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Luckily, pagewalk already resolves that for us, so > just have to save it for further use. For migration, mmap_lock > has to be hold for the whole operation, so vma stays stable. > In case lock-drop behavior is requested, return an error while > migrating. Also, rename some struct hmm_vma_walk fields to solve > namespace collisions, and we are later introducing more > xxlocked fields so be unambiguous. > > Take care also of firing the mmu_notifier when migrating. > > Also, prepare for differencies of how mm_struct * is retrieved > in fault and migrate_vma paths. > > 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 > --- > include/linux/migrate.h | 50 +++++++++++++++++- > lib/test_hmm.c | 2 +- > mm/hmm.c | 110 ++++++++++++++++++++++++++++++++++------ > 3 files changed, 145 insertions(+), 17 deletions(-) > > diff --git a/include/linux/migrate.h b/include/linux/migrate.h > index 280ec9a866c7..dd7dd7ec6995 100644 > --- a/include/linux/migrate.h > +++ b/include/linux/migrate.h > @@ -5,6 +5,7 @@ > #include > #include > #include > +#include > #include > #include > > @@ -108,6 +109,29 @@ static inline void softleaf_entry_wait_on_locked(softleaf_t entry, spinlock_t *p > spin_unlock(ptl); > } > > +enum migrate_vma_info { > + MIGRATE_VMA_SELECT_NONE = 0, > + MIGRATE_VMA_SELECT_COMPOUND = MIGRATE_VMA_SELECT_NONE, > +}; > + > +static inline enum migrate_vma_info hmm_select_migrate(struct hmm_range *range) > +{ > + return MIGRATE_VMA_SELECT_NONE; > +} > + > +static inline void hmm_fill_migrate_vma(struct hmm_range *range, > + struct vm_area_struct *vma, > + unsigned long start, > + unsigned long end) > +{ > +} > + > +#ifdef CONFIG_MMU_NOTIFIER > +static inline struct mm_struct *hmm_range_fault_mm(struct hmm_range *range) > +{ > + return range->notifier->mm; > +} > +#endif > #endif /* CONFIG_MIGRATION */ > > #ifdef CONFIG_NUMA_BALANCING > @@ -151,7 +175,8 @@ static inline unsigned long migrate_pfn(unsigned long pfn) > return (pfn << MIGRATE_PFN_SHIFT) | MIGRATE_PFN_VALID; > } > > -enum migrate_vma_direction { > +enum migrate_vma_info { > + MIGRATE_VMA_SELECT_NONE = 0, > MIGRATE_VMA_SELECT_SYSTEM = 1 << 0, > MIGRATE_VMA_SELECT_DEVICE_PRIVATE = 1 << 1, > MIGRATE_VMA_SELECT_DEVICE_COHERENT = 1 << 2, > @@ -193,6 +218,29 @@ struct migrate_vma { > struct page *fault_page; > }; > > +// TODO: enable migration > +static inline enum migrate_vma_info hmm_select_migrate(struct hmm_range *range) > +{ > + return 0; > +} > + > +#ifdef CONFIG_MMU_NOTIFIER > +static inline struct mm_struct *hmm_range_fault_mm(struct hmm_range *range) > +{ > + return range->notifier ? range->notifier->mm : range->migrate->vma->vm_mm; > +} > +#endif > + > +static inline void hmm_fill_migrate_vma(struct hmm_range *range, > + struct vm_area_struct *vma, > + unsigned long start, > + unsigned long end) > +{ > + range->migrate->vma = vma; > + range->migrate->start = start; > + range->migrate->end = end; > +} > + > 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 6911daa9f854..cd88e8177d0a 100644 > --- a/lib/test_hmm.c > +++ b/lib/test_hmm.c > @@ -145,7 +145,7 @@ static bool dmirror_is_private_zone(struct dmirror_device *mdevice) > HMM_DMIRROR_MEMORY_DEVICE_PRIVATE); > } > > -static enum migrate_vma_direction > +static enum migrate_vma_info > dmirror_select_device(struct dmirror *dmirror) > { > return (dmirror->mdevice->zone_device_type == > diff --git a/mm/hmm.c b/mm/hmm.c > index 2f1e98c6b644..4e9542aedc25 100644 > --- a/mm/hmm.c > +++ b/mm/hmm.c > @@ -21,6 +21,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -28,15 +29,23 @@ > #include > #include > #include > +#include > > #include "internal.h" > > struct hmm_vma_walk { > - struct hmm_range *range; > - bool *locked; > - unsigned long last; > - unsigned long end; > - unsigned int required_fault; > + struct mmu_notifier_range mmu_range; > + /* Set once mmu_range is armed with mmu_notifier_invalidate_range_start() */ > + bool mmu_armed; > + struct vm_area_struct *vma; > + struct hmm_range *range; > + unsigned long start; > + unsigned long end; > + unsigned long last; > + /* fault and lock drop related fields */ > + bool *mmlocked; > + unsigned long fault_end; > + unsigned int required_fault; > }; > > /* > @@ -95,7 +104,7 @@ static int hmm_record_fault(unsigned long addr, unsigned long end, > > WARN_ON_ONCE(!required_fault); > hmm_vma_walk->last = addr; > - hmm_vma_walk->end = end; > + hmm_vma_walk->fault_end = end; > hmm_vma_walk->required_fault = required_fault; > return HMM_FAULT_PENDING; > } > @@ -400,6 +409,58 @@ static int