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

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

[Jan Beulich]

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@novell.com>
Cc: Yinghai Lu <yhlu.kernel@gmail.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

[tip:x86/pat] x86: Fix earlyprintk=dbgp for machines without NX

[tip-bot for Jan Beulich]

Commit-ID:  47d25003cbd9e9030a95f7ccc4e70fec6aa7b844
Gitweb:     http://git.kernel.org/tip/47d25003cbd9e9030a95f7ccc4e70fec6aa7b844
Author:     Jan Beulich <JBeulich@novell.com>
AuthorDate: Fri, 28 Aug 2009 14:11:57 +0100
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Sat, 29 Aug 2009 15:47:32 +0200

x86: 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@novell.com>
Cc: Yinghai Lu <yhlu.kernel@gmail.com>
LKML-Reference: <4A97F3BD02000078000121B9@vpn.id2.novell.com>
[ merged to x86/pat to resolve a conflict. ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
 arch/x86/kernel/setup.c |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 02643cc..eb1f1e6 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -714,6 +714,16 @@ 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();
 
 	/* VMI may relocate the fixmap; do this before touching ioremap area */