From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43772) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dQ2yF-0001UL-Vl for qemu-devel@nongnu.org; Tue, 27 Jun 2017 22:44:49 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dQ2yB-00089f-9D for qemu-devel@nongnu.org; Tue, 27 Jun 2017 22:44:48 -0400 Received: from mga03.intel.com ([134.134.136.65]:24340) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dQ2yB-00089O-01 for qemu-devel@nongnu.org; Tue, 27 Jun 2017 22:44:43 -0400 From: Haozhong Zhang Date: Wed, 28 Jun 2017 10:43:58 +0800 Message-Id: <20170628024358.29956-1-haozhong.zhang@intel.com> Subject: [Qemu-devel] [PATCH] exec: fix access to ram_list.dirty_memory when sync dirty bitmap List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Paolo Bonzini , Stefan Hajnoczi , Juan Quintela , Xiao Guangrong , Haozhong Zhang In cpu_physical_memory_sync_dirty_bitmap(rb, start, ...), the 2nd argument 'start' is relative to the start of the ramblock 'rb'. When it's used to access the dirty memory bitmap of ram_list (i.e. ram_list.dirty_memory[DIRTY_MEMORY_MIGRATION]->blocks[]), an offset to the start of all RAM (i.e. rb->offset) should be added to it, which has however been missed since c/s 6b6712efcc. For a ramblock of host memory backend whose offset is not zero, cpu_physical_memory_sync_dirty_bitmap() synchronizes the incorrect part of the dirty memory bitmap of ram_list to the per ramblock dirty bitmap. As a result, a guest with host memory backend may crash after migration. Fix it by adding the offset of ramblock when accessing the dirty memory bitmap of ram_list in cpu_physical_memory_sync_dirty_bitmap(). Reported-by: Stefan Hajnoczi Signed-off-by: Haozhong Zhang --- include/exec/ram_addr.h | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h index 73d1bea8b6..cbc797ed05 100644 --- a/include/exec/ram_addr.h +++ b/include/exec/ram_addr.h @@ -377,6 +377,7 @@ uint64_t cpu_physical_memory_sync_dirty_bitmap(RAMBlock *rb, uint64_t *real_dirty_pages) { ram_addr_t addr; + ram_addr_t offset = rb->offset; unsigned long page = BIT_WORD(start >> TARGET_PAGE_BITS); uint64_t num_dirty = 0; unsigned long *dest = rb->bmap; @@ -386,8 +387,9 @@ uint64_t cpu_physical_memory_sync_dirty_bitmap(RAMBlock *rb, int k; int nr = BITS_TO_LONGS(length >> TARGET_PAGE_BITS); unsigned long * const *src; - unsigned long idx = (page * BITS_PER_LONG) / DIRTY_MEMORY_BLOCK_SIZE; - unsigned long offset = BIT_WORD((page * BITS_PER_LONG) % + unsigned long word = BIT_WORD((start + offset) >> TARGET_PAGE_BITS); + unsigned long idx = (word * BITS_PER_LONG) / DIRTY_MEMORY_BLOCK_SIZE; + unsigned long offset = BIT_WORD((word * BITS_PER_LONG) % DIRTY_MEMORY_BLOCK_SIZE); rcu_read_lock(); @@ -416,7 +418,7 @@ uint64_t cpu_physical_memory_sync_dirty_bitmap(RAMBlock *rb, } else { for (addr = 0; addr < length; addr += TARGET_PAGE_SIZE) { if (cpu_physical_memory_test_and_clear_dirty( - start + addr, + start + addr + offset, TARGET_PAGE_SIZE, DIRTY_MEMORY_MIGRATION)) { *real_dirty_pages += 1; -- 2.11.0