From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:58701) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RPzie-0003DT-Mm for qemu-devel@nongnu.org; Mon, 14 Nov 2011 11:49:17 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1RPziZ-0000e6-TZ for qemu-devel@nongnu.org; Mon, 14 Nov 2011 11:49:16 -0500 Received: from mail-yw0-f45.google.com ([209.85.213.45]:53384) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RPziZ-0000e2-Ok for qemu-devel@nongnu.org; Mon, 14 Nov 2011 11:49:11 -0500 Received: by ywa17 with SMTP id 17so2960775ywa.4 for ; Mon, 14 Nov 2011 08:49:11 -0800 (PST) Message-ID: <4EC14683.1030800@codemonkey.ws> Date: Mon, 14 Nov 2011 10:49:07 -0600 From: Anthony Liguori MIME-Version: 1.0 References: <1321043378-15344-1-git-send-email-aliguori@us.ibm.com> <1321043378-15344-3-git-send-email-aliguori@us.ibm.com> <4EC140E3.1070001@codemonkey.ws> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 3/4] qcow2: add a migration blocker List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi Cc: Kevin Wolf , Lucas Meneghel Rodrigues , Juan Quintela , qemu-devel@nongnu.org, Stefan Hajnoczi On 11/14/2011 10:45 AM, Stefan Hajnoczi wrote: > On Mon, Nov 14, 2011 at 4:25 PM, Anthony Liguori wrote: >> On 11/14/2011 09:51 AM, Stefan Hajnoczi wrote: >>> >>> On Fri, Nov 11, 2011 at 8:29 PM, Anthony Liguori >>> wrote: >>>> >>>> +#define QERR_BLOCK_FORMAT_FEATURE_NOT_SUPPORTED \ >>>> + "{ 'class': 'BlockFormatFeatureNotSupported', 'data': { 'format': >>>> %s, 'name': %s, 'feature': %s } }" >>>> + >>> >>> Isn't having a separate error going to make life harder for management >>> tool writers? I would have expected one "migration not supported" >>> error, regardless of whether the reason is ivshmem, qcow2, or anything >>> else. >> >> Errors shouldn't be tied to verbs. IOW, if you have a migrate command, you >> don't want to have a MigrationFailed error because that's tied to a specific >> verb. >> >> Instead, you want the errors to provide additional information about the >> verb failed. In this case, the verb is failing because you're requesting to >> use a feature that is not supported by this particular block format. > > Okay, this error is semantically different from the earlier error in > this series. > > We need QMP documentation updates in this series so management tool > writers know to look out for. Otherwise libvirt and friends can only > provide generic "This operation failed. Opaque QEMU error:" > rather than responding with graceful error handling. Current QMP documentation does not document errors. The QAPI changes document the errors but it also changes the error paths such that you can do this in a sane fashion. So I agree with you 100% but it's a bigger thing than just this series. Regards, Anthony Liguori > > Stefan >