hmm_vma_handle_absent_pmd(struct mm_walk *walk, unsigned long start, > } > #endif /* CONFIG_ARCH_HAS_PMD_SOFTLEAVES */ > > +static int hmm_vma_capture_migrate_range(unsigned long start, > + unsigned long end, > + struct mm_walk *walk) > +{ > + struct hmm_vma_walk *hmm_vma_walk = walk->private; > + struct hmm_range *range = hmm_vma_walk->range; > + > + if (!hmm_select_migrate(range)) > + return 0; > + > + if (hmm_vma_walk->vma && (hmm_vma_walk->vma != walk->vma)) > + return -ERANGE; > + > + hmm_vma_walk->vma = walk->vma; I don't quite follow the check for -ERANGE, it checks for hmm_vma_walk->vma != walk->vma, but then set's it later to be the same? > + > + if (end - start > range->end - range->start) > + return -ERANGE; > + Have we established that end > start and same for range->end > range->start? > + if (!hmm_vma_walk->mmu_armed) { > + hmm_vma_walk->start = start; > + hmm_vma_walk->end = end; Does the walk range matter here? > + mmu_notifier_range_init_owner(&hmm_vma_walk->mmu_range, MMU_NOTIFY_MIGRATE, 0, > + walk->vma->vm_mm, start, end, > + range->dev_private_owner); > + mmu_notifier_invalidate_range_start(&hmm_vma_walk->mmu_range); > + hmm_vma_walk->mmu_armed = true; > + } > + > + return 0; > +} > + > +static void hmm_vma_post_range_fault(struct hmm_vma_walk *hmm_vma_walk) > +{ > + > + struct hmm_range *range = hmm_vma_walk->range; > + > + if (hmm_select_migrate(range) && > + hmm_vma_walk->mmu_armed) { > + /* > + * The migrate_vma path has the following initialized, > + * so take care of fault path below. > + */ > + if (range->notifier) { > + hmm_fill_migrate_vma(range, > + hmm_vma_walk->vma, > + hmm_vma_walk->start, > + hmm_vma_walk->end); > + } > + mmu_notifier_invalidate_range_end(&hmm_vma_walk->mmu_range); > + } > +} > + > static int hmm_vma_walk_pmd(pmd_t *pmdp, > unsigned long start, > unsigned long end, > @@ -594,6 +655,11 @@ static int hmm_vma_walk_test(unsigned long start, unsigned long end, > struct hmm_vma_walk *hmm_vma_walk = walk->private; > struct hmm_range *range = hmm_vma_walk->range; > struct vm_area_struct *vma = walk->vma; > + int r; > + > + r = hmm_vma_capture_migrate_range(start, end, walk); > + if (r) > + return r; > > if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)) && > vma->vm_flags & VM_READ) > @@ -646,12 +712,12 @@ static int hmm_do_fault(struct mm_struct *mm, > struct hmm_vma_walk *hmm_vma_walk) > { > unsigned long addr = hmm_vma_walk->last; > - unsigned long end = hmm_vma_walk->end; > + unsigned long end = hmm_vma_walk->fault_end; > unsigned int required_fault = hmm_vma_walk->required_fault; > unsigned int fault_flags = FAULT_FLAG_REMOTE; > struct vm_area_struct *vma; > > - if (hmm_vma_walk->locked) > + if (hmm_vma_walk->mmlocked) > fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; > > vma = vma_lookup(mm, addr); > @@ -670,8 +736,8 @@ static int hmm_do_fault(struct mm_struct *mm, > ret = handle_mm_fault(vma, addr, fault_flags, NULL); > > if (ret & (VM_FAULT_COMPLETED | VM_FAULT_RETRY)) { > - if (hmm_vma_walk->locked) /* needed by sparse */ > - *hmm_vma_walk->locked = false; > + if (hmm_vma_walk->mmlocked) /* needed by sparse */ > + *hmm_vma_walk->mmlocked = false; > else > WARN_ON_ONCE(1); /* broken fault handler */ > return HMM_FAULT_UNLOCKED; > @@ -694,19 +760,31 @@ static int hmm_range_fault_locked(struct hmm_range *range, bool *locked) > { > struct hmm_vma_walk hmm_vma_walk = { > .range = range, > - .locked = locked, > + .mmlocked = locked, > .last = range->start, > }; > - struct mm_struct *mm = range->notifier->mm; > + /* > + * 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). > + * > + */ > + struct mm_struct *mm = hmm_range_fault_mm(range); > int ret; > > + /* Migration is incompatible with mmap lock drop */ > + if (locked && hmm_select_migrate(range)) > + return -EINVAL; > + > mmap_assert_locked(mm); > > do { > /* If range is no longer valid force retry. */ > - if (mmu_interval_check_retry(range->notifier, > - range->notifier_seq)) > - return -EBUSY; > + if (range->notifier && mmu_interval_check_retry(range->notifier, > + range->notifier_seq)) { > + ret = -EBUSY; > + break; > + } > ret = walk_page_range(mm, hmm_vma_walk.last, range->end, > &hmm_walk_ops, &hmm_vma_walk); > /* > @@ -732,6 +810,8 @@ static int hmm_range_fault_locked(struct hmm_range *range, bool *locked) > * output, and all >= are still at their input values. > */ > } while (ret == -EBUSY); > + > + hmm_vma_post_range_fault(&hmm_vma_walk); Have you checked to see if we could end up with notifier start/end inbalance? For example if hmm_select_migrate returns false? > return ret; > } >