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Updates for Powerpc kexec

Mamatha Inamdar requested to merge mainamdar/centos-stream-9:RHEL-14159 into main

Description: Updates for Powerpc kexec

JIRA: https://issues.redhat.com/browse/RHEL-14159

Build Info: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=62861128

Tested: Verified Brew build test kernel RPMs and confirmed issue is resovled

Signed-off-by: Mamatha Inamdar minamdar@redhat.com

commit 21a741eb75f80397e5f7d3739e24d7d75e619011 Author: Nicholas Piggin npiggin@gmail.com Date: Tue Jun 25 23:40:47 2024 +1000

powerpc/pseries: Fix scv instruction crash with kexec

kexec on pseries disables AIL (reloc_on_exc), required for scv
instruction support, before other CPUs have been shut down. This means
they can execute scv instructions after AIL is disabled, which causes an
interrupt at an unexpected entry location that crashes the kernel.

Change the kexec sequence to disable AIL after other CPUs have been
brought down.

As a refresher, the real-mode scv interrupt vector is 0x17000, and the
fixed-location head code probably couldn't easily deal with implementing
such high addresses so it was just decided not to support that interrupt
at all.

Fixes: 7fa95f9adaee ("powerpc/64s: system call support for scv/rfscv instructions")
Cc: stable@vger.kernel.org # v5.9+
Reported-by: Sourabh Jain <sourabhjain@linux.ibm.com>
Closes: https://lore.kernel.org/3b4b2943-49ad-4619-b195-bc416f1d1409@linux.ibm.com
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Tested-by: Gautam Menghani <gautam@linux.ibm.com>
Tested-by: Sourabh Jain <sourabhjain@linux.ibm.com>
Link: https://msgid.link/20240625134047.298759-1-npiggin@gmail.com
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Signed-off-by: Mamatha Inamdar minamdar@redhat.com

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