diff options
| -rw-r--r-- | migration/ram.c | 77 |
1 files changed, 77 insertions, 0 deletions
diff --git a/migration/ram.c b/migration/ram.c index ae2601bf3b..e8c06f207c 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -858,6 +858,60 @@ static inline bool migration_bitmap_clear_dirty(RAMState *rs, return ret; } +static void dirty_bitmap_clear_section(MemoryRegionSection *section, + void *opaque) +{ + const hwaddr offset = section->offset_within_region; + const hwaddr size = int128_get64(section->size); + const unsigned long start = offset >> TARGET_PAGE_BITS; + const unsigned long npages = size >> TARGET_PAGE_BITS; + RAMBlock *rb = section->mr->ram_block; + uint64_t *cleared_bits = opaque; + + /* + * We don't grab ram_state->bitmap_mutex because we expect to run + * only when starting migration or during postcopy recovery where + * we don't have concurrent access. + */ + if (!migration_in_postcopy() && !migrate_background_snapshot()) { + migration_clear_memory_region_dirty_bitmap_range(rb, start, npages); + } + *cleared_bits += bitmap_count_one_with_offset(rb->bmap, start, npages); + bitmap_clear(rb->bmap, start, npages); +} + +/* + * Exclude all dirty pages from migration that fall into a discarded range as + * managed by a RamDiscardManager responsible for the mapped memory region of + * the RAMBlock. Clear the corresponding bits in the dirty bitmaps. + * + * Discarded pages ("logically unplugged") have undefined content and must + * not get migrated, because even reading these pages for migration might + * result in undesired behavior. + * + * Returns the number of cleared bits in the RAMBlock dirty bitmap. + * + * Note: The result is only stable while migrating (precopy/postcopy). + */ +static uint64_t ramblock_dirty_bitmap_clear_discarded_pages(RAMBlock *rb) +{ + uint64_t cleared_bits = 0; + + if (rb->mr && rb->bmap && memory_region_has_ram_discard_manager(rb->mr)) { + RamDiscardManager *rdm = memory_region_get_ram_discard_manager(rb->mr); + MemoryRegionSection section = { + .mr = rb->mr, + .offset_within_region = 0, + .size = int128_make64(qemu_ram_get_used_length(rb)), + }; + + ram_discard_manager_replay_discarded(rdm, §ion, + dirty_bitmap_clear_section, + &cleared_bits); + } + return cleared_bits; +} + /* Called with RCU critical section */ static void ramblock_sync_dirty_bitmap(RAMState *rs, RAMBlock *rb) { @@ -2675,6 +2729,19 @@ static void ram_list_init_bitmaps(void) } } +static void migration_bitmap_clear_discarded_pages(RAMState *rs) +{ + unsigned long pages; + RAMBlock *rb; + + RCU_READ_LOCK_GUARD(); + + RAMBLOCK_FOREACH_NOT_IGNORED(rb) { + pages = ramblock_dirty_bitmap_clear_discarded_pages(rb); + rs->migration_dirty_pages -= pages; + } +} + static void ram_init_bitmaps(RAMState *rs) { /* For memory_global_dirty_log_start below. */ @@ -2691,6 +2758,12 @@ static void ram_init_bitmaps(RAMState *rs) } qemu_mutex_unlock_ramlist(); qemu_mutex_unlock_iothread(); + + /* + * After an eventual first bitmap sync, fixup the initial bitmap + * containing all 1s to exclude any discarded pages from migration. + */ + migration_bitmap_clear_discarded_pages(rs); } static int ram_init_all(RAMState **rsp) @@ -4119,6 +4192,10 @@ int ram_dirty_bitmap_reload(MigrationState *s, RAMBlock *block) */ bitmap_complement(block->bmap, block->bmap, nbits); + /* Clear dirty bits of discarded ranges that we don't want to migrate. */ + ramblock_dirty_bitmap_clear_discarded_pages(block); + + /* We'll recalculate migration_dirty_pages in ram_state_resume_prepare(). */ trace_ram_dirty_bitmap_reload_complete(block->idstr); /* |