-stable review patch. If anyone has any objections, please let us know.
---------------------
From: Len Brown <[email protected]>
Up through 2.6.20 we cleared the FADT.CSTATE_CONTROL field
for FADT versions before r3, because it made no sense
for that reserved field to be set for pre-ACPI 2.0 systems.
It turns out that not clearing this field exposes
Linux to SMM BIOS failures, so do the same in 2.6.21.
http://bugzilla.kernel.org/show_bug.cgi?id=8346
Signed-off-by: Len Brown <[email protected]>
Signed-off-by: Chris Wright <[email protected]>
---
drivers/acpi/tables/tbfadt.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
--- linux-2.6.21.1.orig/drivers/acpi/tables/tbfadt.c
+++ linux-2.6.21.1/drivers/acpi/tables/tbfadt.c
@@ -347,6 +347,20 @@ static void acpi_tb_convert_fadt(void)
acpi_gbl_xpm1b_enable.space_id = acpi_gbl_FADT.xpm1a_event_block.space_id;
}
+ /*
+ * _CST object and C States change notification start with
+ * ACPI 2.0 (FADT r3). Although the field should be Reserved
+ * and 0 before then, some pre-r3 FADT set this field and
+ * it results in SMM-related boot failures. For them, clear it.
+ */
+ if ((acpi_gbl_FADT.header.revision < 3) &&
+ (acpi_gbl_FADT.cst_control != 0)) {
+ ACPI_WARNING((AE_INFO,
+ "Ignoring BIOS FADT r%u C-state control",
+ acpi_gbl_FADT.header.revision));
+ acpi_gbl_FADT.cst_control = 0;
+ }
+
}
/******************************************************************************
--