drm/xe: Create page reclaim list on unbind

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.

v2:
 - Removed unused function. (Shuicheng)
 - Compacted warning checking, update commit message,
   spelling, etc. (Shuicheng, Matthew B)
 - Fix kernel docs
 - Moved PRL max entries overflow handling out from
   generate_reclaim_entry to caller (Shuicheng)
 - Add xe_page_reclaim_list_init for clarity. (Matthew B)
 - Modify xe_guc_page_reclaim_entry to use macros
   for greater flexbility. (Matthew B)
 - Add fallback for PTE outside of page reclaim supported
   4K, 64K, 2M pages (Matthew B)
 - Invalidate PRL for early abort page walk.
 - Removed page reclaim related variables from tlb fence
   (Matthew Brost)
 - Remove error handling in *alloc_entries failure. (Matthew B)

v3:
 - Fix NULL pointer dereference check.
 - Modify reclaim_entry to QW and bitfields accordingly. (Matthew B)
 - Add vm_dbg prints for PRL generation and invalidation. (Matthew B)

v4:
 - s/GENMASK/GENMASK_ULL && s/BIT/BIT_ULL (CI)

v5:
 - Addition of xe_page_reclaim_list_is_new() to avoid continuous
   allocation of PRL if consecutive VMAs cause a PRL invalidation.
 - Add xe_page_reclaim_list_valid() helpers for clarity. (Matthew B)
 - Move xe_page_reclaim_list_entries_put in
   xe_page_reclaim_list_invalidate.

Signed-off-by: Brian Nguyen <brian3.nguyen@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Cc: Shuicheng Lin <shuicheng.lin@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patch.msgid.link/20251212213225.3564537-17-brian3.nguyen@intel.com

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 \

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

drivers/gpu/drm/xe/xe_page_reclaim.c

@@ -0,0 +1,65 @@
+// 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 knows 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)
+{
+	xe_page_reclaim_entries_put(prl->entries);
+	prl->entries = NULL;
+	prl->num_entries = XE_PAGE_RECLAIM_INVALID_LIST;
+}
+
+/**
+ * xe_page_reclaim_list_init() - Initialize a page reclaim list
+ * @prl: Page reclaim list to initialize
+ *
+ * NULLs both values in list to prepare on initalization.
+ */
+void xe_page_reclaim_list_init(struct xe_page_reclaim_list *prl)
+{
+	// xe_page_reclaim_list_invalidate(prl);
+	prl->entries = NULL;
+	prl->num_entries = 0;
+}
+
+/**
+ * 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;
+
+	if (XE_WARN_ON(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;
+}

drivers/gpu/drm/xe/xe_page_reclaim.h

@@ -0,0 +1,96 @@
+/* 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>
+#include <linux/bits.h>
+
+#define XE_PAGE_RECLAIM_MAX_ENTRIES	512
+#define XE_PAGE_RECLAIM_LIST_MAX_SIZE	SZ_4K
+
+struct xe_guc_page_reclaim_entry {
+	u64 qw;
+/* valid reclaim entry bit */
+#define XE_PAGE_RECLAIM_VALID		BIT_ULL(0)
+/*
+ * offset order of page size to be reclaimed
+ * page_size = 1 << (XE_PTE_SHIFT + reclamation_size)
+ */
+#define XE_PAGE_RECLAIM_SIZE		GENMASK_ULL(6, 1)
+#define XE_PAGE_RECLAIM_RSVD_0		GENMASK_ULL(11, 7)
+/* lower 20 bits of the physical address */
+#define XE_PAGE_RECLAIM_ADDR_LO		GENMASK_ULL(31, 12)
+/* upper 20 bits of the physical address */
+#define XE_PAGE_RECLAIM_ADDR_HI		GENMASK_ULL(51, 32)
+#define XE_PAGE_RECLAIM_RSVD_1		GENMASK_ULL(63, 52)
+} __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
+};
+
+/**
+ * xe_page_reclaim_list_is_new() - Check if PRL is new allocation
+ * @prl: Pointer to page reclaim list
+ *
+ * PRL indicates it hasn't been allocated through both values being NULL
+ */
+static inline bool xe_page_reclaim_list_is_new(struct xe_page_reclaim_list *prl)
+{
+	return !prl->entries && prl->num_entries == 0;
+}
+
+/**
+ * xe_page_reclaim_list_valid() - Check if the page reclaim list is valid
+ * @prl: Pointer to page reclaim list
+ *
+ * PRL uses the XE_PAGE_RECLAIM_INVALID_LIST to indicate that a PRL
+ * is unusable.
+ */
+static inline bool xe_page_reclaim_list_valid(struct xe_page_reclaim_list *prl)
+{
+	return !xe_page_reclaim_list_is_new(prl) &&
+	       prl->num_entries != XE_PAGE_RECLAIM_INVALID_LIST;
+}
+
+void xe_page_reclaim_list_invalidate(struct xe_page_reclaim_list *prl);
+void xe_page_reclaim_list_init(struct xe_page_reclaim_list *prl);
+int xe_page_reclaim_list_alloc_entries(struct xe_page_reclaim_list *prl);
+/**
+ * xe_page_reclaim_entries_get() - Increment the reference count of page reclaim entries.
+ * @entries: Pointer to the array of page reclaim entries.
+ *
+ * This function increments the reference count of the backing page.
+ */
+static inline void xe_page_reclaim_entries_get(struct xe_guc_page_reclaim_entry *entries)
+{
+	if (entries)
+		get_page(virt_to_page(entries));
+}
+
+/**
+ * xe_page_reclaim_entries_put() - Decrement the reference count of page reclaim entries.
+ * @entries: Pointer to the array of page reclaim entries.
+ *
+ * This function decrements the reference count of the backing page
+ * and frees it if the count reaches zero.
+ */
+static inline void xe_page_reclaim_entries_put(struct xe_guc_page_reclaim_entry *entries)
+{
+	if (entries)
+		put_page(virt_to_page(entries));
+}
+
+#endif	/* _XE_PAGE_RECLAIM_H_ */

