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[89.27.86.246]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5b8d46e0966sm191742e87.55.2026.09.21.22.34.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 21 Sep 2026 22:34:58 -0700 (PDT) From: mpenttil@redhat.com To: linux-mm@kvack.org Cc: dri-devel@lists.freedesktop.org, intel-xe@lists.freedesktop.org, linux-kernel@vger.kernel.org, =?UTF-8?q?Mika=20Penttil=C3=A4?= , David Hildenbrand , Jason Gunthorpe , Leon Romanovsky , Alistair Popple , Balbir Singh , Zi Yan , Matthew Brost , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko Subject: [PATCH v14 07/12] mm/hmm: migrate collection in HMM pagewalk - pmd level Date: Tue, 22 Sep 2026 08:34:16 +0300 Message-ID: <20260922053421.4092027-8-mpenttil@redhat.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260922053421.4092027-1-mpenttil@redhat.com> References: <20260922053421.4092027-1-mpenttil@redhat.com> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: lLKeYTdk2fqQ1oKzxsK6RUhekl221cJHDhsJ6DgwmZI_1790055300 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: intel-xe@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel Xe graphics driver List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-xe-bounces@lists.freedesktop.org Sender: "Intel-xe" From: Mika Penttilä Implement the needed hmm_vma_handle_migrate_prepare_pmd() function which is mostly carried over from migrate_device.c's migrate_vma_collect_huge_pmd() function. With HMM pagewalk based migration, the idea is that hmm_vma_handle_*() are responsible for faulting, and the pfn collecting part. hmm_vma_handle_migrate_prepare*() do the migration decisions (with HMM_PFN_MIGRATE), possibly split folios, and insert migration ptes/pmds. HMM pagewalk based migration is enabled in later commit, for now now hmm_select_migrate() returns 0. Cc: David Hildenbrand Cc: Jason Gunthorpe Cc: Leon Romanovsky Cc: Alistair Popple Cc: Balbir Singh Cc: Zi Yan Cc: Matthew Brost Suggested-by: Alistair Popple Signed-off-by: Mika Penttilä --- mm/hmm.c | 96 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 94 insertions(+), 2 deletions(-) diff --git a/mm/hmm.c b/mm/hmm.c index b3b79d13c797..a1459bd34c04 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -552,8 +552,100 @@ static int hmm_vma_handle_migrate_prepare_pmd(const struct mm_walk *walk, unsigned long end, unsigned long *hmm_pfn) { - // TODO: implement migration entry insertion - return 0; + struct hmm_vma_walk *hmm_vma_walk = walk->private; + struct hmm_range *range = hmm_vma_walk->range; + struct migrate_vma *migrate = range->migrate; + struct folio *fault_folio = NULL; + enum migrate_vma_info minfo; + struct folio *folio; + unsigned long i; + int r = 0; + + // Do we want to migrate at all? + minfo = hmm_select_migrate(range); + if (!minfo) + return r; + + WARN_ON_ONCE(!migrate); + HMM_ASSERT_PMD_LOCKED(hmm_vma_walk, true); + + fault_folio = migrate->fault_page ? + page_folio(migrate->fault_page) : NULL; + + if (pmd_none(*pmdp)) + return hmm_pfns_fill(start, end, hmm_vma_walk, 0); + + if (!(hmm_pfn[0] & HMM_PFN_VALID)) + goto out; + + if (pmd_trans_huge(*pmdp)) { + if (!(minfo & MIGRATE_VMA_SELECT_SYSTEM)) + goto out; + + folio = pmd_folio(*pmdp); + if (is_huge_zero_folio(folio)) + return hmm_pfns_fill(start, end, hmm_vma_walk, 0); + + } else if (!pmd_present(*pmdp)) { + const softleaf_t entry = softleaf_from_pmd(*pmdp); + + if (!softleaf_is_device_private(entry)) + goto out; + + if (!(minfo & MIGRATE_VMA_SELECT_DEVICE_PRIVATE)) + goto out; + + folio = softleaf_to_folio(entry); + if (folio->pgmap->owner != migrate->pgmap_owner) + goto out; + } else { + hmm_vma_walk->last = start; + return -EBUSY; + } + + folio_get(folio); + + if (folio != fault_folio && unlikely(!folio_trylock(folio))) { + folio_put(folio); + hmm_pfns_fill(start, end, hmm_vma_walk, HMM_PFN_ERROR); + return 0; + } + + if (thp_migration_supported() && + (migrate->flags & MIGRATE_VMA_SELECT_COMPOUND) && + (IS_ALIGNED(start, HPAGE_PMD_SIZE) && + IS_ALIGNED(end, HPAGE_PMD_SIZE))) { + struct page_vma_mapped_walk pvmw = { + .ptl = hmm_vma_walk->ptl, + .address = start, + .pmd = pmdp, + .vma = walk->vma, + }; + + hmm_pfn[0] |= HMM_PFN_MIGRATE | HMM_PFN_COMPOUND; + + r = set_pmd_migration_entry(&pvmw, folio_page(folio, 0)); + if (r) { + hmm_pfn[0] &= ~(HMM_PFN_MIGRATE | HMM_PFN_COMPOUND); + r = -ENOENT; // fallback + goto unlock_out; + } + for (i = 1, start += PAGE_SIZE; start < end; start += PAGE_SIZE, i++) + hmm_pfn[i] &= HMM_PFN_INOUT_FLAGS; + + } else { + r = -ENOENT; // fallback + goto unlock_out; + } + +out: + return r; + +unlock_out: + if (folio != fault_folio) + folio_unlock(folio); + folio_put(folio); + goto out; } /* -- 2.55.0