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Wed, 16 Sep 2026 10:31:55 -0400 (EDT) Date: Wed, 16 Sep 2026 15:31:54 +0100 From: Kiryl Shutsemau To: Usama Arif Cc: Andrew Morton , david@kernel.org, chrisl@kernel.org, kasong@tencent.com, ljs@kernel.org, ziy@nvidia.com, linux-mm@kvack.org, 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, baohua@kernel.org, dev.jain@arm.com, baolin.wang@linux.alibaba.com, Nico Pache , "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, qi.zheng@linux.dev, luizcap@redhat.com, kernel-team@meta.com, Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org Subject: Re: [RESEND v7 07/29] x86: mm: add PMD swap-exclusive helpers Message-ID: References: <20260914122950.3283997-1-usama.arif@linux.dev> <20260914122950.3283997-8-usama.arif@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260914122950.3283997-8-usama.arif@linux.dev> X-Rspam-User: X-Rspamd-Queue-Id: 426A2C000E X-Stat-Signature: 4fdf8th3ewszgyycgrypic4krgit8fbi X-Rspamd-Server: rspam01 X-HE-Tag: 1789569127-110881 X-HE-Meta: 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 tXc+pZsE pcTLrnWXEqgEiFZtx3L65L9AeVsFQh6+htkAn1H4H/hzpJSbmXqHV3TKegB0AYRYh6F+eDPAo2Dh12G0krvSgVwy6CI/UaOqq3x/WbkD/yH3EFNUftlGIVWhPUtZhx+o+8o+FrRwpLpRkQ/jnHG7kxH2u+vrZvFY/kcatNxgX8Pf0Uvt/SN1iALIIjcZNJktwZrFXSO0JSV+mRvsOUq51oFdyh8aqhvDFth+6Y5SXsZS5y4HsG25+hc6YMCMqvdeRmHlytT42UDSQNAtcXYmxWVSLGwtEXWmHbdGQq4oZ1eW/ZFWAod4C8mQubJsWtufurLPXRmAdy31VuZ81TaKGn1YQfmPopwRK43VU Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Sep 14, 2026 at 05:27:57AM -0700, Usama Arif wrote: > A later patch keeps a PMD-mapped anonymous THP mapped by a PMD across the > swap round-trip, so PG_anon_exclusive now has 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. > > Cc: Thomas Gleixner > Cc: Ingo Molnar > Cc: Borislav Petkov > Cc: Dave Hansen > Cc: x86@kernel.org > Signed-off-by: Usama Arif > --- > arch/x86/include/asm/pgtable.h | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > > diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h > index d551120a7c889..a2d1cd03cba23 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 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 > + I was about to comment that it is broken on 32-bit as _PAGE_SWP_EXCLUSIVE there is _PAGE_PSE which would make exclusive swap entries pmd_present(). But CONFIG_ARCH_HAS_PMD_SOFTLEAVES is only selected for X86_64. Do we want some BUILD_BUG_ON() to catch if anyone would try to enable it for 32-bit machines? Otherwise: Reviewed-by: Kiryl Shutsemau (Meta) > #ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY > static inline pte_t pte_swp_mksoft_dirty(pte_t pte) > { > -- > 2.53.0-Meta > -- Kiryl Shutsemau / Kirill A. Shutemov