SMBIOS UUID

SMBIOS UUID

[Dejan Markic]

Hello all,

sorry, as this might be a stupid question for some of you, but I wonder 
why here:

https://github.com/mirage/xen/blob/master/tools/firmware/hvmloader/smbios.c#L438

You allow almost everything to be overwritten in SMBIOS type 1 table 
except the UUID. Would there be any problems if UUID was also picked up 
from xenstore with, for instance, HVM_XS_SYSTEM_UUID?

Thank you and kind regards,
Dejan

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Re: SMBIOS UUID

[Andrew Cooper]

On 12/12/16 19:05, Dejan Markic wrote:
> Hello all,
>
> sorry, as this might be a stupid question for some of you, but I
> wonder why here:
>
> https://github.com/mirage/xen/blob/master/tools/firmware/hvmloader/smbios.c#L438
>
>
> You allow almost everything to be overwritten in SMBIOS type 1 table
> except the UUID.

Probably only because whomever implemented the code didn't need to do that.

> Would there be any problems if UUID was also picked up from xenstore
> with, for instance, HVM_XS_SYSTEM_UUID?

The UUID is currently picked up from the domain's UUID stored in Xen, so
is currently under toolstack control.

I don't see a particular problem with being able to specify it via
xenstore.  What is your usecase here?

~Andrew

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Re: SMBIOS UUID

[Dejan Markic]

Hello Andrew,

firstly, thank you for your answer. We have some software being moved 
from physical machines to virtual machines and we need to maintain those 
UUID's. I've been able to change the hvmloader to staticly change the 
UUID. It seems that xenstore uses fixed database scheme, so I guess I 
would first have to request a change in that scheme to also make it 
possible to specify product-uuid or similar in bios-strings and than it 
would be fairly trivial to use xenstore_* functions to get this and use 
it if specified.

If I understand this correctly, xenstore is under XAPI development? I 
can also provide the patch fro hvmloader to use this new xenstore 
propery in bios-strings.

It's fairly easy to change this in vmWare or HyperV.

Thank you and kind regards,
Dejan

On 15.12.2016 17:07, Andrew Cooper wrote:
> On 12/12/16 19:05, Dejan Markic wrote:
>> Hello all,
>>
>> sorry, as this might be a stupid question for some of you, but I
>> wonder why here:
>>
>> https://github.com/mirage/xen/blob/master/tools/firmware/hvmloader/smbios.c#L438
>>
>>
>> You allow almost everything to be overwritten in SMBIOS type 1 table
>> except the UUID.
> Probably only because whomever implemented the code didn't need to do that.
>
>> Would there be any problems if UUID was also picked up from xenstore
>> with, for instance, HVM_XS_SYSTEM_UUID?
> The UUID is currently picked up from the domain's UUID stored in Xen, so
> is currently under toolstack control.
>
> I don't see a particular problem with being able to specify it via
> xenstore.  What is your usecase here?
>
> ~Andrew


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Re: SMBIOS UUID

[Andrew Cooper]

On 17/12/16 10:54, Dejan Markic wrote:
> Hello Andrew,
>
> firstly, thank you for your answer. We have some software being moved
> from physical machines to virtual machines and we need to maintain
> those UUID's.

Excellent use case.  Given this, I switch my view to definitely being a
good idea to be able to control that field like the others.

> I've been able to change the hvmloader to staticly change the UUID. It
> seems that xenstore uses fixed database scheme, so I guess I would
> first have to request a change in that scheme to also make it possible
> to specify product-uuid or similar in bios-strings and than it would
> be fairly trivial to use xenstore_* functions to get this and use it
> if specified.

docs/misc/xenstore-paths.markdown is the canonical description of which
paths mean what, although it appears that existing bios-strings/ paths
were never entered into it.  (Documentation was sadly lacking in the
past, which is why the documents are now plain-text in the source tree)

>
> If I understand this correctly, xenstore is under XAPI development? I
> can also provide the patch fro hvmloader to use this new xenstore
> propery in bios-strings.

Which toolstack are you using?  Xapi from XenServer, or xl/libxl from
upstream Xen?

The hvmloader part would be the same either way, and looking at the
source code history, c/s c74c1f906a is the only example we have of
adding a new string.  The header file formally describing the toolstack
/ hvmloader API post-dates the API existing, but was introduced by a
load of other changes, so c/s 4d23036e7 is also an interesting read.

~Andrew

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