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BACKPORT: FROMLIST: arm64: mte: Simplify swap tag restoration logic

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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@google.com>
Link: https://linux-review.googlesource.com/id/I8ad54476f3b2d0144ccd8ce0c1d7a2963e5ff6f3
Reviewed-by: Steven Price <steven.price@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/all/20230523004312.1807357-4-pcc@google.com/
Change-Id: I8ad54476f3b2d0144ccd8ce0c1d7a2963e5ff6f3
[pcc: resolved merge conflict]
Bug: 274890466
This commit is contained in:
Peter Collingbourne 2023-05-12 12:08:01 -07:00
parent 131714e34b
commit c0cfeeaa88
4 changed files with 18 additions and 59 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
arch/arm64/include/asm/mte.h
View File

@ -25,7 +25,7 @@ unsigned long mte_copy_tags_to_user(void __user *to, void *from,
unsigned long n);
int mte_save_tags(struct page *page);
void mte_save_page_tags(const void *page_addr, void *tag_storage);
bool mte_restore_tags(swp_entry_t entry, struct page *page);
void mte_restore_tags(swp_entry_t entry, struct page *page);
void mte_restore_page_tags(void *page_addr, const void *tag_storage);
void mte_invalidate_tags(int type, pgoff_t offset);
void mte_invalidate_tags_area(int type);
@ -61,7 +61,7 @@ static inline bool page_mte_tagged(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);
@ -89,7 +89,7 @@ static inline bool page_mte_tagged(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)

18
arch/arm64/include/asm/pgtable.h
View File

@ -335,18 +335,8 @@ 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_racy_pte_update(mm, ptep, pte);
@ -1066,8 +1056,8 @@ static inline void arch_swap_invalidate_area(int type)
#define __HAVE_ARCH_SWAP_RESTORE
static inline void arch_swap_restore(swp_entry_t entry, struct folio *folio)
{
if (system_supports_mte() && mte_restore_tags(entry, &folio->page))
set_page_mte_tagged(&folio->page);
if (system_supports_mte())
mte_restore_tags(entry, &folio->page);
}
#endif /* CONFIG_ARM64_MTE */

43
arch/arm64/kernel/mte.c
View File

@ -35,47 +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)) {
set_page_mte_tagged(page);
return;
}
}
if (!pte_is_tagged)
return;
/*
* Test PG_mte_tagged again in case it was racing with another
* set_pte_at().
*/
if (!page_mte_tagged(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 (!page_mte_tagged(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();

10
arch/arm64/mm/mteswap.c
View File

@ -46,21 +46,19 @@ int mte_save_tags(struct page *page)
return 0;
}
bool mte_restore_tags(swp_entry_t entry, struct page *page)
void mte_restore_tags(swp_entry_t entry, struct page *page)
{
void *tags = xa_load(&mte_pages, entry.val);
if (!tags)
return false;
return;
/*
* Test PG_mte_tagged again in case it was racing with another
* set_pte_at().
* Test PG_mte_tagged in case the tags were restored before
* (e.g. CoW pages).
*/
if (!test_and_set_bit(PG_mte_tagged, &page->flags))
mte_restore_page_tags(page_address(page), tags);
return true;
}
void mte_invalidate_tags(int type, pgoff_t offset)