Re: [PATCH] x86/microcode: Fix crashes on early 486 CPUs due to usage of 'cpuid'.

[Kevin Koster]

On Sun, 6 Apr 2025 16:40:49 +1000
Kevin Koster <lkml@xxxxxxxxxxxxx> wrote:
> On Sat, 5 Apr 2025 11:32:26 +0200
> Borislav Petkov <bp@xxxxxxxxx> wrote:
> > On Sat, Apr 05, 2025 at 01:03:06PM +1100, Kevin Koster wrote:
> > > On Sat, 19 Oct 2024 08:29:04 +0200
> > > Oerg866 <oerg866@xxxxxxxxxxxxxx> wrote:
> > > > Starting with v6.7-rc1, the kernel was no longer able to boot on
> > > > early i486-class CPUs.
> > > 
> > > Thanks for this patch! It solves my problem with kernel 6.12.11
> > > rebooting at start-up on 486 CPUs, which had me puzzled. (tested
> > > on AM486DX2-66 and CX486DX4-100)
> > > 
> > > Is there a reason why the patch wasn't accepted?
> > 
> > Yes, too many patches, too little time. :-(
> > 
> > Anyway, does the one below - only build-tested - work for both y'all
> > too?
> 
> On my AM486DX2-66 it gets past the immediate reboot problem but gets
> an Oops and kernel panic here:

But if I move "cpuid_1_eax = native_cpuid_eax(1);" to after the
microcode_loader_disabled() check in amd.c, like in the first patch, it
boots fine!