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[85.23.51.1]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5a3eee865e7sm3040666e87.10.2026.04.13.21.12.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 13 Apr 2026 21:12:56 -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 , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko Subject: [PATCH v8 1/5] mm/Kconfig: changes for migrate on fault for device pages Date: Tue, 14 Apr 2026 07:12:22 +0300 Message-ID: <20260414041226.1539439-2-mpenttil@redhat.com> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20260414041226.1539439-1-mpenttil@redhat.com> References: <20260414041226.1539439-1-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 HMM depends on MMU notifiers. With the unified HMM/migrate_device page table walk migrate_device needs HMM enabled. Enable them explicitly to avoid breaking random configs. Cc: Andrew Morton Cc: David Hildenbrand Cc: Lorenzo Stoakes Cc: "Liam R. Howlett" Cc: Vlastimil Babka Cc: Mike Rapoport Cc: Suren Baghdasaryan Cc: Michal Hocko Signed-off-by: Mika Penttil=C3=A4 Acked-by: David Hildenbrand (Arm) --- mm/Kconfig | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/Kconfig b/mm/Kconfig index ebd8ea353687..583d92bba2e8 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -647,6 +647,7 @@ config MIGRATION =20 config DEVICE_MIGRATION def_bool MIGRATION && ZONE_DEVICE + select HMM_MIRROR =20 config ARCH_ENABLE_HUGEPAGE_MIGRATION bool @@ -1222,6 +1223,7 @@ config ZONE_DEVICE config HMM_MIRROR bool depends on MMU + select MMU_NOTIFIER =20 config GET_FREE_REGION bool --=20 2.50.0 From nobody Tue Apr 14 13:59:22 2026 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EC46E313E38 for ; Tue, 14 Apr 2026 04:13:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; 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[85.23.51.1]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5a3eee865e7sm3040666e87.10.2026.04.13.21.13.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 13 Apr 2026 21:13:03 -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 , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko Subject: [PATCH v8 2/5] mm: Add helper to convert HMM pfn to migrate pfn Date: Tue, 14 Apr 2026 07:12:23 +0300 Message-ID: <20260414041226.1539439-3-mpenttil@redhat.com> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20260414041226.1539439-1-mpenttil@redhat.com> References: <20260414041226.1539439-1-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" on the HMM side, so we need a helper to transfer pfns to the 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 | 19 +++++++++++++- include/linux/migrate.h | 3 ++- mm/migrate_device.c | 55 +++++++++++++++++++++++++++++++++++++++++ 3 files changed, 75 insertions(+), 2 deletions(-) diff --git a/include/linux/hmm.h b/include/linux/hmm.h index db75ffc949a7..bfedafc1c143 100644 --- a/include/linux/hmm.h +++ b/include/linux/hmm.h @@ -13,6 +13,8 @@ =20 struct mmu_interval_notifier; =20 +struct migrate_vma; + /* * On output: * 0 - The page is faultable and a future call with=20 @@ -27,6 +29,13 @@ 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 - The entry is to be migrated. Note, HMM_PFN_MIGRATE + * alone without HMM_PFN_VALID denotes the + * empty page. + * This flag together with HMM_PFN_COMPOUND are + * indicators for migrate_hmm_range_setup() to + * setup the migrate pfns. + * HMM_PFN_COMPOUND - The entry is represents a > 0 order page * * On input: * 0 - Return the current state of the page, do not fault = it. @@ -34,6 +43,8 @@ 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, according = to + * hmm_range.migrate.flags */ enum hmm_pfn_flags { /* Output fields and flags */ @@ -48,11 +59,15 @@ 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), }; @@ -107,6 +122,7 @@ 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 a range of a VMA */ struct hmm_range { struct mmu_interval_notifier *notifier; @@ -117,6 +133,7 @@ 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/migrate_device.c b/mm/migrate_device.c index 8079676c8f1f..6c50cf2d80ca 100644 --- a/mm/migrate_device.c +++ b/mm/migrate_device.c @@ -1489,3 +1489,58 @@ 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 struct migrate_vma to be set up. + * + * When collecting has been done with hmm_range_fault(), this + * should be called next, and completes range->migrate by + * populating migrate->src[] and migrate->dst[] + * using range->hmm_pfns[]. + * Also, migrate->cpages and migrate->npages get initialized. + * After migrate_hmm_range_setup(), range->migrate is good + * for the rest of the migrate_vma_* flow. + */ +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]; + + /* + * We are only interested in entries to be + * migrated. + */ + if (!(pfn & HMM_PFN_MIGRATE)) { + migrate->src[i] =3D 0; + migrate->dst[i] =3D 0; + continue; + } + + migrate->cpages++; + + /* HMM_PFN_MIGRATE without HMM_PFN_VALID denotes the special zero page */ + if (pfn & (HMM_PFN_VALID)) + migrate->src[i] =3D migrate_pfn(page_to_pfn(hmm_pfn_to_page(pfn))) + | MIGRATE_PFN_MIGRATE; + else + migrate->src[i] =3D MIGRATE_PFN_MIGRATE; + + migrate->src[i] |=3D (pfn & HMM_PFN_WRITE) ? MIGRATE_PFN_WRITE : 0; + migrate->src[i] |=3D (pfn & HMM_PFN_COMPOUND) ? 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[85.23.51.1]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5a3eee865e7sm3040666e87.10.2026.04.13.21.13.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 13 Apr 2026 21:13:19 -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 , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko Subject: [PATCH v8 3/5] mm/hmm: do the plumbing for HMM to participate in migration Date: Tue, 14 Apr 2026 07:12:24 +0300 Message-ID: <20260414041226.1539439-4-mpenttil@redhat.com> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20260414041226.1539439-1-mpenttil@redhat.com> References: <20260414041226.1539439-1-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 Do the preparations in hmm_range_fault() and pagewalk callbacks to do the "collecting" part of migration, needed for migration on fault. These steps include locking for pmd/pte if migrating, capturing the vma for further migrate actions, and calling the still dummy hmm_vma_handle_migrate_prepare_pmd() and hmm_vma_handle_migrate_prepare() functions in the pagewalk. 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/migrate.h | 18 +- lib/test_hmm.c | 2 +- mm/hmm.c | 423 +++++++++++++++++++++++++++++++++++----- 3 files changed, 388 insertions(+), 55 deletions(-) diff --git a/include/linux/migrate.h b/include/linux/migrate.h index 425ab5242da0..07429027960a 100644 --- a/include/linux/migrate.h +++ b/include/linux/migrate.h @@ -106,6 +106,16 @@ static inline void softleaf_entry_wait_on_locked(softl= eaf_t entry, spinlock_t *p spin_unlock(ptl); } =20 +enum migrate_vma_info { + MIGRATE_VMA_SELECT_NONE =3D 0, + MIGRATE_VMA_SELECT_COMPOUND =3D MIGRATE_VMA_SELECT_NONE, +}; + +static inline enum migrate_vma_info hmm_select_migrate(struct hmm_range *r= ange) +{ + return MIGRATE_VMA_SELECT_NONE; +} + #endif /* CONFIG_MIGRATION */ =20 #ifdef CONFIG_NUMA_BALANCING @@ -149,7 +159,7 @@ static inline unsigned long migrate_pfn(unsigned long p= fn) return (pfn << MIGRATE_PFN_SHIFT) | MIGRATE_PFN_VALID; } =20 -enum migrate_vma_direction { +enum migrate_vma_info { MIGRATE_VMA_SELECT_SYSTEM =3D 1 << 0, MIGRATE_VMA_SELECT_DEVICE_PRIVATE =3D 1 << 1, MIGRATE_VMA_SELECT_DEVICE_COHERENT =3D 1 << 2, @@ -191,6 +201,12 @@ struct migrate_vma { struct page *fault_page; }; =20 +// TODO: enable migration +static inline enum migrate_vma_info hmm_select_migrate(struct