Re: [PATCH qemu-server v3] fix #5578: smbios: set serial number

[Dominik Csapak <d.csapak@proxmox.com>]

On 4/7/26 5:36 PM, Manuel Federanko wrote:
> On 2026-04-07 3:26 PM, Dominik Csapak wrote:
>> not sure if it was discussed off-list, but you didn't really
>> address fionas comment about just adding this conditionally,
>> e.g. via ostype or machine version
>>
>> this will increase the config size by a bit and i guess
>> most guest operating systems don't gain much from this?
>>
>> i'm guilty of adding such flags unconditionally myself in the past
>> (see vmgenid) but i think we should avoid that when possible
>>
>> e.g. an empty config (qm create ID)
>> looks like this currently:
>>
>> ```
>> boot:
>> meta: creation-qemu=10.2.1,ctime=1775568119
>> smbios1: uuid=a0f6c957-1c8b-439f-b25a-1e45dc151263
>> vmgenid: 0ed5ca0d-0e72-4c1a-b62f-ad2f7aaa8819
>> ```
>>
>> with your patch it looks like this:
>>
>> ```
>> boot:
>> meta: creation-qemu=10.2.1,ctime=1775568283
>> smbios1:
>> base64=1,serial=UFZFLWM5OTY3ZDQwLTVlZTUtNDQ1My1hZDI0LTljZWUzODJmZTg1ZA==,uuid=c9967d40-5ee5-4453-ad24-9cee382fe85d
>> vmgenid: 1c7fe857-3520-4a20-8e09-611a7fb1be3b
>> ```
>>
>> which is quite a bit of noise.
> 
> Agreed, I'm against magically setting this if we detect a specific OS,
> since in theory any program on any OS can depend on the serial. Some
> specific Microsoft software is the reason for this patch, but I would
> be surprised if it is the only one.
> 
>>
>> If you think it's worthwhile to have a serial number for every guest,
>> we could e.g. still give it to qemus commandline if it's
>> missing in the config (especially if it's the same as the
>> normal uuid, but prefixed with PVE-)
>> IMHO it makes no sense having the same uuid twice in the config.
>>
>> if someone sets a serial manually, we should use that of course.
> 
> That's a good idea - could there be a use-case of wanting the serial
> to not be set? If that is not the case then I'd prefer this approach.

we probably cannot add it unconditionally, since that might trip up
live-migration (to be tested though). we could think about
guarding with a machine version, or using a special value as serial
(something like 'pve-auto') that gets replaced by the actual
"PVE-uuid' part. that would be shorter and we wouldn't duplicate
the uuid.

> 
>> sorry if any of these were discussed already, i checked the m-l
>> but didn't find any discussion regarding this.
>>
> I'm not sure anymore tbh. I talked about this with Stoiko off-list,
> but it might've only concerned the format/prefix of the serial.
> 
> Anyways thanks for the feedback.