On 2019-07-17 07:46, Corbin wrote:

> My kernel version : 4.19.59
> 
> Please note that I am using the "experimental" USE FLAG for
> "sys-kernel/gentoo-sources".
> 
> CPU selected is "AMD Piledriver"
> 
> Also, I am using the latest firmware for "sys-kernel/linux-firmware" (
> 20190712:0 ).
> 
> Kernel command line parameters on boot :
> 
> "spectre_v2=on spectre_v2_user=on spec_store_bypass_disable=on"

A couple paragraphs down in that redhat article it says:

    Red Hat Enterprise Linux defaults on AMD CPUs: Due to the
    differences in underlying hardware implementation, AMD X86 systems
    are not vulnerable to variant #3. The correct default values will be
    set on AMD hardware based on dynamic checks during the boot
    sequence.

    pti=0 ibrs=0 ibpb=1 retp=1 -> fix variant #1 #2 if the microcode update is 
applied
    pti=0 ibrs=2 ibpb=1 retp=1 -> fix variant #1 #2 on older processors that 
can disable indirect branch prediction without microcode updates

    Note: A microcode patch provided by the vendor must be applied in order for 
the tunables to be visible.

which of course is self-contradictory, so not a full answer but maybe a
clue.

Are those settings meant to go on a boot command line?

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