,
>  	pt_op->vma = XE_INVALID_VMA;
>  	pt_op->bind = false;
>  	pt_op->rebind = false;
> +	pt_op->prl = NULL;
>  
>  	pt_op->num_entries = xe_pt_stage_unbind(tile, vm, NULL, range,
>  						pt_op->entries);
> @@ -2096,6 +2199,7 @@ xe_pt_update_ops_init(struct xe_vm_pgtable_update_ops *pt_update_ops)
>  	init_llist_head(&pt_update_ops->deferred);
>  	pt_update_ops->start = ~0x0ull;
>  	pt_update_ops->last = 0x0ull;
> +	xe_page_reclaim_list_invalidate(&pt_update_ops->prl);

Can we introduce a function called xe_page_reclaim_list_init for
clarity? It might do the same thing as xe_page_reclaim_list_invalidate
but it would make this a little more clear. Likewise later in the series
when a job is created, you can call xe_page_reclaim_list_init there too.

>  }
>  
>  /**
> @@ -2518,6 +2622,11 @@ void xe_pt_update_ops_fini(struct xe_tile *tile, struct xe_vma_ops *vops)
>  		&vops->pt_update_ops[tile->id];
>  	int i;
>  
> +	if (pt_update_ops->prl.entries) {
> +		xe_page_reclaim_entries_put(pt_update_ops->prl.entries);
> +		xe_page_reclaim_list_invalidate(&pt_update_ops->prl);
> +	}
> +
>  	lockdep_assert_held(&vops->vm->lock);
>  	xe_vm_assert_held(vops->vm);
>  
> diff --git a/drivers/gpu/drm/xe/xe_pt_types.h b/drivers/gpu/drm/xe/xe_pt_types.h
> index 881f01e14db8..26e5295f118e 100644
> --- a/drivers/gpu/drm/xe/xe_pt_types.h
> +++ b/drivers/gpu/drm/xe/xe_pt_types.h
> @@ -8,6 +8,7 @@
>  
>  #include <linux/types.h>
>  
> +#include "xe_page_reclaim.h"
>  #include "xe_pt_walk.h"
>  
>  struct xe_bo;
> @@ -85,6 +86,8 @@ struct xe_vm_pgtable_update_op {
>  	bool bind;
>  	/** @rebind: is a rebind */
>  	bool rebind;
> +	/** @prl: Backing pointer to page reclaim list of pt_update_ops */
> +	struct xe_page_reclaim_list *prl;

Can you move this above the bools in the layout of
xe_vm_pgtable_update_op, likely just below "struct xe_vma".

>  };
>  
>  /** struct xe_vm_pgtable_update_ops: page table update operations */
> @@ -119,6 +122,8 @@ struct xe_vm_pgtable_update_ops {
>  	 * slots are idle.
>  	 */
>  	bool wait_vm_kernel;
> +	/** @prl: embedded page reclaim list */
> +	struct xe_page_reclaim_list prl;

Same thing here, move just below "struct xe_exec_queue".

Matt

>  };
>  
>  #endif
> -- 
> 2.51.2
>