diff options
| -rw-r--r-- | include/exec/memory.h | 7 | ||||
| -rw-r--r-- | migration/ram.c | 324 | ||||
| -rw-r--r-- | migration/ram.h | 2 | ||||
| -rw-r--r-- | migration/trace-events | 2 |
4 files changed, 306 insertions, 29 deletions
diff --git a/include/exec/memory.h b/include/exec/memory.h index 3709621..e58c09f 100644 --- a/include/exec/memory.h +++ b/include/exec/memory.h @@ -150,6 +150,13 @@ typedef struct IOMMUTLBEvent { #define RAM_PMEM (1 << 5) +/* + * UFFDIO_WRITEPROTECT is used on this RAMBlock to + * support 'write-tracking' migration type. + * Implies ram_state->ram_wt_enabled. + */ +#define RAM_UF_WRITEPROTECT (1 << 6) + static inline void iommu_notifier_init(IOMMUNotifier *n, IOMMUNotify fn, IOMMUNotifierFlag flags, hwaddr start, hwaddr end, diff --git a/migration/ram.c b/migration/ram.c index ae8de17..26adb55 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -56,6 +56,11 @@ #include "savevm.h" #include "qemu/iov.h" #include "multifd.h" +#include "sysemu/runstate.h" + +#if defined(__linux__) +#include "qemu/userfaultfd.h" +#endif /* defined(__linux__) */ /***********************************************************/ /* ram save/restore */ @@ -298,6 +303,8 @@ struct RAMSrcPageRequest { struct RAMState { /* QEMUFile used for this migration */ QEMUFile *f; + /* UFFD file descriptor, used in 'write-tracking' migration */ + int uffdio_fd; /* Last block that we have visited searching for dirty pages */ RAMBlock *last_seen_block; /* Last block from where we have sent data */ @@ -1434,6 +1441,269 @@ static RAMBlock *unqueue_page(RAMState *rs, ram_addr_t *offset) return block; } +#if defined(__linux__) +/** + * poll_fault_page: try to get next UFFD write fault page and, if pending fault + * is found, return RAM block pointer and page offset + * + * Returns pointer to the RAMBlock containing faulting page, + * NULL if no write faults are pending + * + * @rs: current RAM state + * @offset: page offset from the beginning of the block + */ +static RAMBlock *poll_fault_page(RAMState *rs, ram_addr_t *offset) +{ + struct uffd_msg uffd_msg; + void *page_address; + RAMBlock *bs; + int res; + + if (!migrate_background_snapshot()) { + return NULL; + } + + res = uffd_read_events(rs->uffdio_fd, &uffd_msg, 1); + if (res <= 0) { + return NULL; + } + + page_address = (void *)(uintptr_t) uffd_msg.arg.pagefault.address; + bs = qemu_ram_block_from_host(page_address, false, offset); + assert(bs && (bs->flags & RAM_UF_WRITEPROTECT) != 0); + return bs; +} + +/** + * ram_save_release_protection: release UFFD write protection after + * a range of pages has been saved + * + * @rs: current RAM state + * @pss: page-search-status structure + * @start_page: index of the first page in the range relative to pss->block + * + * Returns 0 on success, negative value in case of an error +*/ +static int ram_save_release_protection(RAMState *rs, PageSearchStatus *pss, + unsigned long start_page) +{ + int res = 0; + + /* Check if page is from UFFD-managed region. */ + if (pss->block->flags & RAM_UF_WRITEPROTECT) { + void *page_address = pss->block->host + (start_page << TARGET_PAGE_BITS); + uint64_t run_length = (pss->page - start_page + 1) << TARGET_PAGE_BITS; + + /* Flush async buffers before un-protect. */ + qemu_fflush(rs->f); + /* Un-protect memory range. */ + res = uffd_change_protection(rs->uffdio_fd, page_address, run_length, + false, false); + } + + return res; +} + +/* ram_write_tracking_available: check if kernel supports required UFFD features + * + * Returns true if supports, false otherwise + */ +bool ram_write_tracking_available(void) +{ + uint64_t uffd_features; + int res; + + res = uffd_query_features(&uffd_features); + return (res == 0 && + (uffd_features & UFFD_FEATURE_PAGEFAULT_FLAG_WP) != 0); +} + +/* ram_write_tracking_compatible: check if guest configuration is + * compatible with 'write-tracking' + * + * Returns true if compatible, false otherwise + */ +bool ram_write_tracking_compatible(void) +{ + const uint64_t uffd_ioctls_mask = BIT(_UFFDIO_WRITEPROTECT); + int