On 02/01/17 13:52, Laszlo Ersek wrote: > On 02/01/17 12:37, Igor Mammedov wrote: >> On Tue, 31 Jan 2017 20:17:02 +0200 >> "Michael S. Tsirkin" <m...@redhat.com> wrote: >> >>> On Tue, Jan 31, 2017 at 05:28:57PM +0100, Laszlo Ersek wrote: >>>> The ACPI 6.1 spec says, >>>> >>>> - DSDT: [...] If the X_DSDT field contains a non-zero value then this >>>> field must be zero. >>>> - X_DSDT: [...] If the DSDT field contains a non-zero value then this >>>> field must be zero. >>> >>> But that's only 6.1. 6.0 and earlier did not say this. >>> The errata they wanted to address was: >>> 1393 In FADT: if X_DSDT field is non-zero, DSDT >>> field should be ignored or deprecated >>> >>> I would class this as a spec bug. >>> >> >> The same applies to X_PM1a_EVT_BLK and co, >> for example 5.1 spec "This is a required >> field." >> >> And looks like Windows implemented it as mandatory >> to boot perhaps to be compatible with 5.1 and earlier >> specs. >> >> It appears fw would be forced to fill fields depending >> on table revision. > > Sounds like a valid point. > > I compared the FADT defintion between ACPI 5.1 and ACPI 6.1. Indeed, the > former says: > > - FADT Major Version: 5; Major Version of this FADT structure, [...] > - DSDT: Physical memory address (0-4 GB) of the DSDT. > - X_DSDT: 64bit physical address of the DSDT. > > the latter says: > > - FADT Major Version: 6; Major Version of this FADT structure, [...] > > - DSDT: Physical memory address of the DSDT. If the X_DSDT field > contains a non-zero value then this field must be zero. > > - X_DSDT: Extended physical address of the DSDT. If the DSDT field > contains a non-zero value then this field must be zero. > > I will ask on edk2-devel whether the > "MdeModulePkg/Universal/Acpi/AcpiTableDxe" maintainers can think of a > way to accommodate this.
Sigh, this looks nasty. Considering specifically the DSDT <-> X_DSDT question, Mantis ticket #1393 (which requires the mutual exclusion) went into 5.1B. In version 5.1A, the mutual exclusion is not required. Unfortuantely, the FADT Major.Minor version, as reported through the bytes at offsets 8 and 131 decimal in the table, is "5.1" for *both* 5.1A and 5.1B. In other words, looking at just Major.Minor, it cannot be determined with full precision whether the DSDT and X_DSDT fields should be exclusive or not. :/ Laszlo
