arch/x86: Add ARCH_HAS_NMI_SAFE_THIS_CPU_OPS Kconfig option

The x86 architecture uses an add-to-memory instruction to implement
this_cpu_add(), which is 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/x86/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@linutronix.de/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Petr Mladek <pmladek@suse.com>
Cc: <x86@kernel.org>

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 6d1879ef933a2c129ad05d2f7c3254b0347c2e38..bcb3190eaa266a08f6ad587eec6c4cf211dd741f 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -81,6 +81,7 @@ config X86
        select ARCH_HAS_KCOV                    if X86_64
        select ARCH_HAS_MEM_ENCRYPT
        select ARCH_HAS_MEMBARRIER_SYNC_CORE
+       select ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
        select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
        select ARCH_HAS_PMEM_API                if X86_64
        select ARCH_HAS_PTE_DEVMAP              if X86_64