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Tue, 16 May 2023 19:21:29 -0700 (PDT) Date: Tue, 16 May 2023 19:21:13 -0700 In-Reply-To: <20230517022115.3033604-1-pcc@google.com> Message-Id: <20230517022115.3033604-4-pcc@google.com> Mime-Version: 1.0 References: <20230517022115.3033604-1-pcc@google.com> X-Mailer: git-send-email 2.40.1.606.ga4b1b128d6-goog Subject: [PATCH v3 3/3] arm64: mte: Simplify swap tag restoration logic From: Peter Collingbourne To: Catalin Marinas Cc: Peter Collingbourne , "=?UTF-8?q?Qun-wei=20Lin=20=28=E6=9E=97=E7=BE=A4=E5=B4=B4=29?=" , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, "surenb@google.com" , "david@redhat.com" , "=?UTF-8?q?Chinwen=20Chang=20=28=E5=BC=B5=E9=8C=A6=E6=96=87=29?=" , "kasan-dev@googlegroups.com" , "=?UTF-8?q?Kuan-Ying=20Lee=20=28=E6=9D=8E=E5=86=A0=E7=A9=8E=29?=" , "=?UTF-8?q?Casper=20Li=20=28=E6=9D=8E=E4=B8=AD=E6=A6=AE=29?=" , "gregkh@linuxfoundation.org" , vincenzo.frascino@arm.com, Alexandru Elisei , will@kernel.org, eugenis@google.com, Steven Price Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Stat-Signature: 8m68ykbz1jckw6e877hrf9tkckahzoea X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: D04772000A X-HE-Tag: 1684290090-690556 X-HE-Meta: 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 WVGV2jas 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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. Because we can now rely on the page being locked, we no longer need to handle the case where a page is having its tags restored by multiple tasks concurrently, so we can slightly simplify the logic in mte_restore_tags(). Signed-off-by: Peter Collingbourne Link: https://linux-review.googlesource.com/id/I8ad54476f3b2d0144ccd8ce0c1d7a2963e5ff6f3 --- 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 ++++++-------------------------- arch/arm64/mm/mteswap.c | 7 +++--- 4 files changed, 14 insertions(+), 48 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(); diff --git a/arch/arm64/mm/mteswap.c b/arch/arm64/mm/mteswap.c index cd508ba80ab1..3a78bf1b1364 100644 --- a/arch/arm64/mm/mteswap.c +++ b/arch/arm64/mm/mteswap.c @@ -53,10 +53,9 @@ void mte_restore_tags(swp_entry_t entry, struct page *page) if (!tags) return; - if (try_page_mte_tagging(page)) { - mte_restore_page_tags(page_address(page), tags); - set_page_mte_tagged(page); - } + WARN_ON_ONCE(!try_page_mte_tagging(page)); + mte_restore_page_tags(page_address(page), tags); + set_page_mte_tagged(page); } void mte_invalidate_tags(int type, pgoff_t offset) -- 2.40.1.606.ga4b1b128d6-goog