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

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Date:	Mon, 11 Oct 2010 11:37:39 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Yinghai Lu <yinghai@...nel.org>
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 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()?

	-hpa
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