Re: [PATCH] x86/mm/ident_map: Use full gbpages in identity maps except on UV platform.

[Ingo Molnar <mingo@kernel.org>]

* Steve Wahl <steve.wahl@hpe.com> wrote:

> Some systems have ACPI tables that don't include everything that needs
> to be mapped for a successful kexec.  These systems rely on identity
> maps that include the full gigabyte surrounding any smaller region
> requested for kexec success.  Without this, they fail to kexec and end
> up doing a full firmware reboot.
> 
> So, reduce the use of GB pages only on systems where this is known to
> be necessary (specifically, UV systems).
> 
> Signed-off-by: Steve Wahl <steve.wahl@hpe.com>
> Fixes: d794734c9bbf ("x86/mm/ident_map: Use gbpages only where full GB page should be mapped.")
> Reported-by: Pavin Joseph <me@pavinjoseph.com>

Sigh, why was d794734c9bbf marked for a -stable backport? The commit 
never explains ...

If it's broken, it should be reverted - instead of trying to partially 
revert and then maybe break some other systems.

When there's boot breakage with new patches, we back out the bad patch 
and re-try in 99.9% of the cases.

Thanks,

	Ingo