[coreboot] When does AMD release the fam15 spectre microcode updates?

[Alberto Bursi]

On 22/05/2018 07:03, Taiidan at gmx.com wrote:
> AMD has at long last coughed up the stuff to the linux-firmware people
>
> https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/diff/amd-ucode/microcode_amd_fam15h.bin?id=77101513943ef198e2050667c87abf19e6cbb1d8
>
> The fam15h microcode update adds IBPB
>
>    * Indirect Branch Prediction Barrier (IBPB)
>      * PRED_CMD MSR is available:  YES
>      * CPU indicates IBPB capability:  YES  (IBPB_SUPPORT feature bit)
>
> The question is what about the other stuff? IBRS, STIBP? This is
> confusing due to zero documentation on these updates from amd...Why
> don't they have those in this update? Would it be possible to easily add
> the support flags without microcode for those who use libreboot?
>

What you mean with "add the support flags without microcode"?

A CPU either supports some instructions (like IBPB) because it actually 
does (i.e. the microcode tells it how to do that), or it does not.

I don't know if you can fake enable these support flags, but I don't 
think it is a good idea at all, at best it would just be a lie, at worst 
it could cause issues (crashing?) if the kernel calls an instruction 
that isn't available (I don't know how that is handled).

-Alberto