diff --git a/drivers/acpi/acpica/hwvalid.c b/drivers/acpi/acpica/hwvalid.c
index 915b26448d2c..0d392e7b0747 100644
--- a/drivers/acpi/acpica/hwvalid.c
+++ b/drivers/acpi/acpica/hwvalid.c
@@ -23,8 +23,8 @@ acpi_hw_validate_io_request(acpi_io_address address, u32 bit_width);
  *
  * The table is used to implement the Microsoft port access rules that
  * first appeared in Windows XP. Some ports are always illegal, and some
- * ports are only illegal if the BIOS calls _OSI with a win_XP string or
- * later (meaning that the BIOS itelf is post-XP.)
+ * ports are only illegal if the BIOS calls _OSI with nothing newer than
+ * the specific _OSI strings.
  *
  * This provides ACPICA with the desired port protections and
  * Microsoft compatibility.
@@ -145,7 +145,8 @@ acpi_hw_validate_io_request(acpi_io_address address, u32 bit_width)
 
 			/* Port illegality may depend on the _OSI calls made by the BIOS */
 
-			if (acpi_gbl_osi_data >= port_info->osi_dependency) {
+			if (port_info->osi_dependency == ACPI_ALWAYS_ILLEGAL ||
+			    acpi_gbl_osi_data == port_info->osi_dependency) {
 				ACPI_DEBUG_PRINT((ACPI_DB_VALUES,
 						  "Denied AML access to port 0x%8.8X%8.8X/%X (%s 0x%.4X-0x%.4X)\n",
 						  ACPI_FORMAT_UINT64(address),