uffd_fd; + RAMBlock *bs; + bool ret = false; + + /* Open UFFD file descriptor */ + uffd_fd = uffd_create_fd(UFFD_FEATURE_PAGEFAULT_FLAG_WP, false); + if (uffd_fd < 0) { + return false; + } + + RCU_READ_LOCK_GUARD(); + + RAMBLOCK_FOREACH_NOT_IGNORED(bs) { + uint64_t uffd_ioctls; + + /* Nothing to do with read-only and MMIO-writable regions */ + if (bs->mr->readonly || bs->mr->rom_device) { + continue; + } + /* Try to register block memory via UFFD-IO to track writes */ + if (uffd_register_memory(uffd_fd, bs->host, bs->max_length, + UFFDIO_REGISTER_MODE_WP, &uffd_ioctls)) { + goto out; + } + if ((uffd_ioctls & uffd_ioctls_mask) != uffd_ioctls_mask) { + goto out; + } + } + ret = true; + +out: + uffd_close_fd(uffd_fd); + return ret; +} + +/* + * ram_write_tracking_start: start UFFD-WP memory tracking + * + * Returns 0 for success or negative value in case of error + */ +int ram_write_tracking_start(void) +{ + int uffd_fd; + RAMState *rs = ram_state; + RAMBlock *bs; + + /* Open UFFD file descriptor */ + uffd_fd = uffd_create_fd(UFFD_FEATURE_PAGEFAULT_FLAG_WP, true); + if (uffd_fd < 0) { + return uffd_fd; + } + rs->uffdio_fd = uffd_fd; + + RCU_READ_LOCK_GUARD(); + + RAMBLOCK_FOREACH_NOT_IGNORED(bs) { + /* Nothing to do with read-only and MMIO-writable regions */ + if (bs->mr->readonly || bs->mr->rom_device) { + continue; + } + + /* Register block memory with UFFD to track writes */ + if (uffd_register_memory(rs->uffdio_fd, bs->host, + bs->max_length, UFFDIO_REGISTER_MODE_WP, NULL)) { + goto fail; + } + /* Apply UFFD write protection to the block memory range */ + if (uffd_change_protection(rs->uffdio_fd, bs->host, + bs->max_length, true, false)) { + goto fail; + } + bs->flags |= RAM_UF_WRITEPROTECT; + memory_region_ref(bs->mr); + + trace_ram_write_tracking_ramblock_start(bs->idstr, bs->page_size, + bs->host, bs->max_length); + } + + return 0; + +fail: + error_report("ram_write_tracking_start() failed: restoring initial memory state"); + + RAMBLOCK_FOREACH_NOT_IGNORED(bs) { + if ((bs->flags & RAM_UF_WRITEPROTECT) == 0) { + continue; + } + /* + * In case some memory block failed to be write-protected + * remove protection and unregister all succeeded RAM blocks + */ + uffd_change_protection(rs->uffdio_fd, bs->host, bs->max_length, false, false); + uffd_unregister_memory(rs->uffdio_fd, bs->host, bs->max_length); + /* Cleanup flags and remove reference */ + bs->flags &= ~RAM_UF_WRITEPROTECT; + memory_region_unref(bs->mr); + } + + uffd_close_fd(uffd_fd); + rs->uffdio_fd = -1; + return -1; +} + +/** + * ram_write_tracking_stop: stop UFFD-WP memory tracking and remove protection + */ +void ram_write_tracking_stop(void) +{ + RAMState *rs = ram_state; + RAMBlock *bs; + + RCU_READ_LOCK_GUARD(); + + RAMBLOCK_FOREACH_NOT_IGNORED(bs) { + if ((bs->flags & RAM_UF_WRITEPROTECT) == 0) { + continue; + } + /* Remove protection and unregister all affected RAM blocks */ + uffd_change_protection(rs->uffdio_fd, bs->host, bs->max_length, false, false); + uffd_unregister_memory(rs->uffdio_fd, bs->host, bs->max_length); + + trace_ram_write_tracking_ramblock_stop(bs->idstr, bs->page_size, + bs->host, bs->max_length); + + /* Cleanup flags and remove reference */ + bs->flags &= ~RAM_UF_WRITEPROTECT; + memory_region_unref(bs->mr); + } + + /* Finally close UFFD file descriptor */ + uffd_close_fd(rs->uffdio_fd); + rs->uffdio_fd = -1; +} + +#else +/* No target OS support, stubs just fail or ignore */ + +static RAMBlock *poll_fault_page(RAMState *rs, ram_addr_t *offset) +{ + (void) rs; + (void) offset; + + return NULL; +} + +static int ram_save_release_protection(RAMState *rs, PageSearchStatus *pss, + unsigned long start_page) +{ + (void) rs; + (void) pss; + (void) start_page; + + return 0; +} + +bool ram_write_tracking_available(void) +{ + return false; +} + +bool ram_write_tracking_compatible(void) +{ + assert(0); + return false; +} + +int ram_write_tracking_start(void) +{ + assert(0); + return -1; +} + +void ram_write_tracking_stop(void) +{ + assert(0); +} +#endif /* defined(__linux__) */ + /** * get_queued_page: