tree 31f52293a54d418ff347e7de20ffc702acf554be
parent 88dff4936c0a5fa53080cca68dc963a8a2a674b0
author H. Peter Anvin <hpa@zytor.com> 1242931576 -0700
committer H. Peter Anvin <hpa@zytor.com> 1243016042 -0700

x86, setup: revert ACPI 3 E820 extended attributes support

Remove ACPI 3 E820 extended memory attributes support.  At least one
vendor actively set all the flags to zero, but left ECX on return at
24.  This bug may be present in other BIOSes.

The breakage functionally means the ACPI 3 flags are probably
completely useless, and that no OS any time soon is going to rely on
their existence.  Therefore, drop support completely.  We may want to
revisit this question in the future, if we find ourselves actually
needing the flags.

This reverts all or part of the following checkins:

     cd670599b7b00d9263f6f11a05c0edeb9cbedaf3
     c549e71d073a6e9a4847497344db28a784061455

However, retain the part from the latter commit that copies e820 into
a temporary buffer; that is an unrelated BIOS workaround.  Put in a
comment to explain that part.

See https://bugzilla.redhat.com/show_bug.cgi?id=499396 for some
additional information.

[ Impact: detect all memory on affected machines ]

Reported-by: Thomas J. Baker <tjb@unh.edu>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Acked-by: Len Brown <len.brown@intel.com>
Cc: Chuck Ebbert <cebbert@redhat.com>
Cc: Kyle McMartin <kmcmartin@redhat.com>
Cc: Matt Domsch <matt_domsch@dell.com>