Re: [PATCH] hvmloader: Update to SMBIOS 2.6

["Teddy Astie" <teddy.astie@xxxxxxxxxx>]

Le 28/08/2025 à 09:08, Jan Beulich a écrit :
> On 22.08.2025 15:47, Teddy Astie wrote:
>> Currently, hvmloader uses SMBIOS 2.4, however, when using OVMF, the
>> SMBIOS is patched to 2.8, which has clarified the UUID format (as GUID).
>>
>> In Linux, if the SMBIOS version is >= 2.6, the GUID format is used, else
>> (undefined as per SMBIOS spec), big endian is used (used by Xen). Therefore,
>> you have a endian mismatch causing the UUIDs to mismatch in the guest.
>>
>> $ cat /sys/hypervisor/uuid
>> e865e63f-3d30-4f0b-83e0-8fdfc1e30eb7
>> $ cat /sys/devices/virtual/dmi/id/product_uuid
>> 3fe665e8-303d-0b4f-83e0-8fdfc1e30eb7
>> $ cat /sys/devices/virtual/dmi/id/product_serial
>> e865e63f-3d30-4f0b-83e0-8fdfc1e30eb7
>>
>> This patch updates the SMBIOS version from 2.4 to 2.6 and fixup the UUID
>> written in the table; which effectively fix this endianness mismatch with
>> OVMF; while the UUID displayed by Linux is still the same for SeaBIOS.
>
> To update to 2.6, fields new in 2.6 (compared to 2.4) need adding to the
> various structures. First example I ran into is type 4, gaining 5 new
> fields in 2.5.
>

Yes, I add them in a new version along with 2.6 entries for the newly
introduced SMBIOS tables (notably type 9).

> Jan
>

Teddy


Teddy Astie | Vates XCP-ng Developer

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