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arm64: mte: simplify swap tag restoration logic 

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@google.com
Link: https://linux-review.googlesource.com/id/I8ad54476f3b2d0144ccd8ce0c1d7a2963e5ff6f3
Signed-off-by: Peter Collingbourne <pcc@google.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Alexandru Elisei <alexandru.elisei@arm.com>
Cc: Chinwen Chang <chinwen.chang@mediatek.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: kasan-dev@googlegroups.com
Cc: kasan-dev <kasan-dev@googlegroups.com>
Cc: "Kuan-Ying Lee (李冠穎)" <Kuan-Ying.Lee@mediatek.com>
Cc: Qun-Wei Lin <qun-wei.lin@mediatek.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: "Huang, Ying" <ying.huang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Peter Collingbourne 2023-05-22 17:43:10 -07:00 committed by Andrew Morton
parent b53e24c4f6
commit 332c151c71
3 changed files with 11 additions and 44 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
arch/arm64/include/asm/mte.h
View File

@ -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)

14
arch/arm64/include/asm/pgtable.h
View File

@ -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);

37
arch/arm64/kernel/mte.c
View File

@ -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();