[ 07/21] x86: Fix bit corruption at CPU resume time

From: Greg Kroah-Hartman
Date: Wed May 22 2013 - 18:10:52 EST

3.9-stable review patch. If anyone has any objections, please let me know.


From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>

commit 5e427ec2d066b48a5c27b3a5a3315f7e4e729077 upstream.

In commit 78d77df71510 ("x86-64, init: Do not set NX bits on non-NX
capable hardware") we added the early_pmd_flags that gets the NX bit set
when a CPU supports NX. However, the new variable was marked __initdata,
because the main _use_ of this is in an __init routine.

However, the bit setting happens from secondary_startup_64(), which is
called not only at bootup, but on every secondary CPU start. Including
resuming from STR and at CPU hotplug time. So the value cannot be

Reported-bisected-and-tested-by: Michal Hocko <mhocko@xxxxxxx>
Acked-by: Peter Anvin <hpa@xxxxxxxxxxxxxxx>
Cc: Fernando Luis VÃzquez Cao <fernando@xxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

arch/x86/kernel/head64.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -34,7 +34,7 @@
extern pgd_t early_level4_pgt[PTRS_PER_PGD];
extern pmd_t early_dynamic_pgts[EARLY_DYNAMIC_PAGE_TABLES][PTRS_PER_PMD];
static unsigned int __initdata next_early_pgt = 2;
-pmdval_t __initdata early_pmd_flags = __PAGE_KERNEL_LARGE & ~(_PAGE_GLOBAL | _PAGE_NX);
+pmdval_t early_pmd_flags = __PAGE_KERNEL_LARGE & ~(_PAGE_GLOBAL | _PAGE_NX);

/* Wipe all early page tables except for the kernel symbol map */
static void __init reset_early_page_tables(void)

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