[libvirt] [PATCH] qemuDomainDiskChangeSupported: Forbid alias change

Michal Privoznik mprivozn at redhat.com
Fri Jan 5 08:20:08 UTC 2018


On 01/05/2018 01:15 AM, John Ferlan wrote:
> 
> 
> On 12/13/2017 09:30 AM, Michal Privoznik wrote:
>> Since we have user aliases it may happen that users want to
>> change it using 'update-device'. Instead of ignoring it silently,
>> error out loudly.
>>
>> Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
>> ---
>>  src/qemu/qemu_domain.c | 8 ++++++++
>>  1 file changed, 8 insertions(+)
>>
> 
> So IIUC this would be adding a check that the libvirt supplied alias
> matches, true? But your goal is to check if a "ua-" prefixed alias was
> being used - so should the check use of the prefix?

I don't think this is limited to user provided aliases only. For
instance, libvirt generates the following aliases for disks: scsi0-0-0,
ide0-1-0, fdc0-0-0.

Now, what should happen if an user provides new disk XML trying to
change nothing but 'scsi0-0-0' to say 'scsi0-0-1' (for live domain)? I
think it should be forbidden - we don't have way to change IDs in qemu,
do we? We certainly lack implementation to support it.

Therefore, I think we don't have to limit the check just for 'ua-' prefixes.

> 
> There's probably a few more info. fields that could be considered - any
> thoughts on those? Perhaps fairly difficult to keep up with the various
> _virDomainDiskDef and friends alterations for what this function is
> indicating...

Yeah, probably. I'm not sure. Maybe we will find some more.

Michal




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