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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, qi.zheng@linux.dev, luizcap@redhat.com, kernel-team@meta.com, Usama Arif , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org Subject: [PATCH v9 07/32] x86: mm: add PMD swap-exclusive helpers Date: Thu, 5 Nov 2026 10:38:51 -0800 Message-ID: <20261105183940.2236717-8-usama.arif@linux.dev> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261105183940.2236717-1-usama.arif@linux.dev> References: <20261105183940.2236717-1-usama.arif@linux.dev> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Prepare for keeping a PMD-mapped anonymous THP mapped by a PMD across the swap round-trip, which makes PG_anon_exclusive have to survive in a swap PMD and not just in a swap PTE. x86-64 encodes a swap PMD exactly like a swap PTE, so the new helpers reuse _PAGE_SWP_EXCLUSIVE, bit 3, which the swap-entry layout already reserves for PG_anon_exclusive. 32-bit x86 aliases that bit to _PAGE_PSE and does not select ARCH_HAS_PMD_SOFTLEAVES; assert that, because an exclusive swap PMD would otherwise be pmd_present(). Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: Dave Hansen Cc: x86@kernel.org Signed-off-by: Usama Arif Reviewed-by: Kiryl Shutsemau (Meta) Reviewed-by: David Hildenbrand (Arm) Reviewed-by: Zi Yan --- arch/x86/include/asm/pgtable.h | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h index 000fc6c1ca37c..22cf9b57a135b 100644 --- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -1529,6 +1529,29 @@ 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 +/* + * _PAGE_SWP_EXCLUSIVE must not alias _PAGE_PSE, which would make an + * exclusive swap PMD present. + */ +static_assert(_PAGE_SWP_EXCLUSIVE != _PAGE_PSE); + +static inline pmd_t pmd_swp_mkexclusive(pmd_t pmd) +{ + return pmd_set_flags(pmd, _PAGE_SWP_EXCLUSIVE); +} + +static inline bool 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) { -- 2.53.0-Meta