x86, suspend: Restore MISC_ENABLE MSR in realmode wakeup
Some BIOSes will reset the Intel MISC_ENABLE MSR (specifically the
XD_DISABLE bit) when resuming from S3, which can interact poorly with
ebba638ae723d8a8fc2f7abce5ec18b688b791d7. In 32bit PAE mode, this can
lead to a fault when EFER is restored by the kernel wakeup routines,
due to it setting the NX bit for a CPU that (thanks to the BIOS reset)
now incorrectly thinks it lacks the NX feature. (64bit is not affected
because it uses a common CPU bring-up that specifically handles the
XD_DISABLE bit.)
The need for MISC_ENABLE being restored so early is specific to the S3
resume path. Normally, MISC_ENABLE is saved in save_processor_state(),
but this happens after the resume header is created, so just reproduce
the logic here. (acpi_suspend_lowlevel() creates the header, calls
do_suspend_lowlevel, which calls save_processor_state(), so the saved
processor context isn't available during resume header creation.)
[ hpa: Consider for stable if OK in mainline ]
Signed-off-by: Kees Cook <kees.cook@canonical.com>
Link: http://lkml.kernel.org/r/20110707011034.GA8523@outflux.net
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Rafael J. Wysocki <rjw@sisk.pl>
Cc: <stable@kernel.org> 2.6.38+
diff --git a/arch/x86/kernel/acpi/sleep.c b/arch/x86/kernel/acpi/sleep.c
index 18a857b..103b6ab 100644
--- a/arch/x86/kernel/acpi/sleep.c
+++ b/arch/x86/kernel/acpi/sleep.c
@@ -77,6 +77,12 @@
header->pmode_cr0 = read_cr0();
header->pmode_cr4 = read_cr4_safe();
+ header->pmode_behavior = 0;
+ if (!rdmsr_safe(MSR_IA32_MISC_ENABLE,
+ &header->pmode_misc_en_low,
+ &header->pmode_misc_en_high))
+ header->pmode_behavior |=
+ (1 << WAKEUP_BEHAVIOR_RESTORE_MISC_ENABLE);
header->realmode_flags = acpi_realmode_flags;
header->real_magic = 0x12345678;