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

[Borislav Petkov]

On Mon, Apr 07, 2025 at 09:58:48AM +1000, Kevin Koster wrote:
> But I like to know Linux really works on the hardware it's built for,

I don't know what that means.

> and I'm not much better, writing this now on a Pentium 1.

Lemme guess: this is your main machine you use for daily work?

:-\

> > -	if (dis_ucode_ldr || c->x86_vendor != X86_VENDOR_AMD || c->x86 < 0x10)
> > +	if (microcode_loader_disabled() || c->x86_vendor != X86_VENDOR_AMD || c->x86 < 0x10)
> 		return 0;
> 
> Still fails unless the native_cpuid_eax(1) call is moved under here. After that
> change, it boots fine.

Please show me with a diff what you're doing because I don't know what you
mean.

I did this:

bool have_cpuid_p(void)
{
        return false;
}

in order to simulate no CPUID support but my 32-bit guest boots fine.

Also, send a full dmesg from that machine so that I can try to reproduce here.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette