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

[Steve Wahl]

On Sun, Mar 24, 2024 at 11:31:39AM +0100, Ingo Molnar wrote:
> 
> * Steve Wahl <steve.wahl@xxxxxxx> 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@xxxxxxx>
> > Fixes: d794734c9bbf ("x86/mm/ident_map: Use gbpages only where full GB page should be mapped.")
> > Reported-by: Pavin Joseph <me@xxxxxxxxxxxxxxx>
> 
> 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.

Fine with me, especially as you've already done the revert. :-)

I will create a new patch that combines the two.  If you have any
specific actions you'd like to be sure I do for this, let me know.

Thanks,

--> Steve Wahl
-- 
Steve Wahl, Hewlett Packard Enterprise