diff options
Diffstat (limited to 'migration/ram.c')
| -rw-r--r-- | migration/ram.c | 181 |
1 files changed, 180 insertions, 1 deletions
diff --git a/migration/ram.c b/migration/ram.c index c703176c74..b481d555e9 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -32,6 +32,7 @@ #include "qemu/timer.h" #include "qemu/main-loop.h" #include "migration/migration.h" +#include "migration/postcopy-ram.h" #include "exec/address-spaces.h" #include "migration/page_cache.h" #include "qemu/error-report.h" @@ -967,6 +968,8 @@ static int ram_save_compressed_page(QEMUFile *f, RAMBlock *block, * @f: Current migration stream. * @pss: Data about the state of the current dirty page scan. * @*again: Set to false if the search has scanned the whole of RAM + * *ram_addr_abs: Pointer into which to store the address of the dirty page + * within the global ram_addr space */ static bool find_dirty_block(QEMUFile *f, PageSearchStatus *pss, bool *again, ram_addr_t *ram_addr_abs) @@ -1064,7 +1067,6 @@ static int ram_find_and_save_block(QEMUFile *f, bool last_stage, if (unsentmap) { clear_bit(dirty_ram_abs >> TARGET_PAGE_BITS, unsentmap); } - } } } while (!pages && again); @@ -1233,6 +1235,183 @@ void ram_debug_dump_bitmap(unsigned long *todump, bool expected) } } +/* **** functions for postcopy ***** */ + +/* + * Callback from postcopy_each_ram_send_discard for each RAMBlock + * Note: At this point the 'unsentmap' is the processed bitmap combined + * with the dirtymap; so a '1' means it's either dirty or unsent. + * start,length: Indexes into the bitmap for the first bit + * representing the named block and length in target-pages + */ +static int postcopy_send_discard_bm_ram(MigrationState *ms, + PostcopyDiscardState *pds, + unsigned long start, + unsigned long length) +{ + unsigned long end = start + length; /* one after the end */ + unsigned long current; + unsigned long *unsentmap; + + unsentmap = atomic_rcu_read(&migration_bitmap_rcu)->unsentmap; + for (current = start; current < end; ) { + unsigned long one = find_next_bit(unsentmap, end, current); + + if (one <= end) { + unsigned long zero = find_next_zero_bit(unsentmap, end, one + 1); + unsigned long discard_length; + + if (zero >= end) { + discard_length = end - one; + } else { + discard_length = zero - one; + } + postcopy_discard_send_range(ms, pds, one, discard_length); + current = one + discard_length; + } else { + current = one; + } + } + + return 0; +} + +/* + * Utility for the outgoing postcopy code. + * Calls postcopy_send_discard_bm_ram for each RAMBlock + * passing it bitmap indexes and name. + * Returns: 0 on success + * (qemu_ram_foreach_block ends up passing unscaled lengths + * which would mean postcopy code would have to deal with target page) + */ +static int postcopy_each_ram_send_discard(MigrationState *ms) +{ + struct RAMBlock *block; + int ret; + + QLIST_FOREACH_RCU(block, &ram_list.blocks, next) { + unsigned long first = block->offset >> TARGET_PAGE_BITS; + PostcopyDiscardState *pds = postcopy_discard_send_init(ms, + first, + block->idstr); + + /* + * Postcopy sends chunks of bitmap over the wire, but it + * just needs indexes at this point, avoids it having + * target page specific code. + */ + ret = postcopy_send_discard_bm_ram(ms, pds, first, + block->used_length >> TARGET_PAGE_BITS); + postcopy_discard_send_finish(ms, pds); + if (ret) { + return ret; + } + } + + return 0; +} + +/* + * Transmit the set of pages to be discarded after precopy to the target + * these are pages that: + * a) Have been previously transmitted but are now dirty again + * b) Pages that have never been transmitted, this ensures that + * any pages on the destination that have been mapped by background + * tasks get discarded (transparent huge pages is the specific concern) + * Hopefully this is pretty sparse + */ +int ram_postcopy_send_discard_bitmap(MigrationState *ms) +{ + int ret; + unsigned long *bitmap, *unsentmap; + + rcu_read_lock(); + + /* This should be our last sync, the src is now paused */ + migration_bitmap_sync(); + + unsentmap = atomic_rcu_read(&migration_bitmap_rcu)->unsentmap; + if (!unsentmap) { + /* We don't have a safe way to resize the sentmap, so + * if the bitmap was resized it will be NULL at this + * point. + */ + error_report("migration ram resized during precopy phase"); + rcu_read_unlock(); + return -EINVAL; + } + + /* + * Update the unsentmap to be unsentmap = unsentmap | dirty + */ + bitmap = atomic_rcu_read(&migration_bitmap_rcu)->bmap; + bitmap_or(unsentmap, unsentmap, bitmap, + last_ram_offset() >> TARGET_PAGE_BITS); + + + trace_ram_postcopy_send_discard_bitmap(); +#ifdef DEBUG_POSTCOPY + ram_debug_dump_bitmap(unsentmap, true); +#endif + + ret = postcopy_each_ram_send_discard(ms); + rcu_read_unlock(); + + return ret; +} + +/* + * At the start of the postcopy phase of migration, any now-dirty + * precopied pages are discarded. + * + * start, length describe a byte address range within the RAMBlock + * + * Returns 0 on success. + */ +int ram_discard_range(MigrationIncomingState *mis, + const char *block_name, + uint64_t start, size_t length) +{ + int ret = -1; + + rcu_read_lock(); + RAMBlock *rb = qemu_ram_block_by_name(block_name); + + if (!rb) { + error_report("ram_discard_range: Failed to find block '%s'", + block_name); + goto err; + } + + uint8_t *host_startaddr = rb->host + start; + + if ((uintptr_t)host_startaddr & (qemu_host_page_size - 1)) { + error_report("ram_discard_range: Unaligned start address: %p", + host_startaddr); + goto err; + } + + if ((start + length) <= rb->used_length) { + uint8_t *host_endaddr = host_startaddr + length; + if ((uintptr_t)host_endaddr & (qemu_host_page_size - 1)) { + error_report("ram_discard_range: Unaligned end address: %p", + host_endaddr); + goto err; + } + ret = postcopy_ram_discard_range(mis, host_startaddr, length); + } else { + error_report("ram_discard_range: Overrun block '%s' (%" PRIu64 + "/%zu/%zu)", + block_name, start, length, rb->used_length); + } + +err: + rcu_read_unlock(); + + return ret; +} + + /* Each of ram_save_setup, ram_save_iterate and ram_save_complete has * long-running RCU critical section. When rcu-reclaims in the code * start to become numerous it will be necessary to reduce the |