[PATCH AUTOSEL 5.8 006/132] powerpc: select ARCH_WANT_IRQS_OFF_ACTIVATE_MM

Sasha Levin
2020-10-27T00:34:28Z

From: Nicholas Piggin <npiggin@gmail.com>

[ Upstream commit 66acd46080bd9e5ad2be4b0eb1d498d5145d058e ]

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
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/powerpc/Kconfig | 1 +
arch/powerpc/include/asm/mmu_context.h | 2 +-
2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 9fa23eb320ff5..1692c9def44c9 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -146,6 +146,7 @@ config PPC
select ARCH_USE_BUILTIN_BSWAP
select ARCH_USE_CMPXCHG_LOCKREF if PPC64
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 1a474f6b1992a..6cb10c7a52025 100644
--- a/arch/powerpc/include/asm/mmu_context.h
+++ b/arch/powerpc/include/asm/mmu_context.h
@@ -246,7 +246,7 @@ 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 */
--
2.25.1