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Sun, 04 Oct 2026 03:03:24 +0000 X-Mizu-Trace-ID: f5c2ae1123ce7d6d X-Migadu-Flow: FLOW_OUT From: Lance Yang To: pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu Cc: alex@ghiti.fr, akpm@linux-foundation.org, zhangchunyan@iscas.ac.cn, rppt@kernel.org, kas@kernel.org, david@kernel.org, andrew+kernel@donnellan.id.au, rmclure@linux.ibm.com, debug@rivosinc.com, baolin.wang@linux.alibaba.com, usama.arif@linux.dev, wangruikang@iscas.ac.cn, namcao@linutronix.de, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, alexghiti@rivosinc.com, viro@zeniv.linux.org.uk, ajones@ventanamicro.com, arnd@arndb.de, axelrasmussen@google.com, brauner@kernel.org, conor.dooley@microchip.com, conor@kernel.org, jack@suse.cz, liam@infradead.org, ljs@kernel.org, mhocko@suse.com, paul.walmsley@sifive.com, peterx@redhat.com, robh@kernel.org, surenb@google.com, vbabka@kernel.org, yuanchu@google.com, stable@vger.kernel.org, pasha.tatashin@soleen.com, linux-mm@kvack.org, me@ziyao.cc, Lance Yang Subject: [PATCH 1/1] riscv/mm: fix soft-dirty migration PMDs being treated as present Date: Sun, 4 Oct 2026 11:03:12 +0800 Message-ID: <20261004030312.90163-1-lance.yang@linux.dev> X-Mailer: git-send-email 2.49.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: B393820006 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: 5rbkdp9y686fczy5m6asjow8kfg9gprm X-HE-Tag: 1791083006-772485 X-HE-Meta: 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 yhmP+TXj ZwaL9cQZfsrVwF0oW2TBXpKSy6z9R5aygN5C++LrxuUDYkAuc37YP05OX6B5gApqAOmdQRcaNHLaOEwdxeu9jNKOieEbYOBblDF0BvZPBR4tZcCgWc0PlB7SKR8ngAG9ouOnQ8eBDZxVbVfm9rBcsBejZDZ6fZvhchBOMGJzRP2z1UpVnUqkMenHoUGHWIQYnqyxj+H/XHiQuDJo95uUmv2kJBTiSoCVca1AoUHLseZOHbh294Lf0xh8xwTKMxkXwsxBRVtLWUBabE8Z9XDVp918kPTodHxosR7Siev4ZsC890LLuhF+1AkY1uIyTFDIWrtu4H5fCTPgoWApXY8JXlHbTRw7LkumLNnh6rUT5/C0q/B4= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: RISC-V uses _PAGE_EXEC for swap soft-dirty tracking when CONFIG_MEM_SOFT_DIRTY is enabled and Svrsw60t59b is available. That's a problem for PMD migration entries, since pmd_present() also checks _PAGE_LEAF (R/W/X) to recognize THPs with _PAGE_PRESENT temporarily cleared during splitting. When a soft-dirty THP is migrated, set_pmd_migration_entry() preserves soft-dirty with pmd_swp_mksoft_dirty(), setting the X bit in the migration PMD. Even with _PAGE_PRESENT clear, we end up treating a migration PMD as a present THP! The fault handler skips pmd_migration_entry_wait(), and a write fault can end up in do_huge_pmd_wp_page(), where pmd_page() decodes the migration entry as a mapped PFN. Move the swap soft-dirty bit to bit 12 and start the swap offset at bit 13 when CONFIG_MEM_SOFT_DIRTY is enabled. This keeps R/W/X clear in migration PMDs and lets us keep the existing pmd_present() check for invalidated THPs. Leave the offset at bit 12 when soft-dirty tracking is disabled. Fixes: 2a3ebad4db63 ("riscv: mm: add soft-dirty page tracking support") Cc: stable@vger.kernel.org Signed-off-by: Lance Yang --- I found this while reviewing Usama's PMD-level swap entries series [1] and comparing the swap flag bits with the PMD presence checks across architectures. [1] https://lore.kernel.org/all/20261002095503.3585565-1-usama.arif@linux.dev/ arch/riscv/include/asm/pgtable-bits.h | 6 +++--- arch/riscv/include/asm/pgtable.h | 10 ++++++---- 2 files changed, 9 insertions(+), 7 deletions(-) diff --git a/arch/riscv/include/asm/pgtable-bits.h b/arch/riscv/include/asm/pgtable-bits.h index d5a86b4df3ce6..d84b459e010c1 100644 --- a/arch/riscv/include/asm/pgtable-bits.h +++ b/arch/riscv/include/asm/pgtable-bits.h @@ -27,12 +27,12 @@ ((riscv_has_extension_unlikely(RISCV_ISA_EXT_SVRSW60T59B)) ? \ (1UL << 59) : 0) /* - * Bit 3 is always zero for swap entry computation, so we - * can borrow it for swap page soft-dirty tracking. + * Bit 12 is reserved for swap soft-dirty tracking. The swap offset + * starts at bit 13 when CONFIG_MEM_SOFT_DIRTY is enabled. */ #define _PAGE_SWP_SOFT_DIRTY \ ((riscv_has_extension_unlikely(RISCV_ISA_EXT_SVRSW60T59B)) ? \ - _PAGE_EXEC : 0) + (1UL << 12) : 0) #else #define _PAGE_SOFT_DIRTY 0 #define _PAGE_SWP_SOFT_DIRTY 0 diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h index b644db16bda94..acaf6d3b54d04 100644 --- a/arch/riscv/include/asm/pgtable.h +++ b/arch/riscv/include/asm/pgtable.h @@ -1178,18 +1178,20 @@ static inline pud_t pud_modify(pud_t pud, pgprot_t newprot) * * Format of swap PTE: * bit 0: _PAGE_PRESENT (zero) - * bit 1 to 2: (zero) - * bit 3: _PAGE_SWP_SOFT_DIRTY + * bit 1 to 3: _PAGE_LEAF (zero) * bit 4: _PAGE_SWP_UFFD * bit 5: _PAGE_PROT_NONE (zero) * bit 6: exclusive marker * bits 7 to 11: swap type - * bits 12 to XLEN-1: swap offset + * bit 12: _PAGE_SWP_SOFT_DIRTY (CONFIG_MEM_SOFT_DIRTY) + * bits 12/13 to XLEN-1: swap offset (without/with CONFIG_MEM_SOFT_DIRTY) */ #define __SWP_TYPE_SHIFT 7 #define __SWP_TYPE_BITS 5 #define __SWP_TYPE_MASK ((1UL << __SWP_TYPE_BITS) - 1) -#define __SWP_OFFSET_SHIFT (__SWP_TYPE_BITS + __SWP_TYPE_SHIFT) +#define __SWP_OFFSET_SHIFT \ + (__SWP_TYPE_BITS + __SWP_TYPE_SHIFT + \ + IS_ENABLED(CONFIG_MEM_SOFT_DIRTY)) #define MAX_SWAPFILES_CHECK() \ BUILD_BUG_ON(MAX_SWAPFILES_SHIFT > __SWP_TYPE_BITS) -- 2.49.0