Re: [gentoo-user] AMD microcode updates - where are they?!

[Corbin <corbinbird@charter.net>]

On 7/14/19 8:26 AM, Mick wrote:
> Then I came across this old message regarding Piledriver CPUs:
> https://lists.debian.org/debian-security/2016/03/msg00084.html The
> post refers to model 2 of cpu family 21. Not all models in the same
> family, only model 2. So I am thinking although patch files are named
> per CPU family, whether they are applicable and applied as an update
> to the CPU is probably determined by the particular CPU *model*.
> Logically, errata in previous CPU revisions may have been fixed in
> later models of the same family and therefore such microcode updates
> would not be needed. When offered by the OS the CPU won't select to
> have them applied. This explains why my AMD models, which are later
> revisions of the same 15h family do not apply any microcode updates -
> they don't need them. Please share if you know differently and thank
> you all for your responses. 
Remember a while back when I mentioned that "lwp" had disappeared from
my /proc/cpuinfo?
They restored "lwp" with this commit :
> https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/commit/?id=7518922bd5b98b137af7aaf3c836f5a498e91609
So it stands to reason that the microcode only applies specific patches
to specific problems per CPU.


Reference :
> Darkstar ~ # cat /proc/cpuinfo
> processor    : 0
> vendor_id    : AuthenticAMD
> cpu family    : 21
> model        : 2
> model name    : AMD FX(tm)-9590 Eight-Core Processor
> stepping    : 0
> microcode    : 0x6000852
> cpu MHz        : 4685.390
> cache size    : 2048 KB
Output of /sys/devices/system/cpu/vulnerabilities :
>
> Darkstar ~ # cat /sys/devices/system/cpu/vulnerabilities/l1tf
> Not affected
> Darkstar ~ # cat /sys/devices/system/cpu/vulnerabilities/mds
> Not affected
> Darkstar ~ # cat /sys/devices/system/cpu/vulnerabilities/meltdown
> Not affected
> Darkstar ~ # cat
> /sys/devices/system/cpu/vulnerabilities/spec_store_bypass
> Mitigation: Speculative Store Bypass disabled
> Darkstar ~ # cat /sys/devices/system/cpu/vulnerabilities/spectre_v1
> Mitigation: __user pointer sanitization
> Darkstar ~ # cat /sys/devices/system/cpu/vulnerabilities/spectre_v2
> Mitigation: Full AMD retpoline, IBPB: always-on, STIBP: disabled, RSB
> filling

Corbin