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Date: Mon, 14 Nov 2011 10:25:07 -0600
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: Re: [Qemu-devel] [PATCH 3/4] qcow2: add a migration blocker
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To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Lucas Meneghel Rodrigues <lmr@redhat.com>, qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>, Juan Quintela <quintela@redhat.com>

On 11/14/2011 09:51 AM, Stefan Hajnoczi wrote:
> On Fri, Nov 11, 2011 at 8:29 PM, Anthony Liguori<aliguori@us.ibm.com>  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.

Regards,

Anthony Liguori

>
> Stefan
>