hmm_range *r= ange) +{ + return 0; +} + int migrate_vma_setup(struct migrate_vma *args); void migrate_vma_pages(struct migrate_vma *migrate); void migrate_vma_finalize(struct migrate_vma *migrate); diff --git a/lib/test_hmm.c b/lib/test_hmm.c index 0964d53365e6..01aa0b60df2f 100644 --- a/lib/test_hmm.c +++ b/lib/test_hmm.c @@ -145,7 +145,7 @@ static bool dmirror_is_private_zone(struct dmirror_devi= ce *mdevice) HMM_DMIRROR_MEMORY_DEVICE_PRIVATE); } =20 -static enum migrate_vma_direction +static enum migrate_vma_info dmirror_select_device(struct dmirror *dmirror) { return (dmirror->mdevice->zone_device_type =3D=3D diff --git a/mm/hmm.c b/mm/hmm.c index 5955f2f0c83d..642593c3505f 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -20,6 +20,7 @@ #include #include #include +#include #include #include #include @@ -27,14 +28,44 @@ #include #include #include +#include =20 #include "internal.h" =20 struct hmm_vma_walk { - struct hmm_range *range; - unsigned long last; + struct mmu_notifier_range mmu_range; + struct vm_area_struct *vma; + struct hmm_range *range; + unsigned long start; + unsigned long end; + unsigned long last; + /* + * For migration we need pte/pmd + * locked for the handle_* and + * prepare_* regions. While faulting + * we have to drop the locks and + * start again. + * ptelocked and pmdlocked + * hold the state and tells if need + * to drop locks before faulting. + * ptl is the lock held for pte or pmd. + * + */ + bool ptelocked; + bool pmdlocked; + spinlock_t *ptl; }; =20 +#define HMM_ASSERT_PTE_LOCKED(hmm_vma_walk, locked) \ + WARN_ON_ONCE(hmm_vma_walk->ptelocked !=3D locked) + +#define HMM_ASSERT_PMD_LOCKED(hmm_vma_walk, locked) \ + WARN_ON_ONCE(hmm_vma_walk->pmdlocked !=3D locked) + +#define HMM_ASSERT_UNLOCKED(hmm_vma_walk) \ + WARN_ON_ONCE(hmm_vma_walk->ptelocked || \ + hmm_vma_walk->pmdlocked) + enum { HMM_NEED_FAULT =3D 1 << 0, HMM_NEED_WRITE_FAULT =3D 1 << 1, @@ -48,14 +79,37 @@ enum { }; =20 static int hmm_pfns_fill(unsigned long addr, unsigned long end, - struct hmm_range *range, unsigned long cpu_flags) + struct hmm_vma_walk *hmm_vma_walk, unsigned long cpu_flags) { + struct hmm_range *range =3D hmm_vma_walk->range; unsigned long i =3D (addr - range->start) >> PAGE_SHIFT; + enum migrate_vma_info minfo; + bool migrate =3D false; + + minfo =3D hmm_select_migrate(range); + if (cpu_flags !=3D HMM_PFN_ERROR) { + if (minfo && (vma_is_anonymous(hmm_vma_walk->vma))) { + cpu_flags |=3D HMM_PFN_MIGRATE; + migrate =3D true; + } + } + + if (migrate && thp_migration_supported() && + (minfo & MIGRATE_VMA_SELECT_COMPOUND) && + IS_ALIGNED(addr, HPAGE_PMD_SIZE) && + IS_ALIGNED(end, HPAGE_PMD_SIZE)) { + range->hmm_pfns[i] &=3D HMM_PFN_INOUT_FLAGS; + range->hmm_pfns[i] |=3D cpu_flags | HMM_PFN_COMPOUND; + addr +=3D PAGE_SIZE; + i++; + cpu_flags =3D 0; + } =20 for (; addr < end; addr +=3D PAGE_SIZE, i++) { range->hmm_pfns[i] &=3D HMM_PFN_INOUT_FLAGS; range->hmm_pfns[i] |=3D cpu_flags; } + return 0; } =20 @@ -78,6 +132,7 @@ static int hmm_vma_fault(unsigned long addr, unsigned lo= ng end, unsigned int fault_flags =3D FAULT_FLAG_REMOTE; =20 WARN_ON_ONCE(!required_fault); + HMM_ASSERT_UNLOCKED(hmm_vma_walk); hmm_vma_walk->last =3D addr; =20 if (required_fault & HMM_NEED_WRITE_FAULT) { @@ -171,11 +226,11 @@ static int hmm_vma_walk_hole(unsigned long addr, unsi= gned long end, if (!walk->vma) { if (required_fault) return -EFAULT; - return hmm_pfns_fill(addr, end, range, HMM_PFN_ERROR); + return hmm_pfns_fill(addr, end, hmm_vma_walk, HMM_PFN_ERROR); } if (required_fault) return hmm_vma_fault(addr, end, required_fault, walk); - return hmm_pfns_fill(addr, end, range, 0); + return hmm_pfns_fill(addr, end, hmm_vma_walk, 0); } =20 static inline unsigned long hmm_pfn_flags_order(unsigned long order) @@ -208,8 +263,13 @@ static int hmm_vma_handle_pmd(struct mm_walk *walk, un= signed long addr, cpu_flags =3D pmd_to_hmm_pfn_flags(range, pmd); required_fault =3D hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, cpu_flags); - if (required_fault) + if (required_fault) { + if (hmm_vma_walk->pmdlocked) { + spin_unlock(hmm_vma_walk->ptl); + hmm_vma_walk->pmdlocked =3D false; + } return hmm_vma_fault(addr, end, required_fault, walk); + } =20 pfn =3D pmd_pfn(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT); for (i =3D 0; addr < end; addr +=3D PAGE_SIZE, i++, pfn++) { @@ -289,14 +349,23 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, u= nsigned long addr, goto fault; =20 if (softleaf_is_migration(entry)) { - pte_unmap(ptep); - hmm_vma_walk->last =3D addr; - migration_entry_wait(walk->mm, pmdp, addr); - return -EBUSY; + if (!hmm_select_migrate(range)) { + HMM_ASSERT_UNLOCKED(hmm_vma_walk); + hmm_vma_walk->last =3D addr; + migration_entry_wait(walk->mm, pmdp, addr); + return -EBUSY; + } else + goto out; } =20 /* Report error for everything else */ - pte_unmap(ptep); + + if (hmm_vma_walk->ptelocked) { + pte_unmap_unlock(ptep, hmm_vma_walk->ptl); + hmm_vma_walk->ptelocked =3D false; + } else + pte_unmap(ptep); + return -EFAULT; } =20 @@ -313,7 +382,12 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, un= signed long addr, if (!vm_normal_page(walk->vma, addr, pte) && !is_zero_pfn(pte_pfn(pte))) { if (hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, 0)) { - pte_unmap(ptep); + if (hmm_vma_walk->ptelocked) { + pte_unmap_unlock(ptep, hmm_vma_walk->ptl); + hmm_vma_walk->ptelocked =3D false; + } else + pte_unmap(ptep); + return -EFAULT; } new_pfn_flags =3D HMM_PFN_ERROR; @@ -326,7 +400,11 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, un= signed long addr, return 0; =20 fault: - pte_unmap(ptep); + if (hmm_vma_walk->ptelocked) { + pte_unmap_unlock(ptep, hmm_vma_walk->ptl); + hmm_vma_walk->ptelocked =3D false; + } else + pte_unmap(ptep); /* Fault any virtual address we were asked to fault */ return hmm_vma_fault(addr, end, required_fault, walk); } @@ -370,13 +448,18 @@ static int hmm_vma_handle_absent_pmd(struct mm_walk *= walk, unsigned long start, required_fault =3D hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, 0); if (required_fault) { - if (softleaf_is_device_private(entry)) + if (softleaf_is_device_private(entry)) { + if (hmm_vma_walk->pmdlocked) { + spin_unlock(hmm_vma_walk->ptl); + hmm_vma_walk->pmdlocked =3D false; + } return hmm_vma_fault(addr, end, required_fault, walk); + } else return -EFAULT; } =20 - return hmm_pfns_fill(start, end, range, HMM_PFN_ERROR); + return hmm_pfns_fill(start, end, hmm_vma_walk, HMM_PFN_ERROR); } #else static int hmm_vma_handle_absent_pmd(struct mm_walk *walk, unsigned long s= tart, @@ -384,15 +467,100 @@ static int hmm_vma_handle_absent_pmd(struct mm_walk = *walk, unsigned long start, pmd_t pmd) { struct hmm_vma_walk *hmm_vma_walk =3D walk->private; - struct hmm_range *range =3D hmm_vma_walk->range; unsigned long npages =3D (end - start) >> PAGE_SHIFT; =20 if (hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, 0)) return -EFAULT; - return hmm_pfns_fill(start, end, range, HMM_PFN_ERROR); + return hmm_pfns_fill(start, end, hmm_vma_walk, HMM_PFN_ERROR); } #endif /* CONFIG_ARCH_ENABLE_THP_MIGRATION */ =20 +#ifdef CONFIG_DEVICE_MIGRATION +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; +} + +static int hmm_vma_handle_migrate_prepare(const struct mm_walk *walk, + pmd_t *pmdp, + pte_t *pte, + unsigned long addr, + unsigned long *hmm_pfn) +{ + // TODO: implement migration entry insertion + return 0; +} + +static int hmm_vma_walk_split(pmd_t *pmdp, + unsigned long addr, + struct mm_walk *walk) +{ + // TODO : implement split + return 0; +} + +#else +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) +{ + return 0; +} + +static int hmm_vma_handle_migrate_prepare(const struct mm_walk *walk, + pmd_t *pmdp, + pte_t *pte, + unsigned long addr, + unsigned long *hmm_pfn) +{ + return 0; +} + +static int hmm_vma_walk_split(pmd_t *pmdp, + unsigned long addr, + struct mm_walk *walk) +{ + return 0; +} +#endif + +static int hmm_vma_capture_migrate_range(unsigned long start, + unsigned long end, + struct mm_walk *walk) +{ + struct hmm_vma_walk *hmm_vma_walk =3D walk->private; + struct hmm_range *range =3D hmm_vma_walk->range; + + if (!hmm_select_migrate(range)) + return 0; + + if (hmm_vma_walk->vma && (hmm_vma_walk->vma !