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

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Date:	Wed, 13 Mar 2013 10:44:51 -0700
From:	"H. Peter Anvin" <hpa@...ux.intel.com>
To:	"Yu, Fenghua" <fenghua.yu@...el.com>
CC:	"dave@...ux.vnet.ibm.com" <dave@...ux.vnet.ibm.com>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [3.9-rc1] Bug in bootup code or debug code?

On 03/13/2013 08:22 AM, Yu, Fenghua wrote:
>>
>> 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;
> 
> Tetsuo and Dave,
> 
> That's the place where we suspected to cause the problem.
> 
> My question is: how to access global variable in linear mode in virtualization? __pa_symbol() is not a problem for native.
> 

What kind of virtualization are we talking about here?  We should not be
running this code under any paravirtualized code path -- this is the
hypervisor's job to take care of this.  For HVM, this should just work
the same way.

	-hpa


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