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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1783949786; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=tUgA6wQcfP1IvEKm+e/GRsSnX/F4Dv4Bzc78RNPqdmU=; b=DcwT1fZPpMKPqiLd5rSn8mnpKpGJ9Q6JT2j5O2Si+GNVm15oKn+Ol6/Fqs53X6xaAxMTcd ZiaHo5TljcU9gFYCulrB3Z69li5qiG1V5H4tWL99qUXrJG/ZFwedC14AeWvYWEfjW4ZU95 bwhL3R2IXTyWdXuq71Y0V2Sv+gipddE= From: Usama Arif To: Andrew Morton , david@kernel.org, chrisl@kernel.org, kasong@tencent.com, ljs@kernel.org, ziy@nvidia.com, linux-mm@kvack.org Cc: ying.huang@linux.alibaba.com, Baoquan He , willy@infradead.org, youngjun.park@lge.com, hannes@cmpxchg.org, riel@surriel.com, shakeel.butt@linux.dev, alex@ghiti.fr, kas@kernel.org, baohua@kernel.org, dev.jain@arm.com, baolin.wang@linux.alibaba.com, npache@redhat.com, Liam R. Howlett , ryan.roberts@arm.com, Vlastimil Babka , lance.yang@linux.dev, linux-kernel@vger.kernel.org, nphamcs@gmail.com, shikemeng@huaweicloud.com, yosry@kernel.org, kernel-team@meta.com, Usama Arif Subject: [PATCH v4 01/11] mm: add PMD swap entry detection support Date: Mon, 13 Jul 2026 06:35:36 -0700 Message-ID: <20260713133613.2707815-2-usama.arif@linux.dev> In-Reply-To: <20260713133613.2707815-1-usama.arif@linux.dev> References: <20260713133613.2707815-1-usama.arif@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT Currently when a PMD-mapped THP is swapped out, the PMD is always split into 512 PTE-level swap entries. To preserve huge page information across swap cycles, later patches will install a single PMD-level swap entry instead. This patch adds the infrastructure to detect those entries. Teach the softleaf layer to recognise PMD swap entries: pmd_is_swap_entry() detects them and softleaf_is_valid_pmd_entry() accepts them as a valid non-present type. Clear the exclusive overlay bit in softleaf_from_pmd() before decoding, matching how soft_dirty and uffd_wp bits are already stripped. Add pmd_swp_mkexclusive(), pmd_swp_exclusive(), and pmd_swp_clear_exclusive() helpers to each architecture that supports PMD softleaf entries (x86, arm64, s390, riscv, loongarch, powerpc), mirroring the existing PTE swap exclusive helpers in each arch's pgtable.h. Provide generic no-op PMD swap exclusive fallbacks for architectures without PMD softleaf support, matching the generic PMD swap soft-dirty fallbacks. Signed-off-by: Usama Arif --- arch/arm64/include/asm/pgtable.h | 6 +++++ arch/loongarch/include/asm/pgtable.h | 19 ++++++++++++++++ arch/powerpc/include/asm/book3s/64/pgtable.h | 17 ++++++++++++++ arch/riscv/include/asm/pgtable.h | 17 ++++++++++++++ arch/s390/include/asm/pgtable.h | 17 ++++++++++++++ arch/x86/include/asm/pgtable.h | 17 ++++++++++++++ include/linux/leafops.h | 24 ++++++++++++++++---- include/linux/pgtable.h | 17 ++++++++++++++ 8 files changed, 129 insertions(+), 5 deletions(-) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index a2681d755358..860f95573d1f 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -598,6 +598,12 @@ static inline int pmd_protnone(pmd_t pmd) #define pmd_swp_clear_uffd(pmd) \ pte_pmd(pte_swp_clear_uffd(pmd_pte(pmd))) #endif /* CONFIG_HAVE_ARCH_USERFAULTFD_WP */ +#ifdef CONFIG_ARCH_HAS_PMD_SOFTLEAVES +#define pmd_swp_exclusive(pmd) pte_swp_exclusive(pmd_pte(pmd)) +#define