From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45589) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z7Ji4-0000QB-3r for qemu-devel@nongnu.org; Tue, 23 Jun 2015 04:37:37 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Z7Jhz-0004kk-61 for qemu-devel@nongnu.org; Tue, 23 Jun 2015 04:37:36 -0400 Received: from mx1.redhat.com ([209.132.183.28]:55681) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z7Jhz-0004kg-0k for qemu-devel@nongnu.org; Tue, 23 Jun 2015 04:37:31 -0400 Date: Tue, 23 Jun 2015 09:37:26 +0100 From: "Dr. David Alan Gilbert" Message-ID: <20150623083726.GA2167@work-vm> References: <1434984574-21037-1-git-send-email-dgilbert@redhat.com> <558889A7.2020408@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <558889A7.2020408@suse.de> Subject: Re: [Qemu-devel] [PATCH] Peek dont read for vmdescription List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alexander Graf Cc: amit.shah@redhat.com, qemu-devel@nongnu.org, quintela@redhat.com * Alexander Graf (agraf@suse.de) wrote: > > > On 22.06.15 16:49, Dr. David Alan Gilbert (git) wrote: > > From: "Dr. David Alan Gilbert" > > > > The VMDescription section maybe after the EOF mark, the current code > > does a 'qemu_get_byte' and either gets the header byte identifying the > > description or an error (which it ignores). Doing the 'get' upsets > > RDMA which hangs on old machine types without the VMDescription. > > > > Using 'qemu_peek_byte' avoids that. > > > > Signed-off-by: Dr. David Alan Gilbert > > Fun. I did actually use peek at first and then figured it's the same as > read in the qemu file implementation. Have you figured out why exactly > peek does make a difference for the RDMA case? Hmm, no, I agree that is odd but I do need to look again at it. I started off with a simple empty VM (no guest running) and found that it wouldn't migrate over RDMA using machine types older than 2.3 unless I sent the vmdesc, and this seems to fix that for me. However, I've found another case; a busy migrate running stressapp that still fails on older machine types. My guess is that it depends whether we've read the data already - if we're lucky and the data is already in the qemu-file buffer it doesn't end up calling the RDMA code again. Dave > > > Alex -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK