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Tue, 03 Nov 2026 15:14:20 +0000 X-Mizu-Trace-ID: 198054973b778b6a X-Migadu-Flow: FLOW_OUT From: Usama Arif To: Lance Yang Cc: Usama Arif , akpm@linux-foundation.org, 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@linux.dev, 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, nico.pache@linux.dev, liam@infradead.org, ryan.roberts@arm.com, vbabka@kernel.org, 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 Subject: Re: [PATCH v8 00/30] mm: PMD-level swap entries for anonymous THPs Date: Tue, 3 Nov 2026 07:14:15 -0800 Message-ID: <20261103151416.1720617-1-usama.arif@linux.dev> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261004030844.90483-1-lance.yang@linux.dev> References: X-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: ymrqauhtug87utn5q7xif8crcyjjp698 X-Rspamd-Queue-Id: EB1EE1C0005 X-Rspam-User: X-Rspamd-Server: rspam08 X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1793718863-902039 X-HE-Meta: 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 tX1KZOGD L6q3PehTNW66CNAntZ+MOcLd2okU1CNPHuIMQCXRwMh4e71FPZtl0vXw/oa9Zr/kzxKXIhFbI6BVUOPnCRcCzpgG+gb2FbrFi+GMfkVnjSf8ICi5uJRDrlDU5xp82QiwX+0PD3iQzL+QkSmQb6GHoFSWsERgJEcOUhUMisiYWCI0IyYWHtyAZxRuxpqCy7ez91Jbu9ghv9xXZuw8GYzUrwvb3wM4m/WcWQOyJbi4tyIETkQbuwcF3ggY8Qg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Sun, 4 Oct 2026 11:08:44 +0800 Lance Yang wrote: > Hey Usama, > > Staring at the swap-entry bits across architectures, and RISC-V looks a > bit off in that regard ... > > With Svrsw60t59b and CONFIG_MEM_SOFT_DIRTY=y, setting swap soft-dirty also > sets _PAGE_EXEC. A migration PMD then looks present ... so the fault > handler skips the migration wait :( > > And yeah, this is a pre-existing bug. I've sent a separate fix for it. > Thanks for the fix! PMD swap entries also preserve soft-dirty, so the same encoding issue affects this series. The dependency note lists your separate fix for RISC-V with Svrsw60t59b and soft-dirty enabled. It applies cleanly and preserves the exclusive marker at bit 6. > https://lore.kernel.org/linux-mm/20261004030312.90163-1-lance.yang@linux.dev/ > > BTW, could we also add more checks to pmd_leaf_soft_dirty_tests() so we > catch this kind of issue early? Setting a swap flag shouldn't make a > non-present PMD present, IIUC. Done. The pgtable test now sets swap soft-dirty, checks that the flag is set, and checks that the PMD remains non-present. > > ---8<--- > diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c > index 863111c6d4eb..80686e2baaa1 100644 > --- a/mm/debug_vm_pgtable.c > +++ b/mm/debug_vm_pgtable.c > @@ -762,7 +762,9 @@ static void __init pmd_leaf_soft_dirty_tests(struct pgtable_debug_args *args) > WARN_ON(!pmd_is_huge(pmd)); > WARN_ON(!pmd_is_valid_softleaf(pmd)); > > - WARN_ON(!pmd_swp_soft_dirty(pmd_swp_mksoft_dirty(pmd))); > + pmd = pmd_swp_mksoft_dirty(pmd); > + WARN_ON(!pmd_swp_soft_dirty(pmd)); > + WARN_ON(pmd_present(pmd)); > WARN_ON(pmd_swp_soft_dirty(pmd_swp_clear_soft_dirty(pmd))); > } > #else /* !CONFIG_TRANSPARENT_HUGEPAGE */ > -- > > [...] > > Cheers, Lance >