From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [PATCH 5/5] ioeventfd: Introduce KVM_IOEVENTFD_FLAG_SOCKET Date: Tue, 19 Jul 2011 21:52:23 -0500 Message-ID: <4E2642E7.3020602@codemonkey.ws> References: <1309927078-5983-1-git-send-email-levinsasha928@gmail.com> <4E1D442E.6090308@redhat.com> <4E1D9623.70801@redhat.com> <4E1D9E75.1070901@redhat.com> <4E1E9A3B.7090200@kernel.org> <4E1EA455.4010608@redhat.com> <4E1EA8A2.9020304@redhat.com> <4E1EBB7A.3030809@redhat.com> <4E1ED913.6070003@redhat.com> <1310646737.21171.23.camel@lappy> <4E1EE519.1020608@redhat.co m> <1310648409.21171.34.camel@lappy> <4E1EE9A5.8040306@redhat.com> <1310649431.9498.28.camel@jaguar> <4E1EEDBB.10206@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Pekka Enberg , Sasha Levin , "Michael S. Tsirkin" , kvm@vger.kernel.org, Ingo Molnar , Marcelo Tosatti To: Avi Kivity Return-path: Received: from mail-gy0-f174.google.com ([209.85.160.174]:43314 "EHLO mail-gy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752523Ab1GTCw0 (ORCPT ); Tue, 19 Jul 2011 22:52:26 -0400 Received: by gyh3 with SMTP id 3so2075106gyh.19 for ; Tue, 19 Jul 2011 19:52:25 -0700 (PDT) In-Reply-To: <4E1EEDBB.10206@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 07/14/2011 08:23 AM, Avi Kivity wrote: > On 07/14/2011 04:17 PM, Pekka Enberg wrote: >> > >> > I still don't follow. The guest oopses? dmesg | less. An issue with >> > tools/kvm? gdb -p `pgrep kvm`. >> >> When I was debugging tools/kvm virtio code, I used to 'instrument' the >> guest kernel with printk() calls which helped a lot. >> > > Sure, but do you really need it spewing out the serial port all the time? > >> Also, a bug in tools/kvm can manifest in many interesting ways in the >> guest kernel during boot, for example. You can't do dmesg then and gdb >> won't save you. I think you've lived too long in the table KVM and Qemu >> land to remember how important reliable printk() is for development. > > I guess. Also I've switched to trace_printk() since it's much nicer (and > intergrates with other ftrace features). > > And again, I'm not against tools/kvm optimizing serial. I just want > better justification for socket-mmio. Just to be really thorough, the optimization is incorrect for UART emulation. Maybe for a simple PIO based console where there were no guest visible side effects to a character write, this would be okay, but that is not how a UART works. Just implement virtio-serial :-) You can move data as fast as you'd like through it. And if virtio-serial is too complicated, make a simpler version that doesn't have such crazy semantics. Regards, Anthony Liguori >