From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.subspace.kernel.org (Postfix) with ESMTP id D069860A4ACE for ; Wed, 21 Oct 2026 06:05:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=Hv398Jdk Received: by kanga.kvack.org (Postfix) id 75CC06B061B; Wed, 21 Oct 2026 02:05:46 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 6E6A26B061C; Wed, 21 Oct 2026 02:05:46 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 55FE96B061D; Wed, 21 Oct 2026 02:05:46 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 1C3636B061B for ; Wed, 21 Oct 2026 02:05:46 -0400 (EDT) Received: from smtpin20.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 81663A7CED for ; Wed, 21 Oct 2026 06:05:45 +0000 (UTC) X-FDA: 85345597050.20.15F5B0E Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf09.hostedemail.com (Postfix) with ESMTP id 416D4140005 for ; Wed, 21 Oct 2026 06:05:43 +0000 (UTC) Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=Hv398Jdk; dmarc=pass (policy=quarantine) header.from=redhat.com; spf=pass (imf09.hostedemail.com: domain of mpenttil@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=mpenttil@redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1792562743; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=p/7lyMAdO8fpbuawopvTUkUgysPqZTh82lxmIkmlslk=; b=TukMNDvw0BRdy/7hGyyVU/ExRkK2HCdjZ9pB4e77Oe+wPifKCH6bSTaicsIoWjr43jw15W ZvAg9iIm/lfkZq0iJO0EgONDuWrkojCdr3KounzXTUMIiWXDsRpANerYMsbioGaoCigH/E BQ73EvvII8f3g9gOnYSuY1xrc0NnFtY= ARC-Authentication-Results: i=1; imf09.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=Hv398Jdk; dmarc=pass (policy=quarantine) header.from=redhat.com; spf=pass (imf09.hostedemail.com: domain of mpenttil@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=mpenttil@redhat.com ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1792562743; b=ypH1f00w24ZRbBYWxayRwtjqdbieXllv8Iv91rg4p1p03Jd2Hlt8n+sljbatm7JQo/gT2k mDo33L19H5xkByI7cLYU1vNgPbprcZi1cSewLKK7z0LbQYC/0h3OP+N9h727bJn2ZkOBKX fm1ivUD/o+GprlHQwKaLoY/Ab1Y+P7k= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1792562742; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=p/7lyMAdO8fpbuawopvTUkUgysPqZTh82lxmIkmlslk=; b=Hv398JdkaivMdNbIkFYLQlLP2GluPez2sNWPUMtfioGdX6fGvKMw+zMMgyuSVEdCsT3f7H QsyM3yPQD3JVlOwp8UYOhAdP3h2jBT5CsmJ7puSAAEnT+4OCCCL1XNZxPrHP+XLTjIoShp X4+Yp0/hMRKFUYRuZ+1eGDPrkrqHk8s= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-316-fEnvGhJvMZOoR66e0jMggA-1; Wed, 21 Oct 2026 06:05:41 +0000 X-MC-Unique: fEnvGhJvMZOoR66e0jMggA-1 X-Mimecast-MFC-AGG-ID: fEnvGhJvMZOoR66e0jMggA_1792562740 Received: by mail-wm1-f69.google.com with SMTP id 5b1f17b1804b1-4a1dec05668so2433315e9.0 for ; Tue, 20 Oct 2026 23:05:41 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1792562740; x=1793167540; h=content-transfer-encoding:content-type:mime-version:references :in-reply-to:message-id:date:subject:cc:to:from:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=p/7lyMAdO8fpbuawopvTUkUgysPqZTh82lxmIkmlslk=; b=CIXvSHh9XMxI0zy59Yjl5v54tZLeBF7ZYh1vDlIaXscvjMIoBQz2ZXo9muFOcwPkrq g3nTp59dD+KeK8aYC9pfyRm/xXxsEcehekiAD1BRgexTkQZQNA0tF2XaysGvltV39K6y hvGWcN/k3lImuqCyZKobo9YmehhUA59toyai1VNxqq58gtOeF9Dzdzs6YFw8kWzNXKSh