It is likely to crash qemu when resize the xbzrle cache during migration. Because the xbzrle cache will be modified by migration thread and resize thread.
Test scene step one: set the size of xbzrle cache 1GB. step two: migrate vm which dirty memory continuously. step three: set the size of xbzrle cache 0.125GB. Signed-off-by: ChenLiang <chenlian...@huawei.com<mailto:chenlian...@huawei.com>> Signed-off-by: Gonglei <arei.gong...@huawei.com<mailto:arei.gong...@huawei.com>> --- arch_init.c | 42 ++++++++++++++++++++++++++++++++++++--- include/migration/page_cache.h | 14 +++++++++++++ page_cache.c | 13 ++++++++++++ 3 files changed, 65 insertions(+), 4 deletions(-) diff --git a/arch_init.c b/arch_init.c index 80574a0..e2d2c72 100644 --- a/arch_init.c +++ b/arch_init.c @@ -164,26 +164,56 @@ static struct { uint8_t *encoded_buf; /* buffer for storing page content */ uint8_t *current_buf; - /* Cache for XBZRLE */ + /* Cache for XBZRLE, Protected by lock. */ PageCache *cache; + QemuMutex lock; } XBZRLE = { .encoded_buf = NULL, .current_buf = NULL, .cache = NULL, }; + /* buffer used for XBZRLE decoding */ static uint8_t *xbzrle_decoded_buf; +static void XBZRLE_cache_lock(void) +{ + qemu_mutex_lock(&XBZRLE.lock); +} + +static void XBZRLE_cache_unlock(void) +{ + qemu_mutex_unlock(&XBZRLE.lock); +} + + int64_t xbzrle_cache_resize(int64_t new_size) { + PageCache *new_cache, *old_cache; + if (new_size < TARGET_PAGE_SIZE) { return -1; } if (XBZRLE.cache != NULL) { - return cache_resize(XBZRLE.cache, new_size / TARGET_PAGE_SIZE) * - TARGET_PAGE_SIZE; + if (pow2floor(new_size) == cache_max_num_items(XBZRLE.cache) + *TARGET_PAGE_SIZE) { + goto ret; + } + new_cache = cache_init(new_size / TARGET_PAGE_SIZE, + cache_page_size(XBZRLE.cache)); + if (!new_cache) { + DPRINTF("Error creating cache\n"); + return -1; + } + XBZRLE_cache_lock(); + old_cache = XBZRLE.cache; + XBZRLE.cache = new_cache; + XBZRLE_cache_unlock(); + cache_fini(old_cache); + goto ret; } +ret: return pow2floor(new_size); } @@ -522,6 +552,8 @@ static int ram_save_block(QEMUFile *f, bool last_stage) ret = ram_control_save_page(f, block->offset, offset, TARGET_PAGE_SIZE, &bytes_sent); + XBZRLE_cache_lock(); + if (ret != RAM_SAVE_CONTROL_NOT_SUPP) { if (ret != RAM_SAVE_CONTROL_DELAYED) { if (bytes_sent > 0) { @@ -553,6 +585,8 @@ static int ram_save_block(QEMUFile *f, bool last_stage) acct_info.norm_pages++; } + XBZRLE_cache_unlock(); + /* if page is unmodified, continue to the next */ if (bytes_sent > 0) { last_sent_block = block; @@ -681,7 +715,7 @@ static int ram_save_setup(QEMUFile *f, void *opaque) XBZRLE.encoded_buf = NULL; return -1; } - + qemu_mutex_init(&XBZRLE.lock); acct_clear(); } diff --git a/include/migration/page_cache.h b/include/migration/page_cache.h index d156f0d..6be0103 100644 --- a/include/migration/page_cache.h +++ b/include/migration/page_cache.h @@ -79,4 +79,18 @@ int cache_insert(PageCache *cache, uint64_t addr, uint8_t *pdata); */ int64_t cache_resize(PageCache *cache, int64_t num_pages); +/** + * cache_max_num_items: return the cache max num items. + * + * @cache pointer to the PageCache struct + */ +int64_t cache_max_num_items(PageCache *cache); + +/** + * cache_page_size: return the cache page size + * + * @cache pointer to the PageCache struct + */ +unsigned int cache_page_size(PageCache *cache); + #endif diff --git a/page_cache.c b/page_cache.c index 3ef6ee7..92e401c 100644 --- a/page_cache.c +++ b/page_cache.c @@ -234,3 +234,16 @@ int64_t cache_resize(PageCache *cache, int64_t new_num_pages) return cache->max_num_items; } + +int64_t cache_max_num_items(PageCache *cache) +{ + g_assert(cache); + return cache->max_num_items; +} + +unsigned int cache_page_size(PageCache *cache) +{ + g_assert(cache); + return cache->page_size; +} + -- 1.6.0.2 Best regards, -Gonglei
