From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:39848) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TUExU-0000ms-OD for qemu-devel@nongnu.org; Fri, 02 Nov 2012 06:58:41 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TUExT-0008IY-C4 for qemu-devel@nongnu.org; Fri, 02 Nov 2012 06:58:40 -0400 Received: from mx1.redhat.com ([209.132.183.28]:3729) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TUExT-0008IN-41 for qemu-devel@nongnu.org; Fri, 02 Nov 2012 06:58:39 -0400 From: Juan Quintela In-Reply-To: <20121102031508.GN27695@truffula.fritz.box> (David Gibson's message of "Fri, 2 Nov 2012 14:15:08 +1100") References: <1351654988-13165-1-git-send-email-david@gibson.dropbear.id.au> <509106A0.7020400@redhat.com> <20121102031508.GN27695@truffula.fritz.box> Date: Fri, 02 Nov 2012 11:58:32 +0100 Message-ID: <87625oi84n.fsf@elfo.mitica> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [Qemu-devel] [PATCH] Fix off-by-1 error in RAM migration code Reply-To: quintela@redhat.com List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: David Gibson Cc: Orit Wasserman , aliguori@us.ibm.com, qemu-devel@nongnu.org David Gibson wrote: > On Wed, Oct 31, 2012 at 01:08:16PM +0200, Orit Wasserman wrote: >> On 10/31/2012 05:43 AM, David Gibson wrote: >> > The code for migrating (or savevm-ing) memory pages starts off by creating >> > a dirty bitmap and filling it with 1s. Except, actually, because bit >> > addresses are 0-based it fills every bit except bit 0 with 1s and puts an >> > extra 1 beyond the end of the bitmap, potentially corrupting unrelated >> > memory. Oops. This patch fixes it. >> > >> > Signed-off-by: David Gibson >> > --- >> > arch_init.c | 2 +- >> > 1 file changed, 1 insertion(+), 1 deletion(-) >> > >> > diff --git a/arch_init.c b/arch_init.c >> > index e6effe8..b75a4c5 100644 >> > --- a/arch_init.c >> > +++ b/arch_init.c >> > @@ -568,7 +568,7 @@ static int ram_save_setup(QEMUFile *f, void *opaque) >> > int64_t ram_pages = last_ram_offset() >> TARGET_PAGE_BITS; >> > >> > migration_bitmap = bitmap_new(ram_pages); >> > - bitmap_set(migration_bitmap, 1, ram_pages); >> > + bitmap_set(migration_bitmap, 0, ram_pages); >> > migration_dirty_pages = ram_pages; >> > >> > bytes_transferred = 0; >> > >> You are correct, good catch. >> Reviewed-by: Orit Wasserman > > Juan, > > Sorry, forgot to CC you on the original mailing here, which I should > have done. This is a serious bug in the migration code and we should > apply to mainline ASAP. Reviewed-by: Juan Quintela Good catch, I missunderstood the function when fixing a different bug, and never undrestood why it fixed it. Thanks, Juan.