From: Stefan Reiter Date: Wed, 21 Oct 2020 14:44:56 +0000 (+0200) Subject: migration/block-dirty-bitmap: fix larger granularity bitmaps X-Git-Tag: qemu-xen-4.16.0-rc4~552^2~1 X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=ed7b70c27b5c11ff4800e608d301cd7a36b81c5e;p=qemu-xen.git migration/block-dirty-bitmap: fix larger granularity bitmaps sectors_per_chunk is a 64 bit integer, but the calculation is done in 32 bits, leading to an overflow for coarse bitmap granularities. If that results in the value 0, it leads to a hang where no progress is made but send_bitmap_bits is constantly called with nr_sectors being 0. Signed-off-by: Stefan Reiter Message-Id: <20201021144456.1072-1-s.reiter@proxmox.com> Fixes: b35ebdf07 migration: add postcopy migration of dirty bitmaps Reviewed-by: Vladimir Sementsov-Ogievskiy Reviewed-by: Eric Blake [eblake: Use correct type for 8ULL, use () to avoid overflow] Signed-off-by: Eric Blake --- diff --git a/migration/block-dirty-bitmap.c b/migration/block-dirty-bitmap.c index 5bef793ac0..98921db772 100644 --- a/migration/block-dirty-bitmap.c +++ b/migration/block-dirty-bitmap.c @@ -562,8 +562,9 @@ static int add_bitmaps_to_list(DBMSaveState *s, BlockDriverState *bs, dbms->bitmap_alias = g_strdup(bitmap_alias); dbms->bitmap = bitmap; dbms->total_sectors = bdrv_nb_sectors(bs); - dbms->sectors_per_chunk = CHUNK_SIZE * 8 * - bdrv_dirty_bitmap_granularity(bitmap) >> BDRV_SECTOR_BITS; + dbms->sectors_per_chunk = CHUNK_SIZE * 8LLU * + (bdrv_dirty_bitmap_granularity(bitmap) >> BDRV_SECTOR_BITS); + assert(dbms->sectors_per_chunk != 0); if (bdrv_dirty_bitmap_enabled(bitmap)) { dbms->flags |= DIRTY_BITMAP_MIG_START_FLAG_ENABLED; }