Re: [PATCH v2] x86/efi: Correct ident mapping of efi old_map when kalsr enabled

From: Russ Anderson
Date: Sun May 07 2017 - 23:27:06 EST

On Sat, May 06, 2017 at 01:36:20AM +0200, Borislav Petkov wrote:
> On Fri, May 05, 2017 at 09:42:14PM +0100, Matt Fleming wrote:
> > (Including the folks from SGI since this was hit on a UV system)
> Wasn't there a BIOS fix supplied at some point which obviated the need
> to boot with efi=old_map on SGI boxes?

Yes, and other fixes to get new and old mapping working (except
for UV1 hardware). The kaslr patchset broke booting with old
mapping. That is the issue Baoquan, Bhupesh, and legacy SGI
engineers are trying to fix.

For those that want a more detailed summary:

In early 2014 upstream EFI changed the mapping, which lead to setting EFI_OLD_MEMMAP on all UV systems.

Later upstream fixes, plus a bios fix, got new mapping working.
Here are a couple of the fixes.

This patch enabled new EFI mapping on UV2+ platforms (all but UV1).
Note this is not bios version checking, it is hardware platform checking.

One of the fixes to get new map to work broke old map. This patch fixed it.

So upstream with recent bios works on UV2, UV3, and UV4 hardware platforms,
both old and new mapping, with new mapping being the default.

Russ Anderson, Hawks 2 Linux Kernel Group Manager
HPE - Hewlett Packard Enterprise (formerly SGI) rja@xxxxxxx (rja@xxxxxxx)