ACPI 5.0: Implement hardware-reduced option

If HW-reduced flag is set in the FADT, do not attempt to access
or initialize any ACPI hardware, including SCI and global lock.
No FACS will be present.

Signed-off-by: Bob Moore <robert.moore@xxxxxxxxx>

Also adjust acpi_fadt_parse_sleep_info().

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/acpi/boot.c
+++ b/xen/arch/x86/acpi/boot.c
@@ -328,6 +328,9 @@ acpi_fadt_parse_sleep_info(struct acpi_t
 	struct acpi_table_facs *facs = NULL;
 	uint64_t facs_pa;
 
+	if (fadt->flags & ACPI_FADT_HW_REDUCED)
+		goto bad;
+
 	acpi_fadt_copy_address(pm1a_cnt, pm1a_control, pm1_control);
 	acpi_fadt_copy_address(pm1b_cnt, pm1b_control, pm1_control);
 	acpi_fadt_copy_address(pm1a_evt, pm1a_event, pm1_event);
@@ -351,6 +354,8 @@ acpi_fadt_parse_sleep_info(struct acpi_t
 		       fadt->facs, facs_pa);
 		facs_pa = (uint64_t)fadt->facs;
 	}
+	if (!facs_pa)
+		goto bad;
 
 	facs = (struct acpi_table_facs *)
 		__acpi_map_table(facs_pa, sizeof(struct acpi_table_facs));
--- a/xen/include/acpi/acglobal.h
+++ b/xen/include/acpi/acglobal.h
@@ -78,6 +78,13 @@ ACPI_EXTERN struct acpi_table_fadt acpi_
 ACPI_EXTERN struct acpi_generic_address acpi_gbl_xpm1a_enable;
 ACPI_EXTERN struct acpi_generic_address acpi_gbl_xpm1b_enable;
 
+/*
+ * ACPI 5.0 introduces the concept of a "reduced hardware platform", meaning
+ * that the ACPI hardware is no longer required. A flag in the FADT indicates
+ * a reduced HW machine, and that flag is duplicated here for convenience.
+ */
+ACPI_EXTERN u8 acpi_gbl_reduced_hardware;
+
 /*****************************************************************************
  *
  * Miscellaneous globals
--- a/xen/drivers/acpi/tables/tbfadt.c
+++ b/xen/drivers/acpi/tables/tbfadt.c
@@ -197,8 +197,13 @@ void __init acpi_tb_parse_fadt(acpi_nati
 	acpi_tb_install_table((acpi_physical_address) acpi_gbl_FADT.Xdsdt,
 			      flags, ACPI_SIG_DSDT, ACPI_TABLE_INDEX_DSDT);
 
-	acpi_tb_install_table((acpi_physical_address) acpi_gbl_FADT.Xfacs,
-			      flags, ACPI_SIG_FACS, ACPI_TABLE_INDEX_FACS);
+	/* If Hardware Reduced flag is set, there is no FACS */
+
+	if (!acpi_gbl_reduced_hardware) {
+		acpi_tb_install_table((acpi_physical_address) acpi_gbl_FADT.
+				      Xfacs, flags, ACPI_SIG_FACS,
+				      ACPI_TABLE_INDEX_FACS);
+	}
 }
 
 /*******************************************************************************
@@ -242,6 +247,13 @@ void __init acpi_tb_create_local_fadt(st
 	ACPI_MEMCPY(&acpi_gbl_FADT, table,
 		    ACPI_MIN(length, sizeof(struct acpi_table_fadt)));
 
+	/* Take a copy of the Hardware Reduced flag */
+
+	acpi_gbl_reduced_hardware = FALSE;
+	if (acpi_gbl_FADT.flags & ACPI_FADT_HW_REDUCED) {
+		acpi_gbl_reduced_hardware = TRUE;
+	}
+
 	/*
 	 * 1) Convert the local copy of the FADT to the common internal format
 	 * 2) Validate some of the important values within the FADT
@@ -401,6 +413,12 @@ static void __init acpi_tb_validate_fadt
 	u8 length;
 	acpi_native_uint i;
 
+	/* If Hardware Reduced flag is set, we are all done */
+
+	if (acpi_gbl_reduced_hardware) {
+		return;
+	}
+
 	/* Examine all of the 64-bit extended address fields (X fields) */
 
 	for (i = 0; i < ACPI_FADT_INFO_ENTRIES; i++) {