arch/s390: Add ARCH_HAS_NMI_SAFE_THIS_CPU_OPS Kconfig option

The s390 architecture uses either a cmpxchg loop (old systems)
or the laa add-to-memory instruction (new systems) to implement
this_cpu_add(), both of which are NMI safe.  This means that the old
and more-efficient srcu_read_lock() may be used in NMI context, without
the need for srcu_read_lock_nmisafe().  Therefore, add the new Kconfig
option ARCH_HAS_NMI_SAFE_THIS_CPU_OPS to arch/arm64/Kconfig, which will
cause NEED_SRCU_NMI_SAFE to be deselected, thus preserving the current
srcu_read_lock() behavior.

Link: https://lore.kernel.org/all/[email protected]/

Suggested-by: Neeraj Upadhyay <[email protected]>
Suggested-by: Frederic Weisbecker <[email protected]>
Suggested-by: Boqun Feng <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Vasily Gorbik <[email protected]>
Cc: Alexander Gordeev <[email protected]>
Cc: Christian Borntraeger <[email protected]>
Cc: Sven Schnelle <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: John Ogness <[email protected]>
Cc: Petr Mladek <[email protected]>
Cc: <[email protected]>

Author: paulmckrcu

arch/s390/Kconfig

@@ -73,6 +73,7 @@ config S390
 	select ARCH_HAS_GIGANTIC_PAGE
 	select ARCH_HAS_KCOV
 	select ARCH_HAS_MEM_ENCRYPT
+	select ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
 	select ARCH_HAS_PTE_SPECIAL
 	select ARCH_HAS_SCALED_CPUTIME
 	select ARCH_HAS_SET_MEMORY