[Qemu-devel] Re: [PATCH 0/3]: Add UUID command-line option

[Anthony Liguori <anthony@codemonkey.ws>]

Chris Lalancette wrote:
> Anthony Liguori wrote:
>   
>>> Hm, but that's basically what this does, in combination with the Bochs BIOS.
>>> Once the Bochs BIOS reaches the rombios32 code, it makes the calls into the
>>> device model VMware backdoor to get the UUID.  Assuming this all succeeds, the
>>> Bochs BIOS then plumbs it into the SMBIOS tables.
>>>   
>>>       
>> Are there patches for the Bochs BIOS to do this?  Why wouldn't it just 
>> use CMOS to get at the UUID?
>>     
>
> Yeah, there's a uuid_probe() function that's already been merged into the Bochs
> BIOS, and subsequently to most of the downstream projects (including KVM).
>
> void uuid_probe(void)
> {
> #ifdef BX_QEMU
>     uint32_t eax, ebx, ecx, edx;
>
>     // check if backdoor port exists
>     asm volatile ("outl %%eax, %%dx"
>         : "=a" (eax), "=b" (ebx), "=c" (ecx), "=d" (edx)
>         : "a" (0x564d5868), "c" (0xa), "d" (0x5658));
>     if (ebx == 0x564d5868) {
>         uint32_t *uuid_ptr = (uint32_t *)bios_uuid;
>         // get uuid
>         asm volatile ("outl %%eax, %%dx"
>             : "=a" (eax), "=b" (ebx), "=c" (ecx), "=d" (edx)
>             : "a" (0x564d5868), "c" (0x13), "d" (0x5658));
>         uuid_ptr[0] = eax;
>         uuid_ptr[1] = ebx;
>         uuid_ptr[2] = ecx;
>         uuid_ptr[3] = edx;
>     } else
> #endif
>     {
>         // UUID not set
>         memset(bios_uuid, 0, 16);
>     }
> }
>   

That makes me sad that they merged that.  What a terribly complicated 
way to do something that's relatively simple.

Regards,

Anthony Liguori

> Later on in the rombios32 code the bios_uuid[] is used to build up the SMBIOS
> tables.
>
> Chris Lalancette
>