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s=arc-20220608; d=hostedemail.com; t=1711474678; a=rsa-sha256; cv=none; b=oIzaqjJyjF9t2wunCCeFUYAG+lN2+j4qs9IJQbHRQMrA7S+OflJ+3nsVyfxvxBF43MqpX+ EWCkaZHJJh6dnJKD3mYZxLvvyDmqQvH7q5hmVlSKaWxtmVmI7awGbWA0fXqcenH5UeSFAA BQMqqYdnos5bh5nZRBzq0KIigQhllFM= ARC-Authentication-Results: i=1; imf10.hostedemail.com; dkim=none; spf=pass (imf10.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com; dmarc=pass (policy=none) header.from=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id B9AE32F4; Tue, 26 Mar 2024 10:38:30 -0700 (PDT) Received: from [10.1.29.179] (XHFQ2J9959.cambridge.arm.com [10.1.29.179]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 21A103F64C; Tue, 26 Mar 2024 10:37:53 -0700 (PDT) Message-ID: <03a23867-3982-4d24-896c-cf55f4d94b43@arm.com> Date: Tue, 26 Mar 2024 17:37:52 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/1] arm64: mm: swap: support THP_SWAP on hardware with MTE Content-Language: en-GB To: Barry Song <21cnbao@gmail.com>, catalin.marinas@arm.com, will@kernel.org, akpm@linux-foundation.org, hughd@google.com, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org Cc: chrisl@kernel.org, mark.rutland@arm.com, steven.price@arm.com, david@redhat.com, willy@infradead.org, Barry Song , Kemeng Shi , Anshuman Khandual , Peter Collingbourne , Yosry Ahmed , Peter Xu , Lorenzo Stoakes , "Mike Rapoport (IBM)" , "Aneesh Kumar K.V" , Rick Edgecombe References: <20240322114136.61386-1-21cnbao@gmail.com> <20240322114136.61386-2-21cnbao@gmail.com> From: Ryan Roberts In-Reply-To: <20240322114136.61386-2-21cnbao@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: 1wfugon64g4ujub9a5f6ejc8pmnoxxxe X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: E4593C0002 X-Rspam-User: X-HE-Tag: 1711474677-108743 X-HE-Meta: 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 SW0mSDlV 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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: List-Subscribe: List-Unsubscribe: On 22/03/2024 11:41, Barry Song wrote: > From: Barry Song > > Commit d0637c505f8a1 ("arm64: enable THP_SWAP for arm64") brings up > THP_SWAP on ARM64, but it doesn't enable THP_SWP on hardware with > MTE as the MTE code works with the assumption tags save/restore is > always handling a folio with only one page. > > The limitation should be removed as more and more ARM64 SoCs have > this feature. Co-existence of MTE and THP_SWAP becomes more and > more important. > > This patch makes MTE tags saving support large folios, then we don't > need to split large folios into base pages for swapping out on ARM64 > SoCs with MTE any more. > > arch_prepare_to_swap() should take folio rather than page as parameter > because we support THP swap-out as a whole. It saves tags for all > pages in a large folio. > > As now we are restoring tags based-on folio, in arch_swap_restore(), > we may increase some extra loops and early-exitings while refaulting > a large folio which is still in swapcache in do_swap_page(). In case > a large folio has nr pages, do_swap_page() will only set the PTE of > the particular page which is causing the page fault. > Thus do_swap_page() runs nr times, and each time, arch_swap_restore() > will loop nr times for those subpages in the folio. So right now the > algorithmic complexity becomes O(nr^2). > > Once we support mapping large folios in do_swap_page(), extra loops > and early-exitings will decrease while not being completely removed > as a large folio might get partially tagged in corner cases such as, > 1. a large folio in swapcache can be partially unmapped, thus, MTE > tags for the unmapped pages will be invalidated; > 2. users might use mprotect() to set MTEs on a part of a large folio. > > arch_thp_swp_supported() is dropped since ARM64 MTE was the only one > who needed it. > > Cc: Catalin Marinas > Cc: Will Deacon > Cc: Ryan Roberts > Cc: Mark Rutland > Cc: David Hildenbrand > Cc: Kemeng Shi > Cc: "Matthew Wilcox (Oracle)" > Cc: Anshuman Khandual > Cc: Peter Collingbourne > Cc: Steven Price > Cc: Yosry Ahmed > Cc: Peter Xu > Cc: Lorenzo Stoakes > Cc: "Mike Rapoport (IBM)" > Cc: Hugh Dickins > CC: "Aneesh Kumar K.V" > Cc: Rick Edgecombe > Signed-off-by: Barry Song > Reviewed-by: Steven Price > Acked-by: Chris Li Reviewed-by: Ryan Roberts It would be really great if we can get this in for v6.10! > --- > arch/arm64/include/asm/pgtable.h | 19 ++------------ > arch/arm64/mm/mteswap.c | 45 ++++++++++++++++++++++++++++++++ > include/linux/huge_mm.h | 12 --------- > include/linux/pgtable.h | 2 +- > mm/internal.h | 14 ++++++++++ > mm/memory.c | 2 +- > mm/page_io.c | 2 +- > mm/shmem.c | 2 +- > mm/swap_slots.c | 2 +- > mm/swapfile.c | 2 +- > 10 files changed, 67 insertions(+), 35 deletions(-) > > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h > index afdd56d26ad7..259325e6b7e8 100644 > --- a/arch/arm64/include/asm/pgtable.h > +++ b/arch/arm64/include/asm/pgtable.h > @@ -49,12 +49,6 @@ > __flush_tlb_range(vma, addr, end, PUD_SIZE, false, 1) > #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ > > -static inline bool arch_thp_swp_supported(void) > -{ > - return !system_supports_mte(); > -} > -#define arch_thp_swp_supported arch_thp_swp_supported > - > /* > * Outside of a few very special situations (e.g. hibernation), we always > * use broadcast TLB invalidation instructions, therefore a spurious page > @@ -1280,12 +1274,7 @@ static inline pmd_t pmdp_establish(struct vm_area_struct *vma, > #ifdef CONFIG_ARM64_MTE > > #define __HAVE_ARCH_PREPARE_TO_SWAP > -static inline int arch_prepare_to_swap(struct page *page) > -{ > - if (system_supports_mte()) > - return mte_save_tags(page); > - return 0; > -} > +extern int arch_prepare_to_swap(struct folio *folio); > > #define __HAVE_ARCH_SWAP_INVALIDATE > static inline void arch_swap_invalidate_page(int type, pgoff_t offset) > @@ -1301,11 +1290,7 @@ 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); > -} > +extern void arch_swap_restore(swp_entry_t entry, struct folio *folio); > > #endif /* CONFIG_ARM64_MTE */ > > diff --git a/arch/arm64/mm/mteswap.c b/arch/arm64/mm/mteswap.c > index a31833e3ddc5..63e8d72f202a 100644 > --- a/arch/arm64/mm/mteswap.c > +++ b/arch/arm64/mm/mteswap.c > @@ -68,6 +68,13 @@ void mte_invalidate_tags(int type, pgoff_t offset) > mte_free_tag_storage(tags); > } > > +static inline void __mte_invalidate_tags(struct page *page) > +{ > + swp_entry_t entry = page_swap_entry(page); > + > + mte_invalidate_tags(swp_type(entry), swp_offset(entry)); > +} > + > void mte_invalidate_tags_area(int type) > { > swp_entry_t entry = swp_entry(type, 0); > @@ -83,3 +90,41 @@ void mte_invalidate_tags_area(int type) > } > xa_unlock(&mte_pages); > } > + > +int arch_prepare_to_swap(struct folio *folio) > +{ > + long i, nr; > + int err; > + > + if (!system_supports_mte()) > + return 0; > + > + nr = folio_nr_pages(folio); > + > + for (i = 0; i < nr; i++) { > + err = mte_save_tags(folio_page(folio, i)); > + if (err) > + goto out; > + } > + return 0; > + > +out: > + while (i--) > + __mte_invalidate_tags(folio_page(folio, i)); > + return err; > +} > + > +void arch_swap_restore(swp_entry_t entry, struct folio *folio) > +{ > + long i, nr; > + > + if (!system_supports_mte()) > + return; > + > + nr = folio_nr_pages(folio); > + > + for (i = 0; i < nr; i++) { > + mte_restore_tags(entry, folio_page(folio, i)); > + entry.val++; > + } > +} > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h > index de0c89105076..e04b93c43965 100644 > --- a/include/linux/huge_mm.h > +++ b/include/linux/huge_mm.h > @@ -535,16 +535,4 @@ static inline int split_folio_to_order(struct folio *folio, int new_order) > #define split_folio_to_list(f, l) split_folio_to_list_to_order(f, l, 0) > #define split_folio(f) split_folio_to_order(f, 0) > > -/* > - * archs that select ARCH_WANTS_THP_SWAP but don't support THP_SWP due to > - * limitations in the implementation like arm64 MTE