Re: linux-next: reservetop fix disables mem=

[Yinghai Lu <yinghai@kernel.org>]

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@cn.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@cn.fujitsu.com>
> Cc: yinghai@kernel.org
> Cc: Andrew Morton <akpm@linux-foundation.org>
> LKML-Reference: <4A8D402F.4080805@cn.fujitsu.com>
> Signed-off-by: Ingo Molnar <mingo@elte.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.

also the problem was caused by vmi patch, and that commit should be reverted.

commit ae8d04e2ecbb233926860e9ce145eac19c7835dc
Author: Zachary Amsden <zach@vmware.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@vmware.com>
    Signed-off-by: Linus Torvalds <torvalds@linux-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


YH