linux-kernel - Re: [qemu64,+smep,+smap] WARNING: CPU: 1 PID: 0 at arch/x86/kernel/cpu/amd.c:220 init

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Message-ID: <20140307220655.GA580@redhat.com>
Date:	Fri, 7 Mar 2014 17:06:55 -0500
From:	Dave Jones <davej@...hat.com>
To:	Borislav Petkov <bp@...en8.de>
Cc:	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Fengguang Wu <fengguang.wu@...el.com>,
	Ingo Molnar <mingo@...nel.org>,
	Yinghai Lu <yhlu.kernel@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [qemu64,+smep,+smap] WARNING: CPU: 1 PID: 0 at
 arch/x86/kernel/cpu/amd.c:220 init_amd()

On Fri, Mar 07, 2014 at 10:38:56PM +0100, Borislav Petkov wrote:

 > * Another option would be if we change the f/m/s of "qemu64" so that
 > the test doesn't fire.
 > 
 > What also makes me wonder is why is this thing even called qemu64?? AMD
 > family 6 was 32-bit only CPUs so 64 is kinda wrong IMO. I mean, the
 > kernel code is in "ifdef CONFIG_X86_32" block so "qemu64" is patently
 > wrong naming.

Additionally, fam:6 model:6 stepping 3 never existed in the real world afaict.
I used to keep x86info's stepping db pretty up to date, and that only has knowledge
of stepping 1 & 2.[*]  Modelling qemu on something from the real world might be
a better idea than inventing new special cases.

 > Oh, and the thing has CPUID_EXT2_LM which is also a WTH moment for me.
 > Paolo, what's going on here?

Yeah, this is a mess, there should be no family < 0xf with LM set.

	Dave

[*] It's possible I somehow missed it, or the AMD rev docs never mentioned it
for some reason, but it seems unlikely.

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