linux-kernel - Re: 2.6.39-rc5-git2 boot crashs

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Date:	Tue, 3 May 2011 14:45:10 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	"H. Peter Anvin" <hpa@...or.com>, werner <w.landgraf@...ru>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: 2.6.39-rc5-git2 boot crashs

On Tue, May 3, 2011 at 1:50 PM, Ingo Molnar <mingo@...e.hu> wrote:
>
> the ELAN .config option influences the following details:
>
>  - sets X86_L1_CACHE_SHIFT to 4 (16 bytes) instead of the typical 6 (64 bytes)
>  - sets X86_ALIGNMENT_16
>  - sets the -march=i486 compiler flag

It also does this to the config diff:

  306,307c328,332
  < CONFIG_X86_ALIGNMENT_16=y
  < CONFIG_X86_MINIMUM_CPU_FAMILY=4
  ---
  > CONFIG_X86_USE_PPRO_CHECKSUM=y
  > CONFIG_X86_TSC=y
  > CONFIG_X86_CMPXCHG64=y
  > CONFIG_X86_CMOV=y
  > CONFIG_X86_MINIMUM_CPU_FAMILY=5

because of all the indirect changes it causes.

Now, Werner is actually _running_ on an AMD Opteron (or whatever
family 15 is), I think. And his kernel is SMP-enabled. And that whole
thin looks really really iffy.

How/why do we even allow that combination of SMP and (for example)
arch/x86/lib/atomic64_386_32.S to be picked?

I don't think he actually runs SMP, but the fact that we even allow
that combination looks really odd/iffy. Am I missing something?

                        Linus
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