linux-kernel - Re: linux-next: reservetop fix disables mem=

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Date:	Mon, 24 Aug 2009 20:27:13 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Zachary Amsden <zach@...are.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Xiao Guangrong <xiaooguangrong@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: linux-next: reservetop fix disables mem=


* Yinghai Lu <yinghai@...nel.org> wrote:

> Hugh Dickins wrote:
> > I find the "mem=" boot parameter disabled in today's linux-next:
> > reverting the tip commit below fixes that.
> > 
> > Hugh
> > 
> > From: Xiao Guangrong <xiaoguangrong@...fujitsu.com>
> > Date: Thu, 20 Aug 2009 12:23:11 +0000 (+0800)
> > Subject: x86: Fix system crash when loading with "reservetop" parameter
> > X-Git-Url: http://git.kernel.org/?p=linux%2Fkernel%2Fgit%2Fmingo%2Flinux-2.6-x86.git;a=commitdiff_plain;h=8126dec32738421afa362114337331337b4be17f
> > 
> > x86: Fix system crash when loading with "reservetop" parameter
> > 
> > The system will die if the kernel is booted with "reservetop"
> > parameter, in present code, parse "reservetop" parameter after
> > early_ioremap_init(), and some function still use
> > early_ioremap() after it.
> > 
> > The problem is, "reservetop" parameter can modify
> > 'FIXADDR_TOP', then the virtual address got by early_ioremap()
> > is base on old 'FIXADDR_TOP', but the page mapping is base on
> > new 'FIXADDR_TOP', it will occur page fault, and the IDT is not
> > prepare yet, so, the system is dead.
> > 
> > So, put parse_early_param() in the front of
> > early_ioremap_init() in this patch.
> > 
> > Signed-off-by: Xiao Guangrong <xiaoguangrong@...fujitsu.com>
> > Cc: yinghai@...nel.org
> > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > LKML-Reference: <4A8D402F.4080805@...fujitsu.com>
> > Signed-off-by: Ingo Molnar <mingo@...e.hu>
> > ---
> > 
> > diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> > index 63f32d2..02643cc 100644
> > --- a/arch/x86/kernel/setup.c
> > +++ b/arch/x86/kernel/setup.c
> > @@ -711,6 +711,11 @@ void __init setup_arch(char **cmdline_p)
> >  	printk(KERN_INFO "Command line: %s\n", boot_command_line);
> >  #endif
> >  
> > +	strlcpy(command_line, boot_command_line, COMMAND_LINE_SIZE);
> > +	*cmdline_p = command_line;
> > +
> > +	parse_early_param();
> > +
> >  	/* VMI may relocate the fixmap; do this before touching ioremap area */
> >  	vmi_init();
> >  
> > @@ -793,11 +798,6 @@ void __init setup_arch(char **cmdline_p)
> >  #endif
> >  #endif
> >  
> > -	strlcpy(command_line, boot_command_line, COMMAND_LINE_SIZE);
> > -	*cmdline_p = command_line;
> > -
> > -	parse_early_param();
> > -
> >  #ifdef CONFIG_X86_64
> >  	check_efer();
> >  #endif
> 
> yes, that patch will break other built-in command too.
> 
> need drop that patch.

done. Was nervous about the patch already:

  http://lkml.org/lkml/2009/8/21/127

> also the problem was caused by vmi patch, and that commit should 
> be reverted.
>
> commit ae8d04e2ecbb233926860e9ce145eac19c7835dc
> Author: Zachary Amsden <zach@...are.com>
> Date:   Sat Dec 13 12:36:58 2008 -0800
> 
>     x86 Fix VMI crash on boot in 2.6.28-rc8
>     
>     VMI initialiation can relocate the fixmap, causing early_ioremap to
>     malfunction if it is initialized before the relocation.  To fix this,
>     VMI activation is split into two phases; the detection, which must
>     happen before setting up ioremap, and the activation, which must happen
>     after parsing early boot parameters.
>     
>     This fixes a crash on boot when VMI is enabled under VMware.
>     
>     Signed-off-by: Zachary Amsden <zach@...are.com>
>     Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
> 
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index 9d5674f..bdec76e 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -794,6 +794,9 @@ void __init setup_arch(char **cmdline_p)
>         printk(KERN_INFO "Command line: %s\n", boot_command_line);
>  #endif
>  
> +       /* VMI may relocate the fixmap; do this before touching ioremap area */
> +       vmi_init();
> +
>         early_cpu_init();
>         early_ioremap_init();
>  
> @@ -880,13 +883,8 @@ void __init setup_arch(char **cmdline_p)
>         check_efer();
>  #endif
>  
> -#if defined(CONFIG_VMI) && defined(CONFIG_X86_32)
> -       /*
> -        * Must be before kernel pagetables are setup
> -        * or fixmap area is touched.
> -        */
> -       vmi_init();
> -#endif
> +       /* Must be before kernel pagetables are setup */
> +       vmi_activate();
>  
>         /* after early param, so could get panic from serial */
>         reserve_early_setup_data();
> 
> 
> and according to
> http://lkml.org/lkml/2008/12/10/388
> http://lkml.org/lkml/2008/12/10/456
> 
> Zachary should split reserve_top_address() to two functions... 
> before sending that patch to Linus

mind looking at this yourself if interested? Zachary has not been 
active for quite some time.

	Ingo
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