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/20220910221947.171557773@xxxxxxxxxxxxx/ Suggested-by: Neeraj Upadhyay <quic_neeraju@xxxxxxxxxxx> Suggested-by: Frederic Weisbecker <frederic@xxxxxxxxxx> Suggested-by: Boqun Feng <boqun.feng@xxxxxxxxx> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx> Cc: Heiko Carstens <hca@xxxxxxxxxxxxx> Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx> Cc: Alexander Gordeev <agordeev@xxxxxxxxxxxxx> Cc: Christian Borntraeger <borntraeger@xxxxxxxxxxxxx> Cc: Sven Schnelle <svens@xxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: John Ogness <john.ogness@xxxxxxxxxxxxx> Cc: Petr Mladek <pmladek@xxxxxxxx> Cc: <linux-s390@xxxxxxxxxxxxxxx> --- arch/s390/Kconfig | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index 318fce77601d3..0acdfda332908 100644 --- a/arch/s390/Kconfig +++ b/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 -- 2.31.1.189.g2e36527f23
