Minimum CPUID extended level in longmode?

[tehmav]

Hi!

Since my OS is 64bit only, with a 16/32bit bootstrap, I just wanted to ask if there is a minimum extended level (higher than 0x8000_0001 of course) of CPUID required by longmode.

It would be just nice to know

Cheers!

[stlw]

Yes, leaf 0x80000008 present for every CPU with long to state maximum virtual address width.

Stanislav

[tehmav]

Thank you for your answer!

And just to be sure: This means that in long mode CPUID will always report a supported extended level of atleast 0x8000_0008?

[stlw]

Thank you for your answer!

And just to be sure: This means that in long mode CPUID will always report a supported extended level of atleast 0x8000_0008?

Yes. But why should you care for CPUID leafs which you don't get useful information from ?

[tehmav]

This is more of a thing which, for me personally, could be good to know.