pmd_swp_mkexclusive(pmd) pte_pmd(pte_swp_mkexclusive(pmd_pte(pmd))) +#define pmd_swp_clear_exclusive(pmd) \ + pte_pmd(pte_swp_clear_exclusive(pmd_pte(pmd))) +#endif #define pmd_write(pmd) pte_write(pmd_pte(pmd)) diff --git a/arch/loongarch/include/asm/pgtable.h b/arch/loongarch/include/asm/pgtable.h index 1952e34bc8ee..aa8e1223d397 100644 --- a/arch/loongarch/include/asm/pgtable.h +++ b/arch/loongarch/include/asm/pgtable.h @@ -357,6 +357,25 @@ static inline pte_t pte_swp_clear_exclusive(pte_t pte) return pte; } +#ifdef CONFIG_ARCH_HAS_PMD_SOFTLEAVES +static inline pmd_t pmd_swp_mkexclusive(pmd_t pmd) +{ + pmd_val(pmd) |= _PAGE_SWP_EXCLUSIVE; + return pmd; +} + +static inline bool pmd_swp_exclusive(pmd_t pmd) +{ + return pmd_val(pmd) & _PAGE_SWP_EXCLUSIVE; +} + +static inline pmd_t pmd_swp_clear_exclusive(pmd_t pmd) +{ + pmd_val(pmd) &= ~_PAGE_SWP_EXCLUSIVE; + return pmd; +} +#endif + #define pte_none(pte) (!(pte_val(pte) & ~_PAGE_GLOBAL)) #define pte_present(pte) (pte_val(pte) & (_PAGE_PRESENT | _PAGE_PROTNONE)) #define pte_no_exec(pte) (pte_val(pte) & _PAGE_NO_EXEC) diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h index f4db7d7fbd5c..6a899d0793b3 100644 --- a/arch/powerpc/include/asm/book3s/64/pgtable.h +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h @@ -699,6 +699,23 @@ static inline pte_t pte_swp_clear_exclusive(pte_t pte) return __pte_raw(pte_raw(pte) & cpu_to_be64(~_PAGE_SWP_EXCLUSIVE)); } +#ifdef CONFIG_ARCH_HAS_PMD_SOFTLEAVES +static inline pmd_t pmd_swp_mkexclusive(pmd_t pmd) +{ + return __pmd_raw(pmd_raw(pmd) | cpu_to_be64(_PAGE_SWP_EXCLUSIVE)); +} + +static inline bool pmd_swp_exclusive(pmd_t pmd) +{ + return !!(pmd_raw(pmd) & cpu_to_be64(_PAGE_SWP_EXCLUSIVE)); +} + +static inline pmd_t pmd_swp_clear_exclusive(pmd_t pmd) +{ + return __pmd_raw(pmd_raw(pmd) & cpu_to_be64(~_PAGE_SWP_EXCLUSIVE)); +} +#endif + static inline bool check_pte_access(unsigned long access, unsigned long ptev) { /* diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h index 7f21742b2b6a..558bb99cdaca 100644 --- a/arch/riscv/include/asm/pgtable.h +++ b/arch/riscv/include/asm/pgtable.h @@ -927,6 +927,23 @@ static inline pmd_t pmd_swp_clear_uffd(pmd_t pmd) } #endif /* CONFIG_HAVE_ARCH_USERFAULTFD_WP */ +#ifdef CONFIG_ARCH_HAS_PMD_SOFTLEAVES +static inline bool pmd_swp_exclusive(pmd_t pmd) +{ + return pte_swp_exclusive(pmd_pte(pmd)); +} + +static inline pmd_t pmd_swp_mkexclusive(pmd_t pmd) +{ + return pte_pmd(pte_swp_mkexclusive(pmd_pte(pmd))); +} + +static inline pmd_t pmd_swp_clear_exclusive(pmd_t pmd) +{ + return pte_pmd(pte_swp_clear_exclusive(pmd_pte(pmd))); +} +#endif + #ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY static inline bool pmd_soft_dirty(pmd_t pmd) { diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h index e882663a58e7..490e4a3464b1 100644 --- a/arch/s390/include/asm/pgtable.h +++ b/arch/s390/include/asm/pgtable.h @@ -870,6 +870,23 @@ static inline pte_t pte_swp_clear_exclusive(pte_t pte) return clear_pte_bit(pte, __pgprot(_PAGE_SWP_EXCLUSIVE)); } +#ifdef CONFIG_ARCH_HAS_PMD_SOFTLEAVES +static inline pmd_t pmd_swp_mkexclusive(pmd_t pmd) +{ + return set_pmd_bit(pmd, __pgprot(_PAGE_SWP_EXCLUSIVE)); +} + +static inline bool pmd_swp_exclusive(pmd_t pmd) +{ + return pmd_val(pmd) & _PAGE_SWP_EXCLUSIVE; +} + +static inline