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

From: Jan Beulich
Date: Fri Aug 28 2009 - 09:12:02 EST

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@xxxxxxxxxx>
Cc: Yinghai Lu <yhlu.kernel@xxxxxxxxx>

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();

#ifdef CONFIG_X86_64

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