Messages in this thread | | | Subject | Re: [PATCH v2 3/5] mm/notifier: add migration invalidation type | From | Ralph Campbell <> | Date | Mon, 20 Jul 2020 12:56:31 -0700 |
| |
On 7/20/20 11:40 AM, Jason Gunthorpe wrote: > On Mon, Jul 13, 2020 at 10:21:47AM -0700, Ralph Campbell wrote: >> Currently migrate_vma_setup() calls mmu_notifier_invalidate_range_start() >> which flushes all device private page mappings whether or not a page >> is being migrated to/from device private memory. In order to not disrupt >> device mappings that are not being migrated, shift the responsibility >> for clearing device private mappings to the device driver and leave >> CPU page table unmapping handled by migrate_vma_setup(). To support >> this, the caller of migrate_vma_setup() should always set struct >> migrate_vma::src_owner to a non NULL value that matches the device >> private page->pgmap->owner. This value is then passed to the struct >> mmu_notifier_range with a new event type which the driver's invalidation >> function can use to avoid device MMU invalidations. >> >> Signed-off-by: Ralph Campbell <rcampbell@nvidia.com> >> include/linux/mmu_notifier.h | 7 +++++++ >> mm/migrate.c | 8 +++++++- >> 2 files changed, 14 insertions(+), 1 deletion(-) >> >> diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h >> index fc68f3570e19..1921fcf6be5b 100644 >> +++ b/include/linux/mmu_notifier.h >> @@ -38,6 +38,10 @@ struct mmu_interval_notifier; >> * >> * @MMU_NOTIFY_RELEASE: used during mmu_interval_notifier invalidate to signal >> * that the mm refcount is zero and the range is no longer accessible. >> + * >> + * @MMU_NOTIFY_MIGRATE: used during migrate_vma_collect() invalidate to signal >> + * a device driver to possibly ignore the invalidation if the >> + * migrate_pgmap_owner field matches the driver's device private pgmap owner. >> */ >> enum mmu_notifier_event { >> MMU_NOTIFY_UNMAP = 0, >> @@ -46,6 +50,7 @@ enum mmu_notifier_event { >> MMU_NOTIFY_PROTECTION_PAGE, >> MMU_NOTIFY_SOFT_DIRTY, >> MMU_NOTIFY_RELEASE, >> + MMU_NOTIFY_MIGRATE, >> }; >> >> #define MMU_NOTIFIER_RANGE_BLOCKABLE (1 << 0) >> @@ -264,6 +269,7 @@ struct mmu_notifier_range { >> unsigned long end; >> unsigned flags; >> enum mmu_notifier_event event; >> + void *migrate_pgmap_owner; >> }; >> >> static inline int mm_has_notifiers(struct mm_struct *mm) >> @@ -513,6 +519,7 @@ static inline void mmu_notifier_range_init(struct mmu_notifier_range *range, >> range->start = start; >> range->end = end; >> range->flags = flags; >> + range->migrate_pgmap_owner = NULL; >> } >> >> #define ptep_clear_flush_young_notify(__vma, __address, __ptep) \ >> diff --git a/mm/migrate.c b/mm/migrate.c >> index 2bbc5c4c672e..9b3dcb81be5f 100644 >> +++ b/mm/migrate.c >> @@ -2391,8 +2391,14 @@ static void migrate_vma_collect(struct migrate_vma *migrate) >> { >> struct mmu_notifier_range range; >> >> - mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, NULL, >> + /* >> + * Note that the src_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(&range, MMU_NOTIFY_MIGRATE, 0, migrate->vma, >> migrate->vma->vm_mm, migrate->start, migrate->end); > > So the idea is that src_owner is always set to the pgmap owner when > working with DEVICE_PRIVATE? > > But then the comment in the prior patch should be fixed: > > @@ -199,11 +204,12 @@ struct migrate_vma { > > /* > * Set to the owner value also stored in page->pgmap->owner for > + * migrating device private memory. The direction also needs to > + * be set to MIGRATE_VMA_FROM_DEVICE_PRIVATE. > > To say the caller must always provide src_owner. > > And that field should probably be renamed at this point, as there is > nothing "src" about it. It is just the pgmap_owner of the > DEVICE_PRIVATE pages the TO/FROM DEVICE migration is working on. > > Jason
Good point. I'll send a v3 with your suggested changes.
| |