powerpc: select ARCH_WANT_IRQS_OFF_ACTIVATE_MM

powerpc uses IPIs in some situations to switch a kernel thread away
from a lazy tlb mm, which is subject to the TLB flushing race
described in the changelog introducing ARCH_WANT_IRQS_OFF_ACTIVATE_MM.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200914045219.3736466-3-npiggin@gmail.com

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 1f48bbf..65cb322 100644 (file)
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -149,6 +149,7 @@ config PPC
        select ARCH_USE_QUEUED_RWLOCKS          if PPC_QUEUED_SPINLOCKS
        select ARCH_USE_QUEUED_SPINLOCKS        if PPC_QUEUED_SPINLOCKS
        select ARCH_WANT_IPC_PARSE_VERSION
+       select ARCH_WANT_IRQS_OFF_ACTIVATE_MM
        select ARCH_WEAK_RELEASE_ACQUIRE
        select BINFMT_ELF
        select BUILDTIME_TABLE_SORT

diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h
index 7f3658a..e02aa79 100644 (file)
--- a/arch/powerpc/include/asm/mmu_context.h
+++ b/arch/powerpc/include/asm/mmu_context.h
@@ -244,7 +244,7 @@ static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
  */
 static inline void activate_mm(struct mm_struct *prev, struct mm_struct *next)
 {
-       switch_mm(prev, next, current);
+       switch_mm_irqs_off(prev, next, current);
 }
 
 /* We don't currently use enter_lazy_tlb() for anything */