From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45482) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z7WGG-0005He-IO for qemu-devel@nongnu.org; Tue, 23 Jun 2015 18:01:46 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Z7WGB-0003W6-KT for qemu-devel@nongnu.org; Tue, 23 Jun 2015 18:01:44 -0400 Received: from cantor2.suse.de ([195.135.220.15]:48820 helo=mx2.suse.de) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z7WGB-0003Vs-EE for qemu-devel@nongnu.org; Tue, 23 Jun 2015 18:01:39 -0400 Message-ID: <5589D740.1010004@suse.de> Date: Wed, 24 Jun 2015 00:01:36 +0200 From: Alexander Graf MIME-Version: 1.0 References: <1434984574-21037-1-git-send-email-dgilbert@redhat.com> <558889A7.2020408@suse.de> <20150623163706.GE2167@work-vm> In-Reply-To: <20150623163706.GE2167@work-vm> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] Peek dont read for vmdescription List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Dr. David Alan Gilbert" Cc: amit.shah@redhat.com, qemu-devel@nongnu.org, quintela@redhat.com On 23.06.15 18:37, Dr. David Alan Gilbert wrote: > * 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? > > Yeh, scrap this patch. > > I've just posted > > 'Only try and read a VMDescription if it should be there' > > as a replacement. > Fundamentally, the trick of trying to send/read stuff after the EOF > just isn't safe on all transports. We've got to read stuff if it's > expected and only if it's expected and obey the EOF marker. If it > wasn't for keeping compatibility I'd swing this section around so it > went before the EOF, but we can't break compatibility with streams > that already have it. Meh, that's truly a shame. The post-things-after-EOF-hack sounded so great... Alex