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Message-Id: <20230523004312.1807357-4-pcc@google.com>
Date: Mon, 22 May 2023 17:43:10 -0700
From: Peter Collingbourne <pcc@...gle.com>
To: Catalin Marinas <catalin.marinas@....com>
Cc: Peter Collingbourne <pcc@...gle.com>,
"Qun-wei Lin (林群崴)"
<Qun-wei.Lin@...iatek.com>, linux-arm-kernel@...ts.infradead.org,
linux-mm@...ck.org, linux-kernel@...r.kernel.org,
"surenb@...gle.com" <surenb@...gle.com>,
"david@...hat.com" <david@...hat.com>,
"Chinwen Chang (張錦文)"
<chinwen.chang@...iatek.com>,
"kasan-dev@...glegroups.com" <kasan-dev@...glegroups.com>,
"Kuan-Ying Lee (李冠穎)"
<Kuan-Ying.Lee@...iatek.com>,
"Casper Li (李中榮)"
<casper.li@...iatek.com>,
"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
vincenzo.frascino@....com,
Alexandru Elisei <alexandru.elisei@....com>, will@...nel.org,
eugenis@...gle.com, Steven Price <steven.price@....com>
Subject: [PATCH v4 3/3] arm64: mte: Simplify swap tag restoration logic
As a result of the previous two patches, 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.
Signed-off-by: Peter Collingbourne <pcc@...gle.com>
Link: https://linux-review.googlesource.com/id/I8ad54476f3b2d0144ccd8ce0c1d7a2963e5ff6f3
Reviewed-by: Steven Price <steven.price@....com>
Reviewed-by: Catalin Marinas <catalin.marinas@....com>
---
v4:
- Rebased onto v6.4-rc3
- Reverted change to arch/arm64/mm/mteswap.c; this change was not
valid because swapcache pages can have arch_swap_restore() called
on them multiple times
v3:
- Rebased onto arm64/for-next/fixes, which already has a fix
for the issue previously tagged, therefore removed Fixes:
tag
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(-)
diff --git a/arch/arm64/include/asm/mte.h b/arch/arm64/include/asm/mte.h
index c028afb1cd0b..4cedbaa16f41 100644
--- a/arch/arm64/include/asm/mte.h
+++ b/arch/arm64/include/asm/mte.h
@@ -90,7 +90,7 @@ static inline bool try_page_mte_tagging(struct page *page)
}
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(struct page *page)
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)
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 0bd18de9fd97..e8a252e62b12 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -337,18 +337,8 @@ static inline void __set_pte_at(struct mm_struct *mm, unsigned long addr,
* 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);
diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
index 7e89968bd282..c40728046fed 100644
--- a/arch/arm64/kernel/mte.c
+++ b/arch/arm64/kernel/mte.c
@@ -35,41 +35,18 @@ DEFINE_STATIC_KEY_FALSE(mte_async_or_asymm_mode);
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();
--
2.40.1.698.g37aff9b760-goog
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