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

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Date:	Sat, 19 Sep 2009 11:07:57 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: linux-next: reservetop fix disables mem=

Yinghai Lu wrote:
> Ingo Molnar wrote:
>> I thoroughly zapped it. Do you know about any commit ID where it snuck 
>> in?
> 
> after close looking, it will break
> 1. some cpu feature  in early stage too, like cpu_has_x2apic
> 2. will break built-in-command line
> 3. will break other memmap= and mem=
> 4. early_dbgp and early_console that will use early_ioremap to access mmio (?)
> 
> YH
> 
> commit 8126dec32738421afa362114337331337b4be17f
> Author: Xiao Guangrong <xiaoguangrong@...fujitsu.com>
> Date:   Thu Aug 20 20:23:11 2009 +0800
> 
>     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>
> 
after revet it, it seem mem=32g etc still broken, maybe some other commit about x86 platform support from Thomas broke it.

YH

---
 arch/x86/kernel/setup.c |   30 +++++++++++++++---------------
 1 file changed, 15 insertions(+), 15 deletions(-)

Index: linux-2.6/arch/x86/kernel/setup.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/setup.c
+++ linux-2.6/arch/x86/kernel/setup.c
@@ -697,21 +697,6 @@ 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;
-
-#ifdef CONFIG_X86_64
-	/*
-	 * Must call this twice: Once just to detect whether hardware doesn't
-	 * support NX (so that the early EHCI debug console setup can safely
-	 * call set_fixmap(), and then again after parsing early parameters to
-	 * honor the respective command line option.
-	 */
-	check_efer();
-#endif
-
-	parse_early_param();
-
 	/* VMI may relocate the fixmap; do this before touching ioremap area */
 	vmi_init();
 
@@ -794,6 +779,21 @@ void __init setup_arch(char **cmdline_p)
 #endif
 #endif
 
+	strlcpy(command_line, boot_command_line, COMMAND_LINE_SIZE);
+	*cmdline_p = command_line;
+
+#ifdef CONFIG_X86_64
+	/*
+	 * Must call this twice: Once just to detect whether hardware doesn't
+	 * support NX (so that the early EHCI debug console setup can safely
+	 * call set_fixmap(), and then again after parsing early parameters to
+	 * honor the respective command line option.
+	 */
+	check_efer();
+#endif
+
+	parse_early_param();
+
 #ifdef CONFIG_X86_64
 	check_efer();
 #endif
--
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