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"
@@ -1535,6 +1536,9 @@ struct xe_pt_stage_unbind_walk {
 	/** @modified_end: Walk range start, modified like @modified_start. */
 	u64 modified_end;
 
+	/** @prl: Backing pointer to page reclaim list in pt_update_ops */
+	struct xe_page_reclaim_list *prl;
+
 	/* Output */
 	/* @wupd: Structure to track the page-table updates we're building */
 	struct xe_walk_update wupd;
@@ -1572,6 +1576,68 @@ 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_2m_pte(struct xe_pt *pte)
+{
+	return pte->level == 1 && !pte->base.children;
+}
+
+/* page_size = 2^(reclamation_size + XE_PTE_SHIFT) */
+#define COMPUTE_RECLAIM_ADDRESS_MASK(page_size)				\
+({									\
+	BUILD_BUG_ON(!__builtin_constant_p(page_size));			\
+	ilog2(page_size) - XE_PTE_SHIFT;				\
+})
+
+static int generate_reclaim_entry(struct xe_tile *tile,
+				  struct xe_page_reclaim_list *prl,
+				  u64 pte, struct xe_pt *xe_child)
+{
+	struct xe_guc_page_reclaim_entry *reclaim_entries = prl->entries;
+	u64 phys_page = (pte & XE_PTE_ADDR_MASK) >> XE_PTE_SHIFT;
+	int num_entries = prl->num_entries;
+	u32 reclamation_size;
+
+	xe_tile_assert(tile, xe_child->level <= MAX_HUGEPTE_LEVEL);
+	xe_tile_assert(tile, reclaim_entries);
+	xe_tile_assert(tile, num_entries < XE_PAGE_RECLAIM_MAX_ENTRIES - 1);
+
+	if (!xe_page_reclaim_list_valid(prl))
+		return -EINVAL;
+
+	/**
+	 * 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 + XE_PTE_SHIFT) bytes.
+	 * Only 4K, 64K (level 0), and 2M pages are supported by hardware for page reclaim
+	 */
+	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 = 4 */
+	} else if (is_2m_pte(xe_child)) {
+		reclamation_size = COMPUTE_RECLAIM_ADDRESS_MASK(SZ_2M);  /* reclamation_size = 9 */
+	} else {
+		xe_page_reclaim_list_invalidate(prl);
+		vm_dbg(&tile_to_xe(tile)->drm,
+		       "PRL invalidate: unsupported PTE level=%u pte=%#llx\n",
+		       xe_child->level, pte);
+		return -EINVAL;
+	}
+
+	reclaim_entries[num_entries].qw =
+		FIELD_PREP(XE_PAGE_RECLAIM_VALID, 1) |
+		FIELD_PREP(XE_PAGE_RECLAIM_SIZE, reclamation_size) |
+		FIELD_PREP(XE_PAGE_RECLAIM_ADDR_LO, phys_page) |
+		FIELD_PREP(XE_PAGE_RECLAIM_ADDR_HI, phys_page >> 20);
+	prl->num_entries++;
+	vm_dbg(&tile_to_xe(tile)->drm,
+	       "PRL add entry: level=%u pte=%#llx reclamation_size=%u prl_idx=%d\n",
+	       xe_child->level, pte, reclamation_size, num_entries);
+
+	return 0;
+}
+
 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,
@@ -1579,11 +1645,48 @@ 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);
+	/* Check for leaf node */
+	if (xe_walk->prl && xe_page_reclaim_list_valid(xe_walk->prl) &&
+	    !xe_child->base.children) {
+		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);
 