pmd_t pmd_swp_clear_exclusive(pmd_t pmd) +{ + return clear_pmd_bit(pmd, __pgprot(_PAGE_SWP_EXCLUSIVE)); +} +#endif + static inline int pte_soft_dirty(pte_t pte) { return pte_val(pte) & _PAGE_SOFT_DIRTY; diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h index 8e0018fadd14..b5da5447e83d 100644 --- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -1525,6 +1525,23 @@ static inline pte_t pte_swp_clear_exclusive(pte_t pte) return pte_clear_flags(pte, _PAGE_SWP_EXCLUSIVE); } +#ifdef CONFIG_ARCH_HAS_PMD_SOFTLEAVES +static inline pmd_t pmd_swp_mkexclusive(pmd_t pmd) +{ + return pmd_set_flags(pmd, _PAGE_SWP_EXCLUSIVE); +} + +static inline int pmd_swp_exclusive(pmd_t pmd) +{ + return pmd_flags(pmd) & _PAGE_SWP_EXCLUSIVE; +} + +static inline pmd_t pmd_swp_clear_exclusive(pmd_t pmd) +{ + return pmd_clear_flags(pmd, _PAGE_SWP_EXCLUSIVE); +} +#endif + #ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY static inline pte_t pte_swp_mksoft_dirty(pte_t pte) { diff --git a/include/linux/leafops.h b/include/linux/leafops.h index 4c1476ae3234..2beee484a87d 100644 --- a/include/linux/leafops.h +++ b/include/linux/leafops.h @@ -102,6 +102,8 @@ static inline softleaf_t softleaf_from_pmd(pmd_t pmd) pmd = pmd_swp_clear_soft_dirty(pmd); if (pmd_swp_uffd(pmd)) pmd = pmd_swp_clear_uffd(pmd); + if (pmd_swp_exclusive(pmd)) + pmd = pmd_swp_clear_exclusive(pmd); arch_entry = __pmd_to_swp_entry(pmd); /* Temporary until swp_entry_t eliminated. */ @@ -634,18 +636,30 @@ static inline bool pmd_is_migration_entry(pmd_t pmd) */ static inline bool softleaf_is_valid_pmd_entry(softleaf_t entry) { - /* Only device private, migration entries valid for PMD. */ + /* Device private, migration, and swap entries valid for PMD. */ return softleaf_is_device_private(entry) || - softleaf_is_migration(entry); + softleaf_is_migration(entry) || + softleaf_is_swap(entry); +} + +/** + * pmd_is_swap_entry() - Does this PMD entry encode an actual swap entry? + * @pmd: PMD entry. + * + * Returns: true if the PMD encodes a swap entry, otherwise false. + */ +static inline bool pmd_is_swap_entry(pmd_t pmd) +{ + return softleaf_is_swap(softleaf_from_pmd(pmd)); } /** * pmd_is_valid_softleaf() - Is this PMD entry a valid softleaf entry? * @pmd: PMD entry. * - * PMD leaf entries are valid only if they are device private or migration - * entries. This function asserts that a PMD leaf entry is valid in this - * respect. + * PMD leaf entries are valid only if they are device private, migration, + * or swap entries. This function asserts that a PMD leaf entry is valid + * in this respect. * * Returns: true if the PMD entry is a valid leaf entry, otherwise false. */ diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h index 8c093c119e5a..e10a7e91e426 100644 --- a/include/linux/pgtable.h +++ b/include/linux/pgtable.h @@ -1917,6 +1917,23 @@ static inline pmd_t pmd_swp_clear_soft_dirty(pmd_t pmd) } #endif +#ifndef CONFIG_ARCH_HAS_PMD_SOFTLEAVES +static inline pmd_t pmd_swp_mkexclusive(pmd_t pmd) +{ + return pmd; +} + +static inline bool pmd_swp_exclusive(pmd_t pmd) +{ + return false; +} + +static inline pmd_t pmd_swp_clear_exclusive(pmd_t pmd) +{ + return pmd; +} +#endif + #ifndef __HAVE_PFNMAP_TRACKING /* * Interfaces that can be used by architecture code to keep track of -- 2.53.0-Meta