Greg Kroah-Hartman gregkh@linuxfoundation.org writes:
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 f38d153d25861..0bc53f0e37c0f 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -152,6 +152,7 @@ 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
This depends on upstream commit:
d53c3dfb23c4 ("mm: fix exec activate_mm vs TLB shootdown and lazy tlb switching race")
Which I don't see in 4.19 stable, or in the email thread here.
So this shouldn't be backported to 4.19 unless that commit is also backported.
cheers