-	xe_pt_check_kill(addr, next, level - 1, xe_child, action, walk);
+		for (pgoff_t i = 0; i < count; i++) {
+			u64 pte = xe_map_rd(xe, leaf_map, (first + i) * sizeof(u64), u64);
+			int ret;
+
+			/* Account for NULL terminated entry on end (-1) */
+			if (xe_walk->prl->num_entries < XE_PAGE_RECLAIM_MAX_ENTRIES - 1) {
+				ret = generate_reclaim_entry(xe_walk->tile, xe_walk->prl,
+							     pte, xe_child);
+				if (ret)
+					break;
+			} else {
+				/* overflow, mark as invalid */
+				xe_page_reclaim_list_invalidate(xe_walk->prl);
+				vm_dbg(&xe->drm,
+				       "PRL invalidate: overflow while adding pte=%#llx",
+				       pte);
+				break;
+			}
+		}
+	}
+
+	/* If aborting page walk early, invalidate PRL since PTE may be dropped from this abort */
+	if (xe_pt_check_kill(addr, next, level - 1, xe_child, action, walk) &&
+	    xe_walk->prl && level > 1 && xe_child->base.children && xe_child->num_live != 0) {
+		xe_page_reclaim_list_invalidate(xe_walk->prl);
+		vm_dbg(&xe->drm,
+		       "PRL invalidate: kill at level=%u addr=%#llx next=%#llx num_live=%u\n",
+		       level, addr, next, xe_child->num_live);
+	}
 
 	return 0;
 }
@@ -1654,6 +1757,8 @@ 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 +1770,7 @@ 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 +2003,7 @@ 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 +2021,16 @@ 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.
+	 * Ensure that PRL is allocated only once, and if invalidated, remains an invalidated PRL.
+	 */
+	if (xe->info.has_page_reclaim_hw_assist &&
+	    xe_page_reclaim_list_is_new(&pt_update_ops->prl))
+		xe_page_reclaim_list_alloc_entries(&pt_update_ops->prl);
+
+	/* Page reclaim may not be needed due to other features, so skip the corresponding VMA */
+	pt_op->prl = (xe_page_reclaim_list_valid(&pt_update_ops->prl)) ? &pt_update_ops->prl : NULL;
 
 	err = vma_reserve_fences(tile_to_xe(tile), vma);
 	if (err)
@@ -1979,6 +2096,7 @@ 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 +2214,7 @@ 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_init(&pt_update_ops->prl);
 }
 
 /**
@@ -2518,6 +2637,8 @@ void xe_pt_update_ops_fini(struct xe_tile *tile, struct xe_vma_ops *vops)
 		&vops->pt_update_ops[tile->id];
 	int i;
 
+	xe_page_reclaim_entries_put(pt_update_ops->prl.entries);
+
 	lockdep_assert_held(&vops->vm->lock);
 	xe_vm_assert_held(vops->vm);
 

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;
@@ -79,6 +80,8 @@ struct xe_vm_pgtable_update_op {
 	struct xe_vm_pgtable_update entries[XE_VM_MAX_LEVEL * 2 + 1];
 	/** @vma: VMA for operation, operation not valid if NULL */
 	struct xe_vma *vma;
+	/** @prl: Backing pointer to page reclaim list of pt_update_ops */
+	struct xe_page_reclaim_list *prl;
 	/** @num_entries: number of entries for this update operation */
 	u32 num_entries;
 	/** @bind: is a bind */
@@ -95,6 +98,8 @@ struct xe_vm_pgtable_update_ops {
 	struct llist_head deferred;
 	/** @q: exec queue for PT operations */
 	struct xe_exec_queue *q;
+	/** @prl: embedded page reclaim list */
+	struct xe_page_reclaim_list prl;
 	/** @start: start address of ops */
 	u64 start;
 	/** @last: last address of ops */