[PATCH RFC v2 21/27] mm: arm64: Handle tag storage pages mapped before mprotect(PROT_MTE)

Alexandru Elisei
2023-11-19T17:00:09Z

Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
---
arch/arm64/include/asm/mte_tag_storage.h | 1 +
arch/arm64/kernel/mte_tag_storage.c | 15 +++++++
arch/arm64/mm/fault.c | 55 ++++++++++++++++++++++++
include/linux/migrate.h | 8 +++-
include/linux/migrate_mode.h | 1 +
mm/internal.h | 6 ---
6 files changed, 78 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/include/asm/mte_tag_storage.h b/arch/arm64/include/asm/mte_tag_storage.h
index b97406d369ce..6a8b19a6a758 100644
--- a/arch/arm64/include/asm/mte_tag_storage.h
+++ b/arch/arm64/include/asm/mte_tag_storage.h
@@ -33,6 +33,7 @@ int reserve_tag_storage(struct page *page, int order, gfp_t gfp);
void free_tag_storage(struct page *page, int order);

bool page_tag_storage_reserved(struct page *page);
+bool page_is_tag_storage(struct page *page);

vm_fault_t handle_page_missing_tag_storage(struct vm_fault *vmf);
vm_fault_t handle_huge_page_missing_tag_storage(struct vm_fault *vmf);
diff --git a/arch/arm64/kernel/mte_tag_storage.c b/arch/arm64/kernel/mte_tag_storage.c
index a1cc239f7211..5096ce859136 100644
--- a/arch/arm64/kernel/mte_tag_storage.c
+++ b/arch/arm64/kernel/mte_tag_storage.c
@@ -500,6 +500,21 @@ bool page_tag_storage_reserved(struct page *page)
return test_bit(PG_tag_storage_reserved, &page->flags);
}

+bool page_is_tag_storage(struct page *page)
+{
+ unsigned long pfn = page_to_pfn(page);
+ struct range *tag_range;
+ int i;
+
+ for (i = 0; i < num_tag_regions; i++) {
+ tag_range = &tag_regions[i].tag_range;
+ if (tag_range->start <= pfn && pfn <= tag_range->end)
+ return true;
+ }
+
+ return false;
+}
+
int reserve_tag_storage(struct page *page, int order, gfp_t gfp)
{
unsigned long start_block, end_block;
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 6730a0812a24..964c5ae161a3 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -12,6 +12,7 @@
#include <linux/extable.h>
#include <linux/kfence.h>
#include <linux/signal.h>
+#include <linux/migrate.h>
#include <linux/mm.h>
#include <linux/hardirq.h>
#include <linux/init.h>
@@ -956,6 +957,50 @@ void tag_clear_highpage(struct page *page)
}

#ifdef CONFIG_ARM64_MTE_TAG_STORAGE
+
+#define MR_TAGGED_TAG_STORAGE MR_ARCH_1
+
+extern bool isolate_lru_page(struct page *page);
+extern void putback_movable_pages(struct list_head *l);
+
+/* Returns with the page reference dropped. */
+static void migrate_tag_storage_page(struct page *page)
+{
+ struct migration_target_control mtc = {
+ .nid = NUMA_NO_NODE,
+ .gfp_mask = GFP_HIGHUSER_MOVABLE | __GFP_TAGGED,
+ };
+ unsigned long i, nr_pages = compound_nr(page);
+ LIST_HEAD(pagelist);
+ int ret, tries;
+
+ lru_cache_disable();
+
+ for (i = 0; i < nr_pages; i++) {
+ if (!isolate_lru_page(page + i)) {
+ ret = -EAGAIN;
+ goto out;
+ }
+ /* Isolate just grabbed another reference, drop ours. */
+ put_page(page + i);
+ list_add_tail(&(page + i)->lru, &pagelist);
+ }
+
+ tries = 5;
+ while (tries--) {
+ ret = migrate_pages(&pagelist, alloc_migration_target, NULL, (unsigned long)&mtc,
+ MIGRATE_SYNC, MR_TAGGED_TAG_STORAGE, NULL);
+ if (ret == 0 || ret != -EBUSY)
+ break;
+ }
+
+out:
+ if (ret != 0)
+ putback_movable_pages(&pagelist);
+
+ lru_cache_enable();
+}
+
vm_fault_t handle_page_missing_tag_storage(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
@@ -1013,6 +1058,11 @@ vm_fault_t handle_page_missing_tag_storage(struct vm_fault *vmf)
if (unlikely(is_migrate_isolate_page(page)))
goto out_retry;

+ if (unlikely(page_is_tag_storage(page))) {
+ migrate_tag_storage_page(page);
+ return 0;
+ }
+
ret = reserve_tag_storage(page, 0, GFP_HIGHUSER_MOVABLE);
if (ret)
goto out_retry;
@@ -1098,6 +1148,11 @@ vm_fault_t handle_huge_page_missing_tag_storage(struct vm_fault *vmf)
if (unlikely(is_migrate_isolate_page(page)))
goto out_retry;

+ if (unlikely(page_is_tag_storage(page))) {
+ migrate_tag_storage_page(page);
+ return 0;
+ }
+
ret = reserve_tag_storage(page, HPAGE_PMD_ORDER, GFP_HIGHUSER_MOVABLE);
if (ret)
goto out_retry;
diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index 0acef592043c..afca42ace735 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -10,8 +10,6 @@
typedef struct folio *new_folio_t(struct folio *folio, unsigned long private);
typedef void free_folio_t(struct folio *folio, unsigned long private);

-struct migration_target_control;
-
/*
* Return values from addresss_space_operations.migratepage():
* - negative errno on page migration failure;
@@ -57,6 +55,12 @@ struct movable_operations {
void (*putback_page)(struct page *);
};

+struct migration_target_control {
+ int nid; /* preferred node id */
+ nodemask_t *nmask;
+ gfp_t gfp_mask;
+};
+
/* Defined in mm/debug.c: */
extern const char *migrate_reason_names[MR_TYPES];

diff --git a/include/linux/migrate_mode.h b/include/linux/migrate_mode.h
index f37cc03f9369..c6c5c7726d26 100644
--- a/include/linux/migrate_mode.h
+++ b/include/linux/migrate_mode.h
@@ -29,6 +29,7 @@ enum migrate_reason {
MR_CONTIG_RANGE,
MR_LONGTERM_PIN,
MR_DEMOTION,
+ MR_ARCH_1,
MR_TYPES
};

diff --git a/mm/internal.h b/mm/internal.h
index ddf6bb6c6308..96fff5dfc041 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -949,12 +949,6 @@ static inline bool is_migrate_highatomic_page(struct page *page)

void setup_zone_pageset(struct zone *zone);

-struct migration_target_control {
- int nid; /* preferred node id */
- nodemask_t *nmask;
- gfp_t gfp_mask;
-};
-
/*
* mm/filemap.c
*/
--
2.42.1