=3D walk->vma)) + return -ERANGE; + + hmm_vma_walk->vma =3D walk->vma; + hmm_vma_walk->start =3D start; + hmm_vma_walk->end =3D end; + + if (end - start > range->end - range->start) + return -ERANGE; + + if (!hmm_vma_walk->mmu_range.owner) { + mmu_notifier_range_init_owner(&hmm_vma_walk->mmu_range, MMU_NOTIFY_MIGRA= TE, 0, + walk->vma->vm_mm, start, end, + range->dev_private_owner); + mmu_notifier_invalidate_range_start(&hmm_vma_walk->mmu_range); + } + + return 0; +} + static int hmm_vma_walk_pmd(pmd_t *pmdp, unsigned long start, unsigned long end, @@ -400,46 +568,130 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp, { struct hmm_vma_walk *hmm_vma_walk =3D walk->private; struct hmm_range *range =3D hmm_vma_walk->range; - unsigned long *hmm_pfns =3D - &range->hmm_pfns[(start - range->start) >> PAGE_SHIFT]; unsigned long npages =3D (end - start) >> PAGE_SHIFT; + struct mm_struct *mm =3D walk->vma->vm_mm; + enum migrate_vma_info minfo; unsigned long addr =3D start; + unsigned long *hmm_pfns; + unsigned long i; pte_t *ptep; pmd_t pmd; + int r =3D 0; + + minfo =3D hmm_select_migrate(range); =20 again: - pmd =3D pmdp_get_lockless(pmdp); - if (pmd_none(pmd)) - return hmm_vma_walk_hole(start, end, -1, walk); + hmm_pfns =3D &range->hmm_pfns[(addr - range->start) >> PAGE_SHIFT]; + hmm_vma_walk->ptelocked =3D false; + hmm_vma_walk->pmdlocked =3D false; + + if (minfo) { + hmm_vma_walk->ptl =3D pmd_lock(mm, pmdp); + hmm_vma_walk->pmdlocked =3D true; + pmd =3D pmdp_get(pmdp); + } else + pmd =3D pmdp_get_lockless(pmdp); + + if (pmd_none(pmd)) { + r =3D hmm_vma_walk_hole(start, end, -1, walk); + + if (hmm_vma_walk->pmdlocked) { + spin_unlock(hmm_vma_walk->ptl); + hmm_vma_walk->pmdlocked =3D false; + } + return r; + } =20 if (thp_migration_supported() && pmd_is_migration_entry(pmd)) { - if (hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, 0)) { + if (!minfo) { + if (hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, 0)) { + hmm_vma_walk->last =3D addr; + pmd_migration_entry_wait(walk->mm, pmdp); + return -EBUSY; + } + } + for (i =3D 0; addr < end; addr +=3D PAGE_SIZE, i++) + hmm_pfns[i] &=3D HMM_PFN_INOUT_FLAGS; + + if (hmm_vma_walk->pmdlocked) { + spin_unlock(hmm_vma_walk->ptl); + hmm_vma_walk->pmdlocked =3D false; + } + + return 0; + } + + if (pmd_trans_huge(pmd) || !pmd_present(pmd)) { + + if (!pmd_present(pmd)) { + r =3D hmm_vma_handle_absent_pmd(walk, start, end, hmm_pfns, + pmd); + // If not migrating we are done + if (r || !minfo) { + if (hmm_vma_walk->pmdlocked) { + spin_unlock(hmm_vma_walk->ptl); + hmm_vma_walk->pmdlocked =3D false; + } + return r; + } + } + + if (pmd_trans_huge(pmd)) { + + /* + * No need to take pmd_lock here if not migrating, + * even if some other thread is splitting the huge + * pmd we will get that event through mmu_notifier callback. + * + * So just read pmd value and check again it's a transparent + * huge or device mapping one and compute corresponding pfn + * values. + */ + + if (!minfo) { + pmd =3D pmdp_get_lockless(pmdp); + if (!pmd_trans_huge(pmd)) + goto again; + } + + r =3D hmm_vma_handle_pmd(walk, addr, end, hmm_pfns, pmd); + + // If not migrating we are done + if (r || !minfo) { + if (hmm_vma_walk->pmdlocked) { + spin_unlock(hmm_vma_walk->ptl); + hmm_vma_walk->pmdlocked =3D false; + } + return r; + } + } + + r =3D hmm_vma_handle_migrate_prepare_pmd(walk, pmdp, start, end, hmm_pfn= s); + + if (hmm_vma_walk->pmdlocked) { + spin_unlock(hmm_vma_walk->ptl); + hmm_vma_walk->pmdlocked =3D false; + } + + if (r =3D=3D -ENOENT) { + r =3D hmm_vma_walk_split(pmdp, addr, walk); + if (r) { + /* Split not successful, skip */ + return hmm_pfns_fill(start, end, hmm_vma_walk, HMM_PFN_ERROR); + } + + /* Split successful, reloop */ hmm_vma_walk->last =3D addr; - pmd_migration_entry_wait(walk->mm, pmdp); return -EBUSY; } - return hmm_pfns_fill(start, end, range, 0); - } =20 - if (!pmd_present(pmd)) - return hmm_vma_handle_absent_pmd(walk, start, end, hmm_pfns, - pmd); + return r; =20 - if (pmd_trans_huge(pmd)) { - /* - * No need to take pmd_lock here, even if some other thread - * is splitting the huge pmd we will get that event through - * mmu_notifier callback. - * - * So just read pmd value and check again it's a transparent - * huge or device mapping one and compute corresponding pfn - * values. - */ - pmd =3D pmdp_get_lockless(pmdp); - if (!pmd_trans_huge(pmd)) - goto again; + } =20 - return hmm_vma_handle_pmd(walk, addr, end, hmm_pfns, pmd); + if (hmm_vma_walk->pmdlocked) { + spin_unlock(hmm_vma_walk->ptl); + hmm_vma_walk->pmdlocked =3D false; } =20 /* @@ -451,22 +703,43 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp, if (pmd_bad(pmd)) { if (hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, 0)) return -EFAULT; - return hmm_pfns_fill(start, end, range, HMM_PFN_ERROR); + return hmm_pfns_fill(start, end, hmm_vma_walk, HMM_PFN_ERROR); } =20 - ptep =3D pte_offset_map(pmdp, addr); + if (minfo) { + ptep =3D pte_offset_map_lock(mm, pmdp, addr, &hmm_vma_walk->ptl); + if (ptep) + hmm_vma_walk->ptelocked =3D true; + } else + ptep =3D pte_offset_map(pmdp, addr); if (!ptep) goto again; + for (; addr < end; addr +=3D PAGE_SIZE, ptep++, hmm_pfns++) { - int r; =20 r =3D hmm_vma_handle_pte(walk, addr, end, pmdp, ptep, hmm_pfns); if (r) { - /* hmm_vma_handle_pte() did pte_unmap() */ + /* hmm_vma_handle_pte() did pte_unmap() / pte_unmap_unlock */ return r; } + + r =3D hmm_vma_handle_migrate_prepare(walk, pmdp, ptep, addr, hmm_pfns); + if (r =3D=3D -EAGAIN) { + HMM_ASSERT_UNLOCKED(hmm_vma_walk); + goto again; + } + if (r) { + hmm_pfns_fill(addr, end, hmm_vma_walk, HMM_PFN_ERROR); + break; + } } - pte_unmap(ptep - 1); + + if (hmm_vma_walk->ptelocked) { + pte_unmap_unlock(ptep - 1, hmm_vma_walk->ptl); + hmm_vma_walk->ptelocked =3D false; + } else + pte_unmap(ptep - 1); + return 0; } =20 @@ -600,6 +873,11 @@ static int hmm_vma_walk_test(unsigned long start, unsi= gned long end, struct hmm_vma_walk *hmm_vma_walk =3D walk->private; struct hmm_range *range =3D hmm_vma_walk->range; struct vm_area_struct *vma =3D walk->vma; + int r; + + r =3D hmm_vma_capture_migrate_range(start, end, walk); + if (r) + return r; =20 if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)) && vma->vm_flags & VM_READ) @@ -622,7 +900,7 @@ static int hmm_vma_walk_test(unsigned long start, unsig= ned long end, (end - start) >> PAGE_SHIFT, 0)) return -EFAULT; =20 - hmm_pfns_fill(start, end, range, HMM_PFN_ERROR); + hmm_pfns_fill(start, end, hmm_vma_walk, HMM_PFN_ERROR); =20 /* Skip this vma and continue processing the next vma. */ return 1; @@ -652,9 +930,17 @@ static const struct mm_walk_ops hmm_walk_ops =3D { * the invalidation to finish. * -EFAULT: A page was requested to be valid and could not be made val= id * ie it has no backing VMA or it is illegal to access + * -ERANGE: The range crosses multiple VMAs, or space for hmm_pfns arr= ay + * is too low. * * This is similar to get_user_pages(), except that it can read the page t= ables * without mutating them (ie causing