From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48081) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fb0iJ-0007PK-7g for qemu-devel@nongnu.org; Thu, 05 Jul 2018 05:38:12 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fb0iE-0002SV-Ai for qemu-devel@nongnu.org; Thu, 05 Jul 2018 05:38:11 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:58680 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fb0iE-0002Qw-52 for qemu-devel@nongnu.org; Thu, 05 Jul 2018 05:38:06 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 95E104075626 for ; Thu, 5 Jul 2018 09:38:05 +0000 (UTC) Date: Thu, 5 Jul 2018 10:38:01 +0100 From: "Dr. David Alan Gilbert" Message-ID: <20180705093800.GE2538@work-vm> References: <20180705031755.3254-1-peterx@redhat.com> <20180705031755.3254-4-peterx@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180705031755.3254-4-peterx@redhat.com> Subject: Re: [Qemu-devel] [PATCH for-3.0 3/9] migration: fix incorrect bitmap size calculation List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Xu Cc: qemu-devel@nongnu.org, Juan Quintela * Peter Xu (peterx@redhat.com) wrote: > The calculation on size of received bitmap is incorrect for postcopy > recovery. Here we wanted to let the size to cover all the valid bits in > the bitmap, we should use DIV_ROUND_UP() instead of a division. > > For example, a RAMBlock with size=4K (which contains only one single 4K > page) will have nbits=1, then nbits/8=0, then the real bitmap won't be > sent to source at all. > > Signed-off-by: Peter Xu Reviewed-by: Dr. David Alan Gilbert > --- > migration/ram.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/migration/ram.c b/migration/ram.c > index fbeb23f750..203c691ded 100644 > --- a/migration/ram.c > +++ b/migration/ram.c > @@ -235,7 +235,7 @@ int64_t ramblock_recv_bitmap_send(QEMUFile *file, > bitmap_to_le(le_bitmap, block->receivedmap, nbits); > > /* Size of the bitmap, in bytes */ > - size = nbits / 8; > + size = DIV_ROUND_UP(nbits, 8); > > /* > * size is always aligned to 8 bytes for 64bit machines, but it > @@ -3944,7 +3944,7 @@ int ram_dirty_bitmap_reload(MigrationState *s, RAMBlock *block) > int ret = -EINVAL; > QEMUFile *file = s->rp_state.from_dst_file; > unsigned long *le_bitmap, nbits = block->used_length >> TARGET_PAGE_BITS; > - uint64_t local_size = nbits / 8; > + uint64_t local_size = DIV_ROUND_UP(nbits, 8); > uint64_t size, end_mark; > > trace_ram_dirty_bitmap_reload_begin(block->idstr); > -- > 2.17.1 > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK