linux-kernel - Re: [PATCH -v4] x86: Setup early console as early as possible in x86_start

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Message-ID: <4CB364E1.5060303@kernel.org>
Date:	Mon, 11 Oct 2010 12:26:25 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -v4] x86: Setup early console as early as possible in
 x86_start_kernel()

On 10/11/2010 11:37 AM, H. Peter Anvin wrote:
> On 10/11/2010 10:58 AM, Yinghai Lu wrote:
>>  
>>  #ifdef CONFIG_X86_TRAMPOLINE
>> Index: linux-2.6/arch/x86/kernel/head64.c
>> ===================================================================
>> --- linux-2.6.orig/arch/x86/kernel/head64.c
>> +++ linux-2.6/arch/x86/kernel/head64.c
>> @@ -74,6 +74,10 @@ void __init x86_64_start_kernel(char * r
>>  	/* clear bss before set_intr_gate with early_idt_handler */
>>  	clear_bss();
>>  
>> +	/* boot_params is in bss */
>> +	copy_bootdata(__va(real_mode_data));
>> +	setup_early_console();
>> +
>>  	/* Make NULL pointers segfault */
>>  	zap_identity_mappings();
>>  
>> @@ -97,7 +101,14 @@ void __init x86_64_start_kernel(char * r
>>  
>>  void __init x86_64_start_reservations(char *real_mode_data)
>>  {
>> -	copy_bootdata(__va(real_mode_data));
>> +	/*
>> +	 * hdr.version is always not 0, so check it to see
>> +	 *  if boot_params is copied or not.
>> +	 */
>> +	if (!boot_params.hdr.version) {
>> +		copy_bootdata(__va(real_mode_data));
>> +		setup_early_console();
>> +	}
>>  
>>  	memblock_init();
>>  
> 
> Under what conditions would we *not* have gotten through
> x86_64_start_kernel()?

xen will go with x86_64_start_reservations() directly.

Yinghai
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