From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51706) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dQ7QY-0003zQ-Ir for qemu-devel@nongnu.org; Wed, 28 Jun 2017 03:30:19 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dQ7QU-0005Va-JX for qemu-devel@nongnu.org; Wed, 28 Jun 2017 03:30:18 -0400 Received: from mx1.redhat.com ([209.132.183.28]:58244) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dQ7QU-0005VH-AO for qemu-devel@nongnu.org; Wed, 28 Jun 2017 03:30:14 -0400 From: Juan Quintela In-Reply-To: <20170628024358.29956-1-haozhong.zhang@intel.com> (Haozhong Zhang's message of "Wed, 28 Jun 2017 10:43:58 +0800") References: <20170628024358.29956-1-haozhong.zhang@intel.com> Reply-To: quintela@redhat.com Date: Wed, 28 Jun 2017 09:30:01 +0200 Message-ID: <87zics7eo6.fsf@secure.mitica> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [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: Haozhong Zhang Cc: qemu-devel@nongnu.org, Paolo Bonzini , Stefan Hajnoczi , Xiao Guangrong 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 Reviewed-by: Juan Quintela As this function is only used on migration, should I integrate it on my next push, or do you want to pull it, Paolo? Later, Juan. > --- > 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;