faults). + * + * If want to do migrate after faulting, call hmm_range_fault() with + * HMM_PFN_REQ_MIGRATE and initialize range.migrate field. + * After hmm_range_fault() call migrate_hmm_range_setup() instead of + * migrate_vma_setup() and after that follow normal migrate calls path. + * */ int hmm_range_fault(struct hmm_range *range) { @@ -662,16 +948,34 @@ int hmm_range_fault(struct hmm_range *range) .range =3D range, .last =3D range->start, }; - struct mm_struct *mm =3D range->notifier->mm; + struct mm_struct *mm; + bool is_fault_path; int ret; =20 + /* + * + * Could be serving a device fault or come from migrate + * entry point. For the former we have not resolved the vma + * yet, and the latter we don't have a notifier (but have a vma). + * + */ +#ifdef CONFIG_DEVICE_MIGRATION + is_fault_path =3D !!range->notifier; + mm =3D is_fault_path ? range->notifier->mm : range->migrate->vma->vm_mm; +#else + is_fault_path =3D true; + mm =3D range->notifier->mm; +#endif mmap_assert_locked(mm); =20 do { /* If range is no longer valid force retry. */ - if (mmu_interval_check_retry(range->notifier, - range->notifier_seq)) - return -EBUSY; + if (is_fault_path && mmu_interval_check_retry(range->notifier, + range->notifier_seq)) { + ret =3D -EBUSY; + break; + } + ret =3D walk_page_range(mm, hmm_vma_walk.last, range->end, &hmm_walk_ops, &hmm_vma_walk); /* @@ -681,6 +985,19 @@ int hmm_range_fault(struct hmm_range *range) * output, and all >=3D are still at their input values. */ } while (ret =3D=3D -EBUSY); + +#ifdef CONFIG_DEVICE_MIGRATION + if (hmm_select_migrate(range) && range->migrate && + hmm_vma_walk.mmu_range.owner) { + // The migrate_vma path has the following initialized + if (is_fault_path) { + range->migrate->vma =3D hmm_vma_walk.vma; 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[85.23.51.1]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5a3eee865e7sm3040666e87.10.2026.04.13.21.13.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 13 Apr 2026 21:13:25 -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 , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko Subject: [PATCH v8 4/5] mm: setup device page migration in HMM pagewalk Date: Tue, 14 Apr 2026 07:12:25 +0300 Message-ID: <20260414041226.1539439-5-mpenttil@redhat.com> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20260414041226.1539439-1-mpenttil@redhat.com> References: <20260414041226.1539439-1-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 Implement the needed hmm_vma_handle_migrate_prepare_pmd() and hmm_vma_handle_migrate_prepare() functions which are mostly carried over from migrate_device.c, as well as the needed split functions. Make migrate_device take use of HMM pagewalk for collecting part of migration. Also, remove the now unused migrate_vma_collect() functions. 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/migrate.h | 9 +- mm/hmm.c | 420 ++++++++++++++++++++++++++++++- mm/migrate_device.c | 534 ++-------------------------------------- 3 files changed, 438 insertions(+), 525 deletions(-) diff --git a/include/linux/migrate.h b/include/linux/migrate.h index 07429027960a..64d82bd16d3b 100644 --- a/include/linux/migrate.h +++ b/include/linux/migrate.h @@ -164,6 +164,7 @@ enum migrate_vma_info { MIGRATE_VMA_SELECT_DEVICE_PRIVATE =3D 1 << 1, MIGRATE_VMA_SELECT_DEVICE_COHERENT =3D 1 << 2, MIGRATE_VMA_SELECT_COMPOUND =3D 1 << 3, + MIGRATE_VMA_FAULT =3D 1 << 4, }; =20 struct migrate_vma { @@ -201,10 +202,14 @@ struct migrate_vma { struct page *fault_page; }; =20 -// TODO: enable migration static inline enum migrate_vma_info hmm_select_migrate(struct hmm_range *r= ange) { - return 0; + enum migrate_vma_info minfo; + + minfo =3D (range->default_flags & HMM_PFN_REQ_MIGRATE) ? + range->migrate->flags : 0; + + return minfo; } =20 int migrate_vma_setup(struct migrate_vma *args); diff --git a/mm/hmm.c b/mm/hmm.c index 642593c3505f..ce693938e5dc 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -476,34 +476,424 @@ static int hmm_vma_handle_absent_pmd(struct mm_walk = *walk, unsigned long start, #endif /* CONFIG_ARCH_ENABLE_THP_MIGRATION */ =20 #ifdef CONFIG_DEVICE_MIGRATION +/** + * migrate_vma_split_folio() - Helper function to split a THP folio + * @folio: the folio to split + * @fault_page: struct page associated with the fault if any + * + * Returns 0 on success + */ +static int migrate_vma_split_folio(struct folio *folio, + struct page *fault_page) +{ + int ret; + struct folio *fault_folio =3D fault_page ? page_folio(fault_page) : NULL; + struct folio *new_fault_folio =3D NULL; + + if (folio !=3D fault_folio) { + folio_get(folio); + folio_lock(folio); + } + + ret =3D split_folio(folio); + if (ret) { + if (folio !=3D fault_folio) { + folio_unlock(folio); + folio_put(folio); + } + return ret; + } + + new_fault_folio =3D fault_page ? page_folio(fault_page) : NULL; + + /* + * Ensure the lock is held on the correct + * folio after the split + */ + if (!new_fault_folio) { + folio_unlock(folio); + folio_put(folio); + } else if (folio !=3D new_fault_folio) { + if (new_fault_folio !=3D fault_folio) { + folio_get(new_fault_folio); + folio_lock(new_fault_folio); + } + folio_unlock(folio); + folio_put(folio); + } + + return 0; +} + 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 =3D walk->private; + struct hmm_range *range =3D hmm_vma_walk->range; + struct migrate_vma *migrate =3D range->migrate; + struct folio *fault_folio =3D NULL; + struct folio *folio; + enum migrate_vma_info minfo; + unsigned long i; + int r =3D 0; + + minfo =3D hmm_select_migrate(range); + if (!minfo) + return r; + + WARN_ON_ONCE(!migrate); + HMM_ASSERT_PMD_LOCKED(hmm_vma_walk, true); + + fault_folio =3D 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 =3D 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 =3D softleaf_from_pmd(*pmdp); + + folio =3D softleaf_to_folio(entry); + + if (!softleaf_is_device_private(entry)) + goto out; + + if (!(minfo & MIGRATE_VMA_SELECT_DEVICE_PRIVATE)) + goto out; + + if (folio->pgmap->owner !=3D migrate->pgmap_owner) + goto out; + + } else { + hmm_vma_walk->last =3D start; + return -EBUSY; + } + + folio_get(folio); + + if (folio !=3D 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 =3D { + .ptl =3D hmm_vma_walk->ptl, + .address =3D start, + .pmd =3D pmdp, + .vma =3D walk->vma, + }; + + hmm_pfn[0] |=3D HMM_PFN_MIGRATE | HMM_PFN_COMPOUND; + + r =3D set_pmd_migration_entry(&pvmw, folio_page(folio, 0)); + if (r) { + hmm_pfn[0] &=3D ~(HMM_PFN_MIGRATE | HMM_PFN_COMPOUND); + r =3D -ENOENT; // fallback + goto unlock_out; + } + for (i =3D 1, start +=3D PAGE_SIZE; start < end; start +=3D PAGE_SIZE, i= ++) + hmm_pfn[i] &=3D HMM_PFN_INOUT_FLAGS; + + } else { + r =3D -ENOENT; // fallback + goto unlock_out; + } + + +out: + return r; + +unlock_out: + if (folio !=3D fault_folio) + folio_unlock(folio); + folio_put(folio); + goto out; } =20 +/* + * Install migration entries if migration requested, either from fault + * or migrate paths. + * + */ static int hmm_vma_handle_migrate_prepare(const struct mm_walk *walk, pmd_t *pmdp, - pte_t *pte, + pte_t *ptep, unsigned long addr, - unsigned long *hmm_pfn) + unsigned long *hmm_pfn, + bool *unmapped) { - // TODO: implement migration entry insertion + struct hmm_vma_walk *hmm_vma_walk =3D walk->private; + struct hmm_range *range =3D hmm_vma_walk->range; + struct migrate_vma *migrate =3D range->migrate; + struct mm_struct *mm =3D walk->vma->vm_mm; + struct folio *fault_folio =3D NULL; + enum migrate_vma_info minfo; + struct dev_pagemap *pgmap; + bool anon_exclusive; + struct folio *folio; + unsigned long pfn; + struct page *page; + softleaf_t entry; + pte_t pte, swp_pte; + bool writable =3D false; + + // Do we want to migrate at all? + minfo =3D hmm_select_migrate(range); + if (!minfo) + return 0; + + WARN_ON_ONCE(!migrate); + HMM_ASSERT_PTE_LOCKED(hmm_vma_walk, true); + + fault_folio =3D migrate->fault_page ? + page_folio(migrate->fault_page) : NULL; + + pte =3D ptep_get(ptep); + + if (pte_none(pte)) { + // migrate without faulting case + if (vma_is_anonymous(walk->vma)) { + *hmm_pfn &=3D HMM_PFN_INOUT_FLAGS; + *hmm_pfn |=3D HMM_PFN_MIGRATE; + goto out; + } + } + + if (!