linux-kernel - Re: [3.9-rc1] Bug in bootup code or debug code?

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Message-Id: <201303132224.BEC60922.JStQOFMVFFOHLO@I-love.SAKURA.ne.jp>
Date:	Wed, 13 Mar 2013 22:24:27 +0900
From:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:	fenghua.yu@...el.com, hpa@...ux.intel.com
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [3.9-rc1] Bug in bootup code or debug code?

Tetsuo Handa wrote:
> Tetsuo Handa wrote:
> > Hello.
> > 
> > I can boot linux-next-20130205 using kernel config at
> > http://I-love.SAKURA.ne.jp/tmp/config-3.8-rc6-next-20130205 .
> > But I get VMware's virtual machine kernel stack fault (hardware reset) as soon
> > as kernel is loaded if CONFIG_DEBUG_VIRTUAL=y is added to the config above.
> > 
> > Since I don't get kernel stack fault if CONFIG_DEBUG_VIRTUAL=y is added to
> > kernel config generated by "make allnoconfig", I guess something is wrong with
> > code which is executed at very early stage of bootup.
> > 
> > Any clue?
> > 
> > Regards.
> > 
> 
> This bug is not yet fixed as of 3.9-rc1.
> Should I run git bisect?
> 
> Regards.
> 

I found the location of "hardware reset" trigger.

It is __pa_symbol(&boot_params) call, for I don't encounter "hardware reset" if
I remove the "//" from below debug patch.

This bug is not yet fixed as of 3.9.0-rc2-00188-g6c23cbb .

--- a/arch/x86/kernel/microcode_intel_early.c
+++ b/arch/x86/kernel/microcode_intel_early.c
@@ -741,7 +741,9 @@ load_ucode_intel_bsp(void)
 #ifdef CONFIG_X86_32
        struct boot_params *boot_params_p;

+       //while (1);
        boot_params_p = (struct boot_params *)__pa_symbol(&boot_params);
+       while (1);
        ramdisk_image = boot_params_p->hdr.ramdisk_image;
        ramdisk_size  = boot_params_p->hdr.ramdisk_size;
        initrd_start_early = ramdisk_image;
--
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