can override this to > - * false > - */ > -#ifndef arch_thp_swp_supported > -static inline bool arch_thp_swp_supported(void) > -{ > - return true; > -} > -#endif > - > #endif /* _LINUX_HUGE_MM_H */ > diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h > index 85fc7554cd52..b10a7dd615bd 100644 > --- a/include/linux/pgtable.h > +++ b/include/linux/pgtable.h > @@ -1052,7 +1052,7 @@ static inline int arch_unmap_one(struct mm_struct *mm, > * prototypes must be defined in the arch-specific asm/pgtable.h file. > */ > #ifndef __HAVE_ARCH_PREPARE_TO_SWAP > -static inline int arch_prepare_to_swap(struct page *page) > +static inline int arch_prepare_to_swap(struct folio *folio) > { > return 0; > } > diff --git a/mm/internal.h b/mm/internal.h > index 7e486f2c502c..2551e93dd885 100644 > --- a/mm/internal.h > +++ b/mm/internal.h > @@ -76,6 +76,20 @@ static inline int folio_nr_pages_mapped(struct folio *folio) > return atomic_read(&folio->_nr_pages_mapped) & FOLIO_PAGES_MAPPED; > } > > +/* > + * Retrieve the first entry of a folio based on a provided entry within the > + * folio. We cannot rely on folio->swap as there is no guarantee that it has > + * been initialized. Used for calling arch_swap_restore() > + */ > +static inline swp_entry_t folio_swap(swp_entry_t entry, struct folio *folio) > +{ > + swp_entry_t swap = { > + .val = ALIGN_DOWN(entry.val, folio_nr_pages(folio)), > + }; > + > + return swap; > +} > + > static inline void *folio_raw_mapping(struct folio *folio) > { > unsigned long mapping = (unsigned long)folio->mapping; > diff --git a/mm/memory.c b/mm/memory.c > index f2bc6dd15eb8..b7cab8be8632 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -4188,7 +4188,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) > * when reading from swap. This metadata may be indexed by swap entry > * so this must be called before swap_free(). > */ > - arch_swap_restore(entry, folio); > + arch_swap_restore(folio_swap(entry, folio), folio); > > /* > * Remove the swap entry and conditionally try to free up the swapcache. > diff --git a/mm/page_io.c b/mm/page_io.c > index ae2b49055e43..a9a7c236aecc 100644 > --- a/mm/page_io.c > +++ b/mm/page_io.c > @@ -189,7 +189,7 @@ int swap_writepage(struct page *page, struct writeback_control *wbc) > * Arch code may have to preserve more data than just the page > * contents, e.g. memory tags. > */ > - ret = arch_prepare_to_swap(&folio->page); > + ret = arch_prepare_to_swap(folio); > if (ret) { > folio_mark_dirty(folio); > folio_unlock(folio); > diff --git a/mm/shmem.c b/mm/shmem.c > index 0aad0d9a621b..44c1519ba881 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -1913,7 +1913,7 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index, > * Some architectures may have to restore extra metadata to the > * folio after reading from swap. > */ > - arch_swap_restore(swap, folio); > + arch_swap_restore(folio_swap(swap, folio), folio); > > if (shmem_should_replace_folio(folio, gfp)) { > error = shmem_replace_folio(&folio, gfp, info, index); > diff --git a/mm/swap_slots.c b/mm/swap_slots.c > index 90973ce7881d..53abeaf1371d 100644 > --- a/mm/swap_slots.c > +++ b/mm/swap_slots.c > @@ -310,7 +310,7 @@ swp_entry_t folio_alloc_swap(struct folio *folio) > entry.val = 0; > > if (folio_test_large(folio)) { > - if (IS_ENABLED(CONFIG_THP_SWAP) && arch_thp_swp_supported()) > + if (IS_ENABLED(CONFIG_THP_SWAP)) > get_swap_pages(1, &entry, folio_nr_pages(folio)); > goto out; > } > diff --git a/mm/swapfile.c b/mm/swapfile.c > index 4919423cce76..5e6d2304a2a4 100644 > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -1806,7 +1806,7 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd, > * when reading from swap. This metadata may be indexed by swap entry > * so this must be called before swap_free(). > */ > - arch_swap_restore(entry, folio); > + arch_swap_restore(folio_swap(entry, folio), folio); > > dec_mm_counter(vma->vm_mm, MM_SWAPENTS); > inc_mm_counter(vma->vm_mm, MM_ANONPAGES);