linux-kernel - Re: [PATCH] x86/boot: Fail the boot if !M486 and CPUID is missing

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Message-ID: <20161130131812.5a99e3ac@lxorguk.ukuu.org.uk>
Date:   Wed, 30 Nov 2016 13:18:12 +0000
From:   One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     x86@...nel.org, Borislav Petkov <bp@...en8.de>,
        linux-kernel@...r.kernel.org, Brian Gerst <brgerst@...il.com>,
        Matthew Whitehead <tedheadster@...il.com>
Subject: Re: [PATCH] x86/boot: Fail the boot if !M486 and CPUID is missing

> Rather than trying to work around these issues, just have the kernel
> fail loudly if it's running on a CPUID-less 486, doesn't have CPUID,
> and doesn't have CONFIG_M486 set.

NAK

This still breaks the Geode at the very least and I think the ELAN and
some of the other older socket 7 devices. These have their own config CPU
type (and in some cases *need* it selected) but do not have CPUID.

Given the cores without CPUID are often post 486 in other respects this
seems a bit odd. In fact I can't help thinking that the problem is that
sync_core tests CONFIG_M486 whereas we should have and test

HAVE_CPUID

and set this by processor type (M586/M486/GEODEGX1/GEODE_LX1/Cyrix plus I
think ELAN not having it)

I'd been wondering why Geode wasn't working on modern kernels, now I
think I know 8)

Alan