(hmm_pfn[0] & HMM_PFN_VALID)) + goto out; + + if (!pte_present(pte)) { + /* + * Only care about unaddressable device page special + * page table entry. Other special swap entries are not + * migratable, and we ignore regular swapped page. + */ + entry =3D softleaf_from_pte(pte); + if (!softleaf_is_device_private(entry)) + goto out; + + if (!(minfo & MIGRATE_VMA_SELECT_DEVICE_PRIVATE)) + goto out; + + page =3D softleaf_to_page(entry); + folio =3D page_folio(page); + if (folio->pgmap->owner !=3D migrate->pgmap_owner) + goto out; + + if (folio_test_large(folio)) { + int ret; + + pte_unmap_unlock(ptep, hmm_vma_walk->ptl); + hmm_vma_walk->ptelocked =3D false; + ret =3D migrate_vma_split_folio(folio, + migrate->fault_page); + if (ret) + goto out_error; + return -EAGAIN; + } + + pfn =3D page_to_pfn(page); + if (softleaf_is_device_private_write(entry)) + writable =3D true; + } else { + pfn =3D pte_pfn(pte); + if (is_zero_pfn(pfn) && + (minfo & MIGRATE_VMA_SELECT_SYSTEM)) { + *hmm_pfn =3D HMM_PFN_MIGRATE; + goto out; + } + page =3D vm_normal_page(walk->vma, addr, pte); + if (page && !is_zone_device_page(page) && + !(minfo & MIGRATE_VMA_SELECT_SYSTEM)) { + goto out; + } else if (page && is_device_coherent_page(page)) { + pgmap =3D page_pgmap(page); + + if (!(minfo & + MIGRATE_VMA_SELECT_DEVICE_COHERENT) || + pgmap->owner !=3D migrate->pgmap_owner) + goto out; + } + + folio =3D page ? page_folio(page) : NULL; + if (folio && folio_test_large(folio)) { + int ret; + + pte_unmap_unlock(ptep, hmm_vma_walk->ptl); + hmm_vma_walk->ptelocked =3D false; + + ret =3D migrate_vma_split_folio(folio, + migrate->fault_page); + if (ret) + goto out_error; + return -EAGAIN; + } + + writable =3D pte_write(pte); + } + + if (!page || !page->mapping) + goto out; + + /* + * By getting a reference on the folio we pin it and that blocks + * any kind of migration. Side effect is that it "freezes" the + * pte. + * + * We drop this reference after isolating the folio from the lru + * for non device folio (device folio are not on the lru and thus + * can't be dropped from it). + */ + folio =3D page_folio(page); + folio_get(folio); + + /* + * We rely on folio_trylock() to avoid deadlock between + * concurrent migrations where each is waiting on the others + * folio lock. If we can't immediately lock the folio we fail this + * migration as it is only best effort anyway. + * + * If we can lock the folio it's safe to set up a migration entry + * now. In the common case where the folio is mapped once in a + * single process setting up the migration entry now is an + * optimisation to avoid walking the rmap later with + * try_to_migrate(). + */ + + if (fault_folio =3D=3D folio || folio_trylock(folio)) { + anon_exclusive =3D folio_test_anon(folio) && + PageAnonExclusive(page); + + flush_cache_page(walk->vma, addr, pfn); + + if (anon_exclusive) { + pte =3D ptep_clear_flush(walk->vma, addr, ptep); + + if (folio_try_share_anon_rmap_pte(folio, page)) { + set_pte_at(mm, addr, ptep, pte); + folio_unlock(folio); + folio_put(folio); + goto out; + } + } else { + pte =3D ptep_get_and_clear(mm, addr, ptep); + } + + if (pte_dirty(pte)) + folio_mark_dirty(folio); + + /* Setup special migration page table entry */ + if (writable) + entry =3D make_writable_migration_entry(pfn); + else if (anon_exclusive) + entry =3D make_readable_exclusive_migration_entry(pfn); + else + entry =3D make_readable_migration_entry(pfn); + + if (pte_present(pte)) { + if (pte_young(pte)) + entry =3D make_migration_entry_young(entry); + if (pte_dirty(pte)) + entry =3D make_migration_entry_dirty(entry); + } + + swp_pte =3D swp_entry_to_pte(entry); + if (pte_present(pte)) { + if (pte_soft_dirty(pte)) + swp_pte =3D pte_swp_mksoft_dirty(swp_pte); + if (pte_uffd_wp(pte)) + swp_pte =3D pte_swp_mkuffd_wp(swp_pte); + } else { + if (pte_swp_soft_dirty(pte)) + swp_pte =3D pte_swp_mksoft_dirty(swp_pte); + if (pte_swp_uffd_wp(pte)) + swp_pte =3D pte_swp_mkuffd_wp(swp_pte); + } + + set_pte_at(mm, addr, ptep, swp_pte); + folio_remove_rmap_pte(folio, page, walk->vma); + folio_put(folio); + *hmm_pfn |=3D HMM_PFN_MIGRATE; + + if (pte_present(pte)) + *unmapped =3D true; + } else + folio_put(folio); +out: return 0; +out_error: + return -EFAULT; } =20 static int hmm_vma_walk_split(pmd_t *pmdp, unsigned long addr, struct mm_walk *walk) { - // TODO : implement split - return 0; -} + struct hmm_vma_walk *hmm_vma_walk =3D walk->private; + struct hmm_range *range =3D hmm_vma_walk->range; + struct migrate_vma *migrate =3D range->migrate; + struct folio *folio, *fault_folio; + spinlock_t *ptl; + int ret =3D 0; =20 + HMM_ASSERT_UNLOCKED(hmm_vma_walk); + + fault_folio =3D (migrate && migrate->fault_page) ? + page_folio(migrate->fault_page) : NULL; + + ptl =3D pmd_lock(walk->mm, pmdp); + if (unlikely(!pmd_trans_huge(*pmdp))) { + spin_unlock(ptl); + goto out; + } + + folio =3D pmd_folio(*pmdp); + if (is_huge_zero_folio(folio)) { + spin_unlock(ptl); + split_huge_pmd(walk->vma, pmdp, addr); + } else { + folio_get(folio); + spin_unlock(ptl); + + if (folio !=3D fault_folio) { + if (unlikely(!folio_trylock(folio))) { + folio_put(folio); + ret =3D -EBUSY; + goto out; + } + } else + folio_put(folio); + + ret =3D split_folio(folio); + if (fault_folio !=3D folio) { + folio_unlock(folio); + folio_put(folio); + } + + } +out: + return ret; +} #else static int hmm_vma_handle_migrate_prepare_pmd(const struct mm_walk *walk, pmd_t *pmdp, @@ -518,7 +908,8 @@ static int hmm_vma_handle_migrate_prepare(const struct = mm_walk *walk, pmd_t *pmdp, pte_t *pte, unsigned long addr, - unsigned long *hmm_pfn) + unsigned long *hmm_pfn, + bool *unmapped) { return 0; } @@ -573,6 +964,7 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp, enum migrate_vma_info minfo; unsigned long addr =3D start; unsigned long *hmm_pfns; + bool unmapped =3D false; unsigned long i; pte_t *ptep; pmd_t pmd; @@ -654,7 +1046,7 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp, goto again; } =20 - r =3D hmm_vma_handle_pmd(walk, addr, end, hmm_pfns, pmd); + r =3D hmm_vma_handle_pmd(walk, start, end, hmm_pfns, pmd); =20 // If not migrating we are done if (r || !minfo) { @@ -723,9 +1115,13 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp, return r; } =20 - r =3D hmm_vma_handle_migrate_prepare(walk, pmdp, ptep, addr, hmm_pfns); + r =3D hmm_vma_handle_migrate_prepare(walk, pmdp, ptep, addr, hmm_pfns, &= unmapped); if (r =3D=3D -EAGAIN) { HMM_ASSERT_UNLOCKED(hmm_vma_walk); + if (unmapped) { + flush_tlb_range(walk->vma, start, addr); + unmapped =3D false; + } goto again; } if (r) { @@ -733,6 +1129,8 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp, break; } } + if (unmapped) + flush_tlb_range(walk->vma, start, addr); =20 if (hmm_vma_walk->ptelocked) { pte_unmap_unlock(ptep - 1, hmm_vma_walk->ptl); diff --git a/mm/migrate_device.c b/mm/migrate_device.c index 6c50cf2d80ca..0de53b50d841 100644 --- a/mm/migrate_device.c +++ b/mm/migrate_device.c @@ -18,514 +18,6 @@ #include #include "internal.h" =20 -static int migrate_vma_collect_skip(unsigned long start, - unsigned long end, - struct mm_walk *walk) -{ - struct migrate_vma *migrate =3D walk->private; - unsigned long addr; - - for (addr =3D start; addr < end; addr +=3D PAGE_SIZE) { - migrate->dst[migrate->npages] =3D 0; - migrate->src[migrate->npages++] =3D 0; - } - - return 0; -} - -static int migrate_vma_collect_hole(unsigned long start, - unsigned long end, - __always_unused int depth, - struct mm_walk *walk) -{ - struct migrate_vma *migrate =3D walk->private; - unsigned long addr; - - /* Only allow populating anonymous memory. */ - if (!vma_is_anonymous(walk->vma)) - return migrate_vma_collect_skip(start, end, walk); - - if (thp_migration_supported() && - (migrate->flags & MIGRATE_VMA_SELECT_COMPOUND) && - (IS_ALIGNED(start, HPAGE_PMD_SIZE) && - IS_ALIGNED(end, HPAGE_PMD_SIZE))) { - migrate->src[migrate->npages] =3D MIGRATE_PFN_MIGRATE | - MIGRATE_PFN_COMPOUND; - migrate->dst[migrate->npages] =3D 0; - migrate->npages++; - migrate->cpages++; - - /* - * Collect the remaining entries as holes, in case we - * need to split later - */ - return migrate_vma_collect_skip(start + PAGE_SIZE, end, walk); - } - - for (addr =3D start; addr < end; addr +=3D PAGE_SIZE) { - migrate->src[migrate->npages] =3D MIGRATE_PFN_MIGRATE; - migrate->dst[migrate->npages] =3D 0; - migrate->npages++; - migrate->cpages++; - } - - return 0; -} - -/** - * migrate_vma_split_folio() - Helper function to split a THP folio - * @folio: the folio to split - * @fault_page: struct page associated with the fault if any - * - * Returns 0 on success - */ -static int migrate_vma_split_folio(struct folio *folio, - struct page *fault_page) -{ - int ret; - struct folio *fault_folio =3D fault_page ? page_folio(fault_page) : NULL; - struct folio *new_fault_folio =3D NULL; - - if (folio !=3D fault_folio) { - folio_get(folio); - folio_lock(folio); - } - - ret =3D split_folio(folio); - if (ret) { - if (folio !=3D fault_folio) { - folio_unlock(folio); - folio_put(folio); - } - return ret; - } - - new_fault_folio =3D fault_page ? page_folio(fault_page) : NULL; - - /* - * Ensure the lock is held on the correct - * folio after the split - */ - if (!new_fault_folio) { - folio_unlock(folio); - folio_put(folio); - } else if (folio !=3D new_fault_folio) { - if (new_fault_folio !=3D fault_folio) { - folio_get(new_fault_folio); - folio_lock(new_fault_folio); - } - folio_unlock(folio); - folio_put(folio); - } - - return 0; -} - -/** migrate_vma_collect_huge_pmd - collect THP pages without splitting the - * folio for device private pages. - * @pmdp: pointer to pmd entry - * @start: start address of the range for migration - * @end: end address of the range for migration - * @walk: mm_walk callback structure - * @fault_folio: folio associated with the fault if any - * - * Collect the huge pmd entry at @pmdp for migration and set the - * MIGRATE_PFN_COMPOUND flag in the migrate src entry to indicate that - * migration will occur at HPAGE_PMD granularity - */ -static int migrate_vma_collect_huge_pmd(pmd_t *pmdp, unsigned long start, - unsigned long end, struct mm_walk *walk, - struct folio *fault_folio) -{ - struct mm_struct *mm =3D walk->mm; - struct folio *folio; - struct migrate_vma *migrate =3D walk->private; - spinlock_t *ptl; - int ret; - unsigned long write =3D 0; - - ptl =3D pmd_lock(mm, pmdp); - if (pmd_none(*pmdp)) { - spin_unlock(ptl); - return migrate_vma_collect_hole(start, end, -1, walk); - } - - if (pmd_trans_huge(*pmdp)) { - if (!(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM)) { - spin_unlock(ptl); - return migrate_vma_collect_skip(start, end, walk); - } - - folio =3D pmd_folio(*pmdp); - if (is_huge_zero_folio(folio)) { - spin_unlock(ptl); - return migrate_vma_collect_hole(start, end, -1, walk); - } - if (pmd_write(*pmdp)) - write =3D MIGRATE_PFN_WRITE; - } else if (!pmd_present(*pmdp)) { - const softleaf_t entry =3D softleaf_from_pmd(*pmdp); - - folio =3D softleaf_to_folio(entry); - - if (!softleaf_is_device_private(entry) || - !(migrate->flags & MIGRATE_VMA_SELECT_DEVICE_PRIVATE) || - (folio->pgmap->owner !=3D migrate->pgmap_owner)) { - spin_unlock(ptl); - return migrate_vma_collect_skip(start, end, walk); - } - - if (softleaf_is_migration(entry)) { - softleaf_entry_wait_on_locked(entry, ptl); - spin_unlock(ptl); - return -EAGAIN; - } - - if (softleaf_is_device_private_write(entry)) - write =3D MIGRATE_PFN_WRITE; - } else { - spin_unlock(ptl); - return -EAGAIN; - } - - folio_get(folio); - if (folio !=3D fault_folio && unlikely(!folio_trylock(folio))) { - spin_unlock(ptl); - folio_put(folio); - return migrate_vma_collect_skip(start, end, walk); - } - - 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 =3D { - .ptl =3D ptl, - .address =3D start, - .pmd =3D pmdp, - .vma =3D walk->vma, - }; - - unsigned long pfn =3D page_to_pfn(folio_page(folio, 0)); - - migrate->src[migrate->npages] =3D migrate_pfn(pfn) | write - | MIGRATE_PFN_MIGRATE - | MIGRATE_PFN_COMPOUND; - migrate->dst[migrate->npages++] =3D 0; - migrate->cpages++; - ret =3D set_pmd_migration_entry(&pvmw, folio_page(folio, 0)); - if (ret) { - migrate->npages--; - migrate->cpages--; - migrate->src[migrate->npages] =3D 0; - migrate->dst[migrate->npages] =3D 0; - goto fallback; - } - migrate_vma_collect_skip(start + PAGE_SIZE, end, walk); - spin_unlock(ptl); - return 0; - } - -fallback: - spin_unlock(ptl); - if (!folio_test_large(folio)) - goto done; - ret =3D split_folio(folio); - if (fault_folio !=3D folio) - folio_unlock(folio); - folio_put(folio); - if (ret) - return migrate_vma_collect_skip(start, end, walk); - if (pmd_none(pmdp_get_lockless(pmdp))) - return migrate_vma_collect_hole(start, end, -1, walk); - -done: - return -ENOENT; -} - -static int migrate_vma_collect_pmd(pmd_t *pmdp, - unsigned long start, - unsigned long end, - struct mm_walk *walk) -{ - struct migrate_vma *migrate =3D walk->private; - struct vm_area_struct *vma =3D walk->vma; - struct mm_struct *mm =3D vma->vm_mm; - unsigned long addr =3D start, unmapped =3D 0; - spinlock_t *ptl; - struct folio *fault_folio =3D migrate->fault_page ? - page_folio(migrate->fault_page) : NULL; - pte_t *ptep; - -again: - if (pmd_trans_huge(*pmdp) || !pmd_present(*pmdp)) { - int ret =3D migrate_vma_collect_huge_pmd(pmdp, start, end, walk, fault_f= olio); - - if (ret =3D=3D -EAGAIN) - goto again; - if (ret =3D=3D 0) - return 0; - } - - ptep =3D pte_offset_map_lock(mm, pmdp, start, &ptl); - if (!ptep) - goto again; - lazy_mmu_mode_enable(); - ptep +=3D (addr - start) / PAGE_SIZE; - - for (; addr < end; addr +=3D PAGE_SIZE, ptep++) { - struct dev_pagemap *pgmap; - unsigned long mpfn =3D 0, pfn; - struct folio *folio; - struct page *page; - softleaf_t entry; - pte_t pte; - - pte =3D ptep_get(ptep); - - if (pte_none(pte)) { - if (vma_is_anonymous(vma)) { - mpfn =3D MIGRATE_PFN_MIGRATE; - migrate->cpages++; - } - goto next; - } - - if (!pte_present(pte)) { - /* - * Only care about unaddressable device page special - * page table entry. Other special swap entries are not - * migratable, and we ignore regular swapped page. - */ - entry =3D softleaf_from_pte(pte); - if (!softleaf_is_device_private(entry)) - goto next; - - page =3D softleaf_to_page(entry); - pgmap =3D page_pgmap(page); - if (!(migrate->flags & - MIGRATE_VMA_SELECT_DEVICE_PRIVATE) || - pgmap->owner !=3D migrate->pgmap_owner) - goto next; - - folio =3D page_folio(page); - if (folio_test_large(folio)) { - int ret; - - lazy_mmu_mode_disable(); - pte_unmap_unlock(ptep, ptl); - ret =3D migrate_vma_split_folio(folio, - migrate->fault_page); - - if (ret) { - if (unmapped) - flush_tlb_range(walk->vma, start, end); - - return migrate_vma_collect_skip(addr, end, walk); - } - - goto again; - } - - mpfn =3D migrate_pfn(page_to_pfn(page)) | - MIGRATE_PFN_MIGRATE; - if (softleaf_is_device_private_write(entry)) - mpfn |=3D MIGRATE_PFN_WRITE; - } else { - pfn =3D pte_pfn(pte); - if (is_zero_pfn(pfn) && - (migrate->flags & MIGRATE_VMA_SELECT_SYSTEM)) { - mpfn =3D MIGRATE_PFN_MIGRATE; - migrate->cpages++; - goto next; - } - page =3D vm_normal_page(migrate->vma, addr, pte); - if (page && !is_zone_device_page(page) && - !(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM)) { - goto next; - } else if (page && is_device_coherent_page(page)) { - pgmap =3D page_pgmap(page); - - if (!(migrate->flags & - MIGRATE_VMA_SELECT_DEVICE_COHERENT) || - pgmap->owner !=3D migrate->pgmap_owner) - goto next; - } - folio =3D page ? page_folio(page) : NULL; - if (folio && folio_test_large(folio)) { - int ret; - - lazy_mmu_mode_disable(); - pte_unmap_unlock(ptep, ptl); - ret =3D migrate_vma_split_folio(folio, - migrate->fault_page); - - if (ret) { - if (unmapped) - flush_tlb_range(walk->vma, start, end); - - return migrate_vma_collect_skip(addr, end, walk); - } - - goto again; - } - mpfn =3D migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE; - mpfn |=3D pte_write(pte) ? MIGRATE_PFN_WRITE : 0; - } - - if (!page || !page->mapping) { - mpfn =3D 0; - goto next; - } - - /* - * By getting a reference on the folio we pin it and that blocks - * any kind of migration. Side effect is that it "freezes" the - * pte. - * - * We drop this reference after isolating the folio from the lru - * for non device folio (device folio are not on the lru and thus - * can't be dropped from it). - */ - folio =3D page_folio(page); - folio_get(folio); - - /* - * We rely on folio_trylock() to avoid deadlock between - * concurrent migrations where each is waiting on the others - * folio lock. If we can't immediately lock the folio we fail this - * migration as it is only best effort anyway. - * - * If we can lock the folio it's safe to set up a migration entry - * now. In the common case where the folio is mapped once in a - * single process setting up the migration entry now is an - * optimisation to avoid walking the rmap later with - * try_to_migrate(). - */ - if (fault_folio =3D=3D folio || folio_trylock(folio)) { - bool anon_exclusive; - pte_t swp_pte; - - flush_cache_page(vma, addr, pte_pfn(pte)); - anon_exclusive =3D folio_test_anon(folio) && - PageAnonExclusive(page); - if (anon_exclusive) { - pte =3D ptep_clear_flush(vma, addr, ptep); - - if (folio_try_share_anon_rmap_pte(folio, page)) { - set_pte_at(mm, addr, ptep, pte); - if (fault_folio !=3D folio) - folio_unlock(folio); - folio_put(folio); - mpfn =3D 0; - goto next; - } - } else { - pte =3D ptep_get_and_clear(mm, addr, ptep); - } - - migrate->cpages++; - - /* Set the dirty flag on the folio now the pte is gone. */ - if (pte_dirty(pte)) - folio_mark_dirty(folio); - - /* Setup special migration page table entry */ - if (mpfn & MIGRATE_PFN_WRITE) - entry =3D make_writable_migration_entry( - page_to_pfn(page)); - else if (anon_exclusive) - entry =3D make_readable_exclusive_migration_entry( - page_to_pfn(page)); - else - entry =3D make_readable_migration_entry( - page_to_pfn(page)); - if (pte_present(pte)) { - if (pte_young(pte)) - entry =3D make_migration_entry_young(entry); - if (pte_dirty(pte)) - entry =3D make_migration_entry_dirty(entry); - } - swp_pte =3D swp_entry_to_pte(entry); - if (pte_present(pte)) { - if (pte_soft_dirty(pte)) - swp_pte =3D pte_swp_mksoft_dirty(swp_pte); - if (pte_uffd_wp(pte)) - swp_pte =3D pte_swp_mkuffd_wp(swp_pte); - } else { - if (pte_swp_soft_dirty(pte)) - swp_pte =3D pte_swp_mksoft_dirty(swp_pte); - if (pte_swp_uffd_wp(pte)) - swp_pte =3D pte_swp_mkuffd_wp(swp_pte); - } - set_pte_at(mm, addr, ptep, swp_pte); - - /* - * This is like regular unmap: we remove the rmap and - * drop the folio refcount. The folio won't be freed, as - * we took a reference just above. - */ - folio_remove_rmap_pte(folio, page, vma); - folio_put(folio); - - if (pte_present(pte)) - unmapped++; - } else { - folio_put(folio); - mpfn =3D 0; - } - -next: - migrate->dst[migrate->npages] =3D 0; - migrate->src[migrate->npages++] =3D mpfn; - } - - /* Only flush the TLB if we actually modified any entries */ - if (unmapped) - flush_tlb_range(walk->vma, start, end); - - lazy_mmu_mode_disable(); - pte_unmap_unlock(ptep - 1, ptl); - - return 0; -} - -static const struct mm_walk_ops migrate_vma_walk_ops =3D { - .pmd_entry =3D migrate_vma_collect_pmd, - .pte_hole =3D migrate_vma_collect_hole, - .walk_lock =3D PGWALK_RDLOCK, -}; - -/* - * migrate_vma_collect() - collect pages over a range of virtual addresses - * @migrate: migrate struct containing all migration information - * - * This will walk the CPU page table. For each virtual address backed by a - * valid page, it updates the src array and takes a reference on the page,= in - * order to pin the page until we lock it and unmap it. - */ -static void migrate_vma_collect(struct migrate_vma *migrate) -{ - struct mmu_notifier_range range; - - /* - * Note that the pgmap_owner is passed to the mmu notifier callback so - * that the registered device driver can skip invalidating device - * private page mappings that won't be migrated. - */ - mmu_notifier_range_init_owner(&range, MMU_NOTIFY_MIGRATE, 0, - migrate->vma->vm_mm, migrate->start, migrate->end, - migrate->pgmap_owner); - mmu_notifier_invalidate_range_start(&range); - - walk_page_range(migrate->vma->vm_mm, migrate->start, migrate->end, - &migrate_vma_walk_ops, migrate); - - mmu_notifier_invalidate_range_end(&range); - migrate->end =3D migrate->start + (migrate->npages << PAGE_SHIFT); -} - /* * migrate_vma_check_page() - check if page is pinned or not * @page: struct page to check @@ -734,7 +226,17 @@ static void migrate_vma_unmap(struct migrate_vma *migr= ate) */ int migrate_vma_setup(struct migrate_vma *args) { + int ret; long nr_pages =3D (args->end - args->start) >> PAGE_SHIFT; + struct hmm_range range =3D { + .notifier =3D NULL, + .start =3D args->start, + .end =3D args->end, + .hmm_pfns =3D args->src, + .dev_private_owner =3D args->pgmap_owner, + .migrate =3D args, + .default_flags =3D HMM_PFN_REQ_MIGRATE + }; =20 args->start &=3D PAGE_MASK; args->end &=3D PAGE_MASK; @@ -759,17 +261,25 @@ int migrate_vma_setup(struct migrate_vma *args) args->cpages =3D 0; args->npages =3D 0; =20 - migrate_vma_collect(args); + if (args->flags & MIGRATE_VMA_FAULT) + range.default_flags |=3D HMM_PFN_REQ_FAULT; + + ret =3D hmm_range_fault(&range); =20 - if (args->cpages) - migrate_vma_unmap(args); + migrate_hmm_range_setup(&range); + + /* Remove migration PTEs */ + if (ret) { + migrate_vma_pages(args); + migrate_vma_finalize(args); + } =20 /* * At this point pages are locked and unmapped, and thus they have * stable content and can safely be copied to destination memory that * is allocated by the drivers. */ - return 0; 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[85.23.51.1]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5a3eee865e7sm3040666e87.10.2026.04.13.21.13.