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[85.23.51.1]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5a15602e692sm3263397e87.30.2026.03.15.23.24.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 15 Mar 2026 23:24:30 -0700 (PDT) From: mpenttil@redhat.com To: linux-mm@kvack.org Cc: 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 Subject: [PATCH v6 2/6] mm: Add helper to convert HMM pfn to migrate pfn Date: Mon, 16 Mar 2026 08:24:03 +0200 Message-ID: <20260316062407.3354636-3-mpenttil@redhat.com> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20260316062407.3354636-1-mpenttil@redhat.com> References: <20260316062407.3354636-1-mpenttil@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable From: Mika Penttil=C3=A4 The unified HMM/migrate_device pagewalk does the "collecting" in HMM side, so need a helper to transfer pfns to migrate_vma world. 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 Penttil=C3=A4 --- include/linux/hmm.h | 18 +++++++++-- include/linux/migrate.h | 3 +- mm/hmm.c | 6 ---- mm/migrate_device.c | 69 +++++++++++++++++++++++++++++++++++++++++ 4 files changed, 87 insertions(+), 9 deletions(-) diff --git a/include/linux/hmm.h b/include/linux/hmm.h index db75ffc949a7..b5418e318782 100644 --- a/include/linux/hmm.h +++ b/include/linux/hmm.h @@ -12,7 +12,7 @@ #include =20 struct mmu_interval_notifier; - +struct migrate_vma; /* * On output: * 0 - The page is faultable and a future call with=20 @@ -27,6 +27,7 @@ struct mmu_interval_notifier; * HMM_PFN_P2PDMA_BUS - Bus mapped P2P transfer * HMM_PFN_DMA_MAPPED - Flag preserved on input-to-output transformation * to mark that page is already DMA mapped + * HMM_PFN_MIGRATE - Migrate PTE installed * * On input: * 0 - Return the current state of the page, do not fault = it. @@ -34,6 +35,7 @@ struct mmu_interval_notifier; * will fail * HMM_PFN_REQ_WRITE - The output must have HMM_PFN_WRITE or hmm_range_fau= lt() * will fail. Must be combined with HMM_PFN_REQ_FAULT. + * HMM_PFN_REQ_MIGRATE - For default_flags, request to migrate to device */ enum hmm_pfn_flags { /* Output fields and flags */ @@ -48,15 +50,25 @@ enum hmm_pfn_flags { HMM_PFN_P2PDMA =3D 1UL << (BITS_PER_LONG - 5), HMM_PFN_P2PDMA_BUS =3D 1UL << (BITS_PER_LONG - 6), =20 - HMM_PFN_ORDER_SHIFT =3D (BITS_PER_LONG - 11), + /* Migrate request */ + HMM_PFN_MIGRATE =3D 1UL << (BITS_PER_LONG - 7), + HMM_PFN_COMPOUND =3D 1UL << (BITS_PER_LONG - 8), + HMM_PFN_ORDER_SHIFT =3D (BITS_PER_LONG - 13), =20 /* Input flags */ HMM_PFN_REQ_FAULT =3D HMM_PFN_VALID, HMM_PFN_REQ_WRITE =3D HMM_PFN_WRITE, + HMM_PFN_REQ_MIGRATE =3D HMM_PFN_MIGRATE, =20 HMM_PFN_FLAGS =3D ~((1UL << HMM_PFN_ORDER_SHIFT) - 1), }; =20 +enum { + /* These flags are carried from input-to-output */ + HMM_PFN_INOUT_FLAGS =3D HMM_PFN_DMA_MAPPED | HMM_PFN_P2PDMA | + HMM_PFN_P2PDMA_BUS, +}; + /* * hmm_pfn_to_page() - return struct page pointed to by a device entry * @@ -107,6 +119,7 @@ static inline unsigned int hmm_pfn_to_map_order(unsigne= d long hmm_pfn) * @default_flags: default flags for the range (write, read, ... see hmm d= oc) * @pfn_flags_mask: allows to mask pfn flags so that only default_flags ma= tter * @dev_private_owner: owner of device private pages + * @migrate: structure for migrating the associated vma */ struct hmm_range { struct mmu_interval_notifier *notifier; @@ -117,6 +130,7 @@ struct hmm_range { unsigned long default_flags; unsigned long pfn_flags_mask; void *dev_private_owner; + struct migrate_vma *migrate; }; =20 /* diff --git a/include/linux/migrate.h b/include/linux/migrate.h index d5af2b7f577b..425ab5242da0 100644 --- a/include/linux/migrate.h +++ b/include/linux/migrate.h @@ -3,6 +3,7 @@ #define _LINUX_MIGRATE_H =20 #include +#include #include #include #include @@ -200,7 +201,7 @@ void migrate_device_pages(unsigned long *src_pfns, unsi= gned long *dst_pfns, unsigned long npages); void migrate_device_finalize(unsigned long *src_pfns, unsigned long *dst_pfns, unsigned long npages); - +void migrate_hmm_range_setup(struct hmm_range *range); #endif /* CONFIG_MIGRATION */ =20 #endif /* _LINUX_MIGRATE_H */ diff --git a/mm/hmm.c b/mm/hmm.c index f6c4ddff4bd6..44699e28c551 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -41,12 +41,6 @@ enum { HMM_NEED_ALL_BITS =3D HMM_NEED_FAULT | HMM_NEED_WRITE_FAULT, }; =20 -enum { - /* These flags are carried from input-to-output */ - HMM_PFN_INOUT_FLAGS =3D HMM_PFN_DMA_MAPPED | HMM_PFN_P2PDMA | - HMM_PFN_P2PDMA_BUS, -}; - static int hmm_pfns_fill(unsigned long addr, unsigned long end, struct hmm_range *range, unsigned long cpu_flags) { diff --git a/mm/migrate_device.c b/mm/migrate_device.c index 8079676c8f1f..b320ea3736b4 100644 --- a/mm/migrate_device.c +++ b/mm/migrate_device.c @@ -1489,3 +1489,72 @@ int migrate_device_coherent_folio(struct folio *foli= o) return 0; return -EBUSY; } + +/** + * migrate_hmm_range_setup() - prepare to migrate a range of memory + * @range: contains pointer to migrate_vma to be populated + * + * When collecting happens by hmm_range_fault(), this populates + * the migrate->src[] and migrate->dst[] using range->hmm_pfns[]. + * Also, migrate->cpages and migrate->npages get initialized. + */ +void migrate_hmm_range_setup(struct hmm_range *range) +{ + + struct migrate_vma *migrate =3D range->migrate; + + if (!migrate) + return; + + migrate->npages =3D (migrate->end - migrate->start) >> PAGE_SHIFT; + migrate->cpages =3D 0; + + for (unsigned long i =3D 0; i < migrate->npages; i++) { + + unsigned long pfn =3D range->hmm_pfns[i]; + + pfn &=3D ~HMM_PFN_INOUT_FLAGS; + + /* + * + * Don't do migration if valid and migrate flags are not both set. + * + */ + if ((pfn & (HMM_PFN_VALID | HMM_PFN_MIGRATE)) !=3D + (HMM_PFN_VALID | HMM_PFN_MIGRATE)) { + migrate->src[i] =3D 0; + migrate->dst[i] =3D 0; + continue; + } + + migrate->cpages++; + + /* + * + * The zero page is encoded in a special way, valid and migrate is + * set, and pfn part is zero. Encode specially for migrate also. + * + */ + if (pfn =3D=3D (HMM_PFN_VALID|HMM_PFN_MIGRATE)) { + migrate->src[i] =3D MIGRATE_PFN_MIGRATE; + migrate->dst[i] =3D 0; + continue; + } + if (pfn =3D=3D (HMM_PFN_VALID|HMM_PFN_MIGRATE|HMM_PFN_COMPOUND)) { + migrate->src[i] =3D MIGRATE_PFN_MIGRATE|MIGRATE_PFN_COMPOUND; + migrate->dst[i] =3D 0; + continue; + } + + migrate->src[i] =3D migrate_pfn(page_to_pfn(hmm_pfn_to_page(pfn))) + | MIGRATE_PFN_MIGRATE; + migrate->src[i] |=3D (pfn & HMM_PFN_WRITE) ? MIGRATE_PFN_WRITE : 0; + migrate->src[i] |=3D (pfn & HMM_PFN_COMPOUND) ? MIGRATE_PFN_COMPOUND : 0; + migrate->dst[i] =3D 0; + } + + if (migrate->cpages) + migrate_vma_unmap(migrate); + +} +EXPORT_SYMBOL(migrate_hmm_range_setup); --=20 2.50.0