j4tqJSCgpIxvKD2jTNp1WFQWqqqGdaRUyxNdM1VSE6ZFLd9E4u0XN0BDIiylG5MXR0nY RcPpy/oCQxRvlvLdsrLYoCFjUkFP8XP88Pk2SR4EZvjzgBLtXgZobi34pxj209AAx+G2 ej9g== X-Gm-Message-State: AFq9FYI4ANOrjqtGjlHL0/U82cCcqQ6haOCp+Z9M/GoMdlMeKwfYqc1h 6uf0AiY2zZP/sBnlMBhYl1WxR2znA84VtkMBJgU4b+dNM1KsTPW5yUvQgefROqBoMzmmP1lW3or Prz6p0Os29qHYXxJr+I0ySAc/KIFhUKgJNjB5oSkGnd/5zyrJpO6yIKhgdWxNTtOmu1i8oaf/z8 OeaNJYjzGZ6twb+uob4gbeQkZXOnqbj7VptgXutA== X-Gm-Gg: AYBFou2hqfUw5/M3c2ZsFNFpwiFrgqI864CAGy6g6wrJINVF8Zxl9km/GtuzPkPg5Wy 8NqlLc5BgiscJGyeKQFR0iOWkaVXWMos9Ijxy2uVAuaUDW8YMInRUcVLHsP2FJyXtrYLM7DgEdT 7xI0+hlAL7hyEnHgjUKSvuudu9E3wuuQxMmARG2WdJZbJl/g6Cj1ZxQQrHvmBwe5nf1RK9z3kBL Hd+nojyXCcCYHcNJOEPh3pv5A3hFdjBT9fxR3cNcS8XGhkQJOnWxzXCuWHQCVfFGNT3cB+Q39ji J08rqjLwa2mrcWMoxWqC9v5gkuANU8pdLHz+AlxptWF7ULkJt32iyIx0LQMQpTdI6o8tBN28Pq3 sxVQnN3F2s+HrfcVDvYtD0Z4dLLw9PLCp9auN X-Received: by 2002:a05:600c:4e03:b0:49f:fe39:5bc8 with SMTP id 5b1f17b1804b1-4a1fdd14200mr14867985e9.12.1792562740332; Tue, 20 Oct 2026 23:05:40 -0700 (PDT) X-Received: by 2002:a05:600c:4e03:b0:49f:fe39:5bc8 with SMTP id 5b1f17b1804b1-4a1fdd14200mr14867095e9.12.1792562739786; Tue, 20 Oct 2026 23:05:39 -0700 (PDT) Received: from fedora.redhat.corp (89-27-86-246.bb.dnainternet.fi. [89.27.86.246]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48e254f02f1sm3413741f8f.3.2026.10.20.23.05.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 20 Oct 2026 23:05:38 -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 , Lyude Paul , Danilo Krummrich Subject: [PATCH v16 06/12] mm/hmm: migrate collection in HMM pagewalk - pmd level Date: Wed, 21 Oct 2026 09:05:00 +0300 Message-ID: <20261021060506.2377545-7-mpenttil@redhat.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20261021060506.2377545-1-mpenttil@redhat.com> References: <20261021060506.2377545-1-mpenttil@redhat.com> X-Archived-By: MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 4Gb5yeSs9NIhyAh4im9EkuOR48GMNTjiPyHPNt2zrtk_1792562740 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 416D4140005 X-Stat-Signature: qugyy7qtnyo7dnexyjkru7mzzuqruq8q X-Rspamd-Server: rspam06 X-Spam-Status: No, score=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Rspam-User: X-HE-Tag: 1792562743-829910 X-HE-Meta: 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 DU4Oll1F 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 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 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. Also avoid the problems present in the migrate_vma_collect_huge_pmd() split fallback path this HMM path supersedes: - extra refcount for fault_folio makes split_folio() fail - wrong folio unlocked after split_folio() 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 | 172 ++++++++++++++++++++++++++++++++++++++++++++++++------- 1 file changed, 151 insertions(+), 21 deletions(-) diff --git a/mm/hmm.c b/mm/hmm.c index 0ce947d0e572..5891efee3e18 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -492,31 +492,19 @@ static int hmm_vma_handle_absent_pmd(struct mm_walk *walk, unsigned long start, #ifdef CONFIG_DEVICE_MIGRATION /** - * migrate_vma_split_folio() - Helper function to split a THP folio + * __migrate_vma_split_folio() - split a folio and move the lock/ref to the + * order-0 folio backing @fault_page after the split * @folio: the folio to split - * @fault_page: struct page associated with the fault if any - * @hmm_vma_walk: walk in progress - * @ptep: pte_t * for unmap and unlock ptl + * @fault_page: fault page if any * - * Returns 0 on success + * Returns 0 on success. */ -static int migrate_vma_split_folio(struct folio *folio, - struct page *fault_page, - struct hmm_vma_walk *hmm_vma_walk, - pte_t *ptep) +static int __migrate_vma_split_folio(struct folio *folio, + struct page *fault_page) { - int ret; struct folio *fault_folio = fault_page ? page_folio(fault_page) : NULL; struct folio *new_fault_folio = NULL; - - if (folio != fault_folio) - folio_get(folio); - - pte_unmap_unlock(ptep, hmm_vma_walk->ptl); - hmm_vma_walk->ptelocked = false; - - if (folio != fault_folio) - folio_lock(folio); + int ret; ret = split_folio(folio); if (ret) { @@ -548,14 +536,145 @@ static int migrate_vma_split_folio(struct folio *folio, return 0; } +/** + * migrate_vma_split_folio() - drop the pte lock and split a THP folio + * @folio: the folio to split + * @fault_page: struct page associated with the fault if any + * @hmm_vma_walk: walk in progress + * @ptep: pte_t * for unmap and unlock ptl + * + * Returns 0 on success + */ +static int migrate_vma_split_folio(struct folio *folio, + struct page *fault_page, + struct hmm_vma_walk *hmm_vma_walk, + pte_t *ptep) +{ + struct folio *fault_folio = fault_page ? page_folio(fault_page) : NULL; + + if (folio != fault_folio) + folio_get(folio); + + pte_unmap_unlock(ptep, hmm_vma_walk->ptl); + hmm_vma_walk->ptelocked = false; + + if (folio != fault_folio) + folio_lock(folio); + + return __migrate_vma_split_folio(folio, fault_page); +} + static int hmm_vma_handle_migrate_prepare_pmd(const struct mm_walk *walk, pmd_t *pmdp, unsigned long start, 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); + goto split; /* fall back to splitting the pmd */ + } + for (i = 1, start += PAGE_SIZE; start < end; start += PAGE_SIZE, i++) + hmm_pfn[i] &= HMM_PFN_INOUT_FLAGS; + + } else { + goto split; /* fall back to splitting the pmd */ + } + +out: + return r; + +split: + spin_unlock(hmm_vma_walk->ptl); + hmm_vma_walk->pmdlocked = false; + + /* + * folio_get() above took an extra reference. For the fault folio the + * caller still holds a reference and the lock, which is the + * precondition of __migrate_vma_split_folio(), so drop the extra one. + */ + if (folio == fault_folio) + folio_put(folio); + + r = __migrate_vma_split_folio(folio, migrate->fault_page); + if (r) + return -EFAULT; + + hmm_vma_walk->last = start; + return -EBUSY; } /* @@ -958,6 +1077,17 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp, hmm_vma_walk->pmdlocked = false; } + /* + * hmm_vma_handle_migrate_prepare_pmd() splits the huge pmd in + * place when needed and returns -EBUSY to re-walk the range as + * PTEs; any other error means the split failed. + */ + if (r == -EBUSY) + return -EBUSY; + if (r) { + /* Split not successful, skip */ + return hmm_pfns_fill(start, end, hmm_vma_walk, HMM_PFN_ERROR); + } return r; } -- 2.55.0