linux-kernel - [PATCH] x86-64: fix earlyprintk=dbgp for machines without NX

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Date:	Fri, 28 Aug 2009 14:11:57 +0100
From:	"Jan Beulich" <JBeulich@...ell.com>
To:	<mingo@...e.hu>, <tglx@...utronix.de>, <hpa@...or.com>
Cc:	<yhlu.kernel@...il.com>, <linux-kernel@...r.kernel.org>
Subject: [PATCH] x86-64: fix earlyprintk=dbgp for machines without NX

Since parse_early_param() may (e.g. for earlyprintk=dbgp) involve calls
to page table manipulation functions (here set_fixmap_nocache()), NX
hardware support must be determined before calling that function (so
that __supported_pte_mask gets properly set up). But the call after
parse_early_param() can also not go away, as that will honor eventual
command line specified disabling of the NX functionality (this will
then just result in whatever mappings got established during
parse_early_param() having the NX bit set despite it being disabled on
the command line, but I think that's tolerable).

Signed-off-by: Jan Beulich <jbeulich@...ell.com>
Cc: Yinghai Lu <yhlu.kernel@...il.com>

---
 arch/x86/kernel/setup.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

--- linux-2.6.31-rc8/arch/x86/kernel/setup.c	2009-08-28 14:57:38.000000000 +0200
+++ 2.6.31-rc8-x86_64-check-efer-earlier/arch/x86/kernel/setup.c	2009-08-28 14:52:33.000000000 +0200
@@ -796,6 +796,16 @@ void __init setup_arch(char **cmdline_p)
 	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



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