From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43723) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dQAva-0004f3-PG for qemu-devel@nongnu.org; Wed, 28 Jun 2017 07:14:35 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dQAvW-0003tW-NR for qemu-devel@nongnu.org; Wed, 28 Jun 2017 07:14:34 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37214) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dQAvW-0003tB-F1 for qemu-devel@nongnu.org; Wed, 28 Jun 2017 07:14:30 -0400 References: <20170628083704.24997-1-haozhong.zhang@intel.com> From: Paolo Bonzini Message-ID: <2f01750b-8ab5-dd73-1d0e-2efc86f427ee@redhat.com> Date: Wed, 28 Jun 2017 13:14:23 +0200 MIME-Version: 1.0 In-Reply-To: <20170628083704.24997-1-haozhong.zhang@intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v2] 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: Haozhong Zhang , qemu-devel@nongnu.org Cc: Stefan Hajnoczi , Juan Quintela , Xiao Guangrong On 28/06/2017 10:37, Haozhong Zhang wrote: > 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 > --- > Changes in v2: > * Avoid shadowing variable 'offset'. (Paolo) > --- > include/exec/ram_addr.h | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h > index 73d1bea8b6..c04f4f67f6 100644 > --- a/include/exec/ram_addr.h > +++ b/include/exec/ram_addr.h > @@ -386,8 +386,9 @@ 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 + rb->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(); > @@ -414,9 +415,11 @@ uint64_t cpu_physical_memory_sync_dirty_bitmap(RAMBlock *rb, > > rcu_read_unlock(); > } else { > + ram_addr_t offset = rb->offset; > + > 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; > Acked-by: Paolo Bonzini Juan, please take care of this yourself! Thanks, Paolo