From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47708) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1b2ZaT-0006PQ-TD for qemu-devel@nongnu.org; Tue, 17 May 2016 03:38:45 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1b2ZaK-0004Ye-SL for qemu-devel@nongnu.org; Tue, 17 May 2016 03:38:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:55465) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1b2ZaK-0004Ya-M8 for qemu-devel@nongnu.org; Tue, 17 May 2016 03:38:32 -0400 Date: Tue, 17 May 2016 10:38:29 +0300 From: "Michael S. Tsirkin" Message-ID: <20160517103744-mutt-send-email-mst@redhat.com> References: <1462508442-9407-1-git-send-email-caoj.fnst@cn.fujitsu.com> <1462508442-9407-10-git-send-email-caoj.fnst@cn.fujitsu.com> <573878E7.7070807@redhat.com> <573ACAA2.1040107@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <573ACAA2.1040107@cn.fujitsu.com> Subject: Re: [Qemu-devel] [PATCH v5 09/11] pci bridge dev: change msi property type List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Cao jin Cc: Marcel Apfelbaum , qemu-devel@nongnu.org, Markus Armbruster On Tue, May 17, 2016 at 03:39:14PM +0800, Cao jin wrote: > > > On 05/15/2016 09:25 PM, Marcel Apfelbaum wrote: > >On 05/06/2016 07:20 AM, Cao jin wrote: > >> From bit to enum OnOffAuto. > >> > >>cc: Michael S. Tsirkin > >>cc: Markus Armbruster > >>cc: Marcel Apfelbaum > >>Signed-off-by: Cao jin > >>--- > >> > >>Actually, I am not quite sure this device need this change, RFC. > >> > > > >Well, it already has the 'msi' property, so we may want to make it > >standard 'OnOffAuto'. > >One problem I can see is the change of semantics. Until now msi=on means > >'auto'. From now on > >it means 'force msi=on', fail otherwise. If I got this right, old > >machines having msi=on > >will failed to start on platforms with msibroken=true, right? > > Exactly, and patch 11 indeed has semantics change. According to what we > discussed before: "if user want msi=on explicitly on command line, then > msi_init`s failure should result in failing to create device", this > semantics change seems can`t be avoid. > > >Maybe we should preserve the semantics for old machines? (this patch > >does not actually > >affect the semantics, but patch 11/11 should, otherwise why change it to > >OnOffAuto, right? ) > > IMHO, in this case, keep compat maybe a burden on us, and make command-line > confusing. See my understanding: > > before: > command line format is msi=on/off, and 'on' means auto > > now: > we change command line to msi=on/off/auto, and keep compat is meaning 'on' > still means auto? If so, why need 'auto' > > So, I am thinking, maybe we can help old machine user update their > configuration, I mean: when they set msi=on on platforms with > msibroken=true, they definitely fail, so we should give a clear hint in > error message to help them know what should do to start the machine, like > "please use msi=auto and try again" Personally I don't consider this a big issue. I don't think many people specify msi=on. > -- > Yours Sincerely, > > Cao jin >