The patch titled
Subject: arm64: mte: simplify swap tag restoration logic
has been added to the -mm mm-unstable branch. Its filename is
arm64-mte-simplify-swap-tag-restoration-logic.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/arm64-mte-simplify-swap-tag-restoration-logic.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Peter Collingbourne <pcc@xxxxxxxxxx>
Subject: arm64: mte: simplify swap tag restoration logic
Date: Mon, 22 May 2023 17:43:10 -0700
As a result of the patches "mm: Call arch_swap_restore() from
do_swap_page()" and "mm: Call arch_swap_restore() from unuse_pte()", there
are no circumstances in which a swapped-in page is installed in a page
table without first having arch_swap_restore() called on it. Therefore,
we no longer need the logic in set_pte_at() that restores the tags, so
remove it.
Link: https://lkml.kernel.org/r/20230523004312.1807357-4-pcc@xxxxxxxxxx
Link: https://linux-review.googlesource.com/id/I8ad54476f3b2d0144ccd8ce0c1d7a2963e5ff6f3
Signed-off-by: Peter Collingbourne <pcc@xxxxxxxxxx>
Reviewed-by: Steven Price <steven.price@xxxxxxx>
Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Alexandru Elisei <alexandru.elisei@xxxxxxx>
Cc: Chinwen Chang <chinwen.chang@xxxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Evgenii Stepanov <eugenis@xxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: kasan-dev@xxxxxxxxxxxxxxxx
Cc: kasan-dev <kasan-dev@xxxxxxxxxxxxxxxx>
Cc: "Kuan-Ying Lee (æ??å? ç©?)" <Kuan-Ying.Lee@xxxxxxxxxxxx>
Cc: Qun-Wei Lin <qun-wei.lin@xxxxxxxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: "Huang, Ying" <ying.huang@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/arm64/include/asm/mte.h | 4 +--
arch/arm64/include/asm/pgtable.h | 14 +---------
arch/arm64/kernel/mte.c | 37 +++++------------------------
3 files changed, 11 insertions(+), 44 deletions(-)
--- a/arch/arm64/include/asm/mte.h~arm64-mte-simplify-swap-tag-restoration-logic
+++ a/arch/arm64/include/asm/mte.h
@@ -90,7 +90,7 @@ static inline bool try_page_mte_tagging(
}
void mte_zero_clear_page_tags(void *addr);
-void mte_sync_tags(pte_t old_pte, pte_t pte);
+void mte_sync_tags(pte_t pte);
void mte_copy_page_tags(void *kto, const void *kfrom);
void mte_thread_init_user(void);
void mte_thread_switch(struct task_struct *next);
@@ -122,7 +122,7 @@ static inline bool try_page_mte_tagging(
static inline void mte_zero_clear_page_tags(void *addr)
{
}
-static inline void mte_sync_tags(pte_t old_pte, pte_t pte)
+static inline void mte_sync_tags(pte_t pte)
{
}
static inline void mte_copy_page_tags(void *kto, const void *kfrom)
--- a/arch/arm64/include/asm/pgtable.h~arm64-mte-simplify-swap-tag-restoration-logic
+++ a/arch/arm64/include/asm/pgtable.h
@@ -337,18 +337,8 @@ static inline void __set_pte_at(struct m
* don't expose tags (instruction fetches don't check tags).
*/
if (system_supports_mte() && pte_access_permitted(pte, false) &&
- !pte_special(pte)) {
- pte_t old_pte = READ_ONCE(*ptep);
- /*
- * We only need to synchronise if the new PTE has tags enabled
- * or if swapping in (in which case another mapping may have
- * set tags in the past even if this PTE isn't tagged).
- * (!pte_none() && !pte_present()) is an open coded version of
- * is_swap_pte()
- */
- if (pte_tagged(pte) || (!pte_none(old_pte) && !pte_present(old_pte)))
- mte_sync_tags(old_pte, pte);
- }
+ !pte_special(pte) && pte_tagged(pte))
+ mte_sync_tags(pte);
__check_safe_pte_update(mm, ptep, pte);
--- a/arch/arm64/kernel/mte.c~arm64-mte-simplify-swap-tag-restoration-logic
+++ a/arch/arm64/kernel/mte.c
@@ -35,41 +35,18 @@ DEFINE_STATIC_KEY_FALSE(mte_async_or_asy
EXPORT_SYMBOL_GPL(mte_async_or_asymm_mode);
#endif
-static void mte_sync_page_tags(struct page *page, pte_t old_pte,
- bool check_swap, bool pte_is_tagged)
-{
- if (check_swap && is_swap_pte(old_pte)) {
- swp_entry_t entry = pte_to_swp_entry(old_pte);
-
- if (!non_swap_entry(entry))
- mte_restore_tags(entry, page);
- }
-
- if (!pte_is_tagged)
- return;
-
- if (try_page_mte_tagging(page)) {
- mte_clear_page_tags(page_address(page));
- set_page_mte_tagged(page);
- }
-}
-
-void mte_sync_tags(pte_t old_pte, pte_t pte)
+void mte_sync_tags(pte_t pte)
{
struct page *page = pte_page(pte);
long i, nr_pages = compound_nr(page);
- bool check_swap = nr_pages == 1;
- bool pte_is_tagged = pte_tagged(pte);
-
- /* Early out if there's nothing to do */
- if (!check_swap && !pte_is_tagged)
- return;
/* if PG_mte_tagged is set, tags have already been initialised */
- for (i = 0; i < nr_pages; i++, page++)
- if (!page_mte_tagged(page))
- mte_sync_page_tags(page, old_pte, check_swap,
- pte_is_tagged);
+ for (i = 0; i < nr_pages; i++, page++) {
+ if (try_page_mte_tagging(page)) {
+ mte_clear_page_tags(page_address(page));
+ set_page_mte_tagged(page);
+ }
+ }
/* ensure the tags are visible before the PTE is set */
smp_wmb();
_
Patches currently in -mm which might be from pcc@xxxxxxxxxx are
mm-call-arch_swap_restore-from-do_swap_page.patch
mm-call-arch_swap_restore-from-unuse_pte.patch
arm64-mte-simplify-swap-tag-restoration-logic.patch