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 13 Apr 2026 21:13:30 -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 , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Marco Pagani Subject: [PATCH v8 5/5] lib/test_hmm:: add a new testcase for the migrate on fault Date: Tue, 14 Apr 2026 07:12:26 +0300 Message-ID: <20260414041226.1539439-6-mpenttil@redhat.com> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20260414041226.1539439-1-mpenttil@redhat.com> References: <20260414041226.1539439-1-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 Enhance the hmm test driver (lib/test_hmm) with migrate on fault case. Cc: David Hildenbrand Cc: Jason Gunthorpe Cc: Leon Romanovsky Cc: Alistair Popple Cc: Balbir Singh Cc: Zi Yan Cc: Matthew Brost Signed-off-by: Marco Pagani Signed-off-by: Mika Penttil=C3=A4 --- lib/test_hmm.c | 99 ++++++++++++++++++++++++++ lib/test_hmm_uapi.h | 19 ++--- tools/testing/selftests/mm/hmm-tests.c | 54 ++++++++++++++ 3 files changed, 163 insertions(+), 9 deletions(-) diff --git a/lib/test_hmm.c b/lib/test_hmm.c index 01aa0b60df2f..5ddcec056dfb 100644 --- a/lib/test_hmm.c +++ b/lib/test_hmm.c @@ -36,6 +36,7 @@ #define DMIRROR_RANGE_FAULT_TIMEOUT 1000 #define DEVMEM_CHUNK_SIZE (256 * 1024 * 1024U) #define DEVMEM_CHUNKS_RESERVE 16 +#define PFNS_ARRAY_SIZE 64 =20 /* * For device_private pages, dpage is just a dummy struct page @@ -1196,6 +1197,100 @@ static int dmirror_migrate_to_device(struct dmirror= *dmirror, return ret; } =20 +static int do_fault_and_migrate(struct dmirror *dmirror, struct hmm_range = *range) +{ + struct migrate_vma *migrate =3D range->migrate; + int ret; + + mmap_read_lock(dmirror->notifier.mm); + + /* Fault-in pages for migration and update device page table */ + ret =3D dmirror_range_fault(dmirror, range); + + pr_debug("Migrating from sys mem to device mem\n"); + migrate_hmm_range_setup(range); + + dmirror_migrate_alloc_and_copy(migrate, dmirror); + migrate_vma_pages(migrate); + dmirror_migrate_finalize_and_map(migrate, dmirror); + migrate_vma_finalize(migrate); + + mmap_read_unlock(dmirror->notifier.mm); + return ret; +} + +static int dmirror_fault_and_migrate_to_device(struct dmirror *dmirror, + struct hmm_dmirror_cmd *cmd) +{ + unsigned long start, size, end, next; + unsigned long src_pfns[PFNS_ARRAY_SIZE] =3D { 0 }; + unsigned long dst_pfns[PFNS_ARRAY_SIZE] =3D { 0 }; + struct migrate_vma migrate =3D { 0 }; + struct hmm_range range =3D { 0 }; + struct dmirror_bounce bounce; + int ret =3D 0; + + /* Whole range */ + start =3D cmd->addr; + size =3D cmd->npages << PAGE_SHIFT; + end =3D start + size; + + if (!mmget_not_zero(dmirror->notifier.mm)) { + ret =3D -EFAULT; + goto out; + } + + migrate.pgmap_owner =3D dmirror->mdevice; + migrate.src =3D src_pfns; + migrate.dst =3D dst_pfns; + migrate.flags =3D MIGRATE_VMA_SELECT_SYSTEM; + + range.migrate =3D &migrate; + range.hmm_pfns =3D src_pfns; + range.pfn_flags_mask =3D 0; + range.default_flags =3D HMM_PFN_REQ_FAULT | HMM_PFN_REQ_MIGRATE; + range.dev_private_owner =3D dmirror->mdevice; + range.notifier =3D &dmirror->notifier; + + for (next =3D start; next < end; next =3D range.end) { + range.start =3D next; + range.end =3D min(end, next + (PFNS_ARRAY_SIZE << PAGE_SHIFT)); + + pr_debug("Fault and migrate range start:%#lx end:%#lx\n", + range.start, range.end); + + ret =3D do_fault_and_migrate(dmirror, &range); + if (ret) + goto out_mmput; + } + + /* + * Return the migrated data for verification. + * Only for pages in device zone + */ + ret =3D dmirror_bounce_init(&bounce, start, size); + if (ret) + goto out_mmput; + + mutex_lock(&dmirror->mutex); + ret =3D dmirror_do_read(dmirror, start, end, &bounce); + mutex_unlock(&dmirror->mutex); + if (ret =3D=3D 0) { + ret =3D copy_to_user(u64_to_user_ptr(cmd->ptr), bounce.ptr, bounce.size); + if (ret) + ret =3D -EFAULT; + } + + cmd->cpages =3D bounce.cpages; + dmirror_bounce_fini(&bounce); + + +out_mmput: + mmput(dmirror->notifier.mm); +out: + return ret; +} + static void dmirror_mkentry(struct dmirror *dmirror, struct hmm_range *ran= ge, unsigned char *perm, unsigned long entry) { @@ -1512,6 +1607,10 @@ static long dmirror_fops_unlocked_ioctl(struct file = *filp, ret =3D dmirror_migrate_to_device(dmirror, &cmd); break; =20 + case HMM_DMIRROR_MIGRATE_ON_FAULT_TO_DEV: + ret =3D dmirror_fault_and_migrate_to_device(dmirror, &cmd); + break; + case HMM_DMIRROR_MIGRATE_TO_SYS: ret =3D dmirror_migrate_to_system(dmirror, &cmd); break; diff --git a/lib/test_hmm_uapi.h b/lib/test_hmm_uapi.h index f94c6d457338..0b6e7a419e36 100644 --- a/lib/test_hmm_uapi.h +++ b/lib/test_hmm_uapi.h @@ -29,15 +29,16 @@ struct hmm_dmirror_cmd { }; =20 /* Expose the address space of the calling process through hmm device file= */ -#define HMM_DMIRROR_READ _IOWR('H', 0x00, struct hmm_dmirror_cmd) -#define HMM_DMIRROR_WRITE _IOWR('H', 0x01, struct hmm_dmirror_cmd) -#define HMM_DMIRROR_MIGRATE_TO_DEV _IOWR('H', 0x02, struct hmm_dmirror_cmd) -#define HMM_DMIRROR_MIGRATE_TO_SYS _IOWR('H', 0x03, struct hmm_dmirror_cmd) -#define HMM_DMIRROR_SNAPSHOT _IOWR('H', 0x04, struct hmm_dmirror_cmd) -#define HMM_DMIRROR_EXCLUSIVE _IOWR('H', 0x05, struct hmm_dmirror_cmd) -#define HMM_DMIRROR_CHECK_EXCLUSIVE _IOWR('H', 0x06, struct hmm_dmirror_cm= d) -#define HMM_DMIRROR_RELEASE _IOWR('H', 0x07, struct hmm_dmirror_cmd) -#define HMM_DMIRROR_FLAGS _IOWR('H', 0x08, struct hmm_dmirror_cmd) +#define HMM_DMIRROR_READ _IOWR('H', 0x00, struct hmm_dmirror_cmd) +#define HMM_DMIRROR_WRITE _IOWR('H', 0x01, struct hmm_dmirror_cmd) +#define HMM_DMIRROR_MIGRATE_TO_DEV _IOWR('H', 0x02, struct hmm_dmirror_cm= d) +#define HMM_DMIRROR_MIGRATE_ON_FAULT_TO_DEV _IOWR('H', 0x03, struct hmm_dm= irror_cmd) +#define HMM_DMIRROR_MIGRATE_TO_SYS _IOWR('H', 0x04, struct hmm_dmirror_cm= d) +#define HMM_DMIRROR_SNAPSHOT _IOWR('H', 0x05, struct hmm_dmirror_cmd) +#define HMM_DMIRROR_EXCLUSIVE _IOWR('H', 0x06, struct hmm_dmirror_cmd) +#define HMM_DMIRROR_CHECK_EXCLUSIVE _IOWR('H', 0x07, struct hmm_dmirror_c= md) +#define HMM_DMIRROR_RELEASE _IOWR('H', 0x08, struct hmm_dmirror_cmd) +#define HMM_DMIRROR_FLAGS _IOWR('H', 0x09, struct hmm_dmirror_cmd) =20 #define HMM_DMIRROR_FLAG_FAIL_ALLOC (1ULL << 0) =20 diff --git a/tools/testing/selftests/mm/hmm-tests.c b/tools/testing/selftes= ts/mm/hmm-tests.c index e8328c89d855..c75616875c9e 100644 --- a/tools/testing/selftests/mm/hmm-tests.c +++ b/tools/testing/selftests/mm/hmm-tests.c @@ -277,6 +277,13 @@ static int hmm_migrate_sys_to_dev(int fd, return hmm_dmirror_cmd(fd, HMM_DMIRROR_MIGRATE_TO_DEV, buffer, npages); } =20 +static int hmm_migrate_on_fault_sys_to_dev(int fd, + struct hmm_buffer *buffer, + unsigned long npages) +{ + return hmm_dmirror_cmd(fd, HMM_DMIRROR_MIGRATE_ON_FAULT_TO_DEV, buffer, n= pages); +} + static int hmm_migrate_dev_to_sys(int fd, struct hmm_buffer *buffer, unsigned long npages) @@ -1034,6 +1041,53 @@ TEST_F(hmm, migrate) hmm_buffer_free(buffer); } =20 + +/* + * Fault and migrate anonymous memory to device private memory. + */ +TEST_F(hmm, migrate_on_fault) +{ + struct hmm_buffer *buffer; + unsigned long npages; + unsigned long size; + unsigned long i; + int *ptr; + int ret; + + npages =3D ALIGN(HMM_BUFFER_SIZE, self->page_size) >> self->page_shift; + ASSERT_NE(npages, 0); + size =3D npages << self->page_shift; + + buffer =3D malloc(sizeof(*buffer)); + ASSERT_NE(buffer, NULL); + + buffer->fd =3D -1; + buffer->size =3D size; + buffer->mirror =3D malloc(size); + ASSERT_NE(buffer->mirror, NULL); + + buffer->ptr =3D mmap(NULL, size, + PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS, + buffer->fd, 0); + ASSERT_NE(buffer->ptr, MAP_FAILED); + + /* Initialize buffer in system memory. */ + for (i =3D 0, ptr =3D buffer->ptr; i < size / sizeof(*ptr); ++i) + ptr[i] =3D i; + + /* Fault and migrate memory to device. */ + ret =3D hmm_migrate_on_fault_sys_to_dev(self->fd, buffer, npages); + ASSERT_EQ(ret, 0); + ASSERT_EQ(buffer->cpages, npages); + + /* Check what the device read. */ + for (i =3D 0, ptr =3D buffer->mirror; i < size / sizeof(*ptr); ++i) + ASSERT_EQ(ptr[i], i); + + hmm_buffer_free(buffer); +} + /* * Migrate anonymous memory to device private memory and fault some of it = back * to system memory, then try migrating the resulting mix of system and de= vice --=20 2.50.0