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 <len.brown@xxxxxxxxx> --- diff --git a/drivers/acpi/tables/tbfadt.c b/drivers/acpi/tables/tbfadt.c index 807c711..d341491 100644 --- a/drivers/acpi/tables/tbfadt.c +++ b/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; + } + } /****************************************************************************** - To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
