From: "H. Hartzer" <h@hartzer.sh>
Subject: Re: Incorrect Meltdown/Spectre mitigation exceptions for AMD64
To: "Philip Guenther" <guenther@gmail.com>
Cc: <tech@openbsd.org>
Date: Fri, 08 Aug 2025 18:17:38 +0000

> Family/model info, as well as relevant cpuid values, can be found in
> the dmesg.  Look for the lines beginning with "cpu0:".
>
>
> Philip Guenther

Hi Philip,

Thank you!

I'm not quite sure how to process this into something I can adjust for.

Here's what I've got:

cpu0 at mainbus0: apid 0 (boot processor)
cpu0: Intel(R) Atom(TM) CPU S1260 @ 2.00GHz, 1995.07 MHz, 06-36-09,
patch 0000010d
cpu0: cpuid 1
edx=bfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CFLUSH,DS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
ecx=40e3bd<SSE3,DTES64,MWAIT,DS-CPL,VMX,EST,TM2,SSSE3,CX16,xTPR,PDCM,MOVBE>
cpu0: cpuid 6 eax=5<SENSOR,ARAT> ecx=1<EFFFREQ>
cpu0: cpuid a vers=3, gp=2, gpwidth=40, ff=3, ffwidth=40
cpu0: cpuid 80000001 edx=20100800<NXE,LONG> ecx=1<LAHF>
cpu0: cpuid 80000007 edx=100<ITSC>
cpu0: MELTDOWN
cpu0: 24KB 64b/line 6-way D-cache, 32KB 64b/line 8-way I-cache, 512KB
64b/line 8-way L2 cache
cpu0: smt 0, core 0, package 0

The replacemeltdown code looks like this:

if (family == 0x6 &&
    (model == 0x37 || model == 0x4a || model == 0x4c ||
     model == 0x4d || model == 0x5a || model == 0x5d ||
     model == 0x6e || model == 0x65 || model == 0x75)) {
	/* Silvermont, Airmont */
	swapgs_vuln = 0;
} else if (family == 0x6 && (model == 0x85 || model == 0x57)) {
	/* KnightsLanding */
	swapgs_vuln = 0;
}

Does the family come from the first octet? So is my family 0x8?

Thanks again!

-Henrich