unqueue a page from the postcopy requests * @@ -1473,6 +1743,14 @@ static bool get_queued_page(RAMState *rs, PageSearchStatus *pss) } while (block && !dirty); + if (!block) { + /* + * Poll write faults too if background snapshot is enabled; that's + * when we have vcpus got blocked by the write protected pages. + */ + block = poll_fault_page(rs, &offset); + } + if (block) { /* * As soon as we start servicing pages out of order, then we have @@ -1715,6 +1993,8 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss, int tmppages, pages = 0; size_t pagesize_bits = qemu_ram_pagesize(pss->block) >> TARGET_PAGE_BITS; + unsigned long start_page = pss->page; + int res; if (ramblock_is_ignored(pss->block)) { error_report("block %s should not be migrated !", pss->block->idstr); @@ -1740,10 +2020,11 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss, } while ((pss->page & (pagesize_bits - 1)) && offset_in_ramblock(pss->block, ((ram_addr_t)pss->page) << TARGET_PAGE_BITS)); - /* The offset we leave with is the last one we looked at */ pss->page--; - return pages; + + res = ram_save_release_protection(rs, pss, start_page); + return (res < 0 ? res : pages); } /** @@ -1880,10 +2161,13 @@ static void ram_save_cleanup(void *opaque) RAMState **rsp = opaque; RAMBlock *block; - /* caller have hold iothread lock or is in a bh, so there is - * no writing race against the migration bitmap - */ - memory_global_dirty_log_stop(); + /* We don't use dirty log with background snapshots */ + if (!migrate_background_snapshot()) { + /* caller have hold iothread lock or is in a bh, so there is + * no writing race against the migration bitmap + */ + memory_global_dirty_log_stop(); + } RAMBLOCK_FOREACH_NOT_IGNORED(block) { g_free(block->clear_bmap); @@ -2343,8 +2627,11 @@ static void ram_init_bitmaps(RAMState *rs) WITH_RCU_READ_LOCK_GUARD() { ram_list_init_bitmaps(); - memory_global_dirty_log_start(); - migration_bitmap_sync_precopy(rs); + /* We don't use dirty log with background snapshots */ + if (!migrate_background_snapshot()) { + memory_global_dirty_log_start(); + migration_bitmap_sync_precopy(rs); + } } qemu_mutex_unlock_ramlist(); qemu_mutex_unlock_iothread(); @@ -3788,27 +4075,6 @@ static int ram_resume_prepare(MigrationState *s, void *opaque) return 0; } -/* ram_write_tracking_available: check if kernel supports required UFFD features - * - * Returns true if supports, false otherwise - */ -bool ram_write_tracking_available(void) -{ - /* TODO: implement */ - return false; -} - -/* ram_write_tracking_compatible: check if guest configuration is - * compatible with 'write-tracking' - * - * Returns true if compatible, false otherwise - */ -bool ram_write_tracking_compatible(void) -{ - /* TODO: implement */ - return false; -} - static SaveVMHandlers savevm_ram_handlers = { .save_setup = ram_save_setup, .save_live_iterate = ram_save_iterate, diff --git a/migration/ram.h b/migration/ram.h index 1a9ff90..c25540c 100644 --- a/migration/ram.h +++ b/migration/ram.h @@ -82,5 +82,7 @@ void colo_incoming_start_dirty_log(void); /* Background snapshot */ bool ram_write_tracking_available(void); bool ram_write_tracking_compatible(void); +int ram_write_tracking_start(void); +void ram_write_tracking_stop(void); #endif diff --git a/migration/trace-events b/migration/trace-events index 75de500..668c562 100644 --- a/migration/trace-events +++ b/migration/trace-events @@ -111,6 +111,8 @@ save_xbzrle_page_skipping(void) "" save_xbzrle_page_overflow(void) "" ram_save_iterate_big_wait(uint64_t milliconds, int iterations) "big wait: %" PRIu64 " milliseconds, %d iterations" ram_load_complete(int ret, uint64_t seq_iter) "exit_code %d seq iteration %" PRIu64 +ram_write_tracking_ramblock_start(const char *block_id, size_t page_size, void *addr, size_t length) "%s: page_size: %zu addr: %p length: %zu" +ram_write_tracking_ramblock_stop(const char *block_id, size_t page_size, void *addr, size_t length) "%s: page_size: %zu addr: %p length: %zu" # multifd.c multifd_new_send_channel_async(uint8_t id) "channel %d" |