Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> writes: > From: Nicholas Piggin <npiggin@xxxxxxxxx> > > [ 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@xxxxxxxxx> > Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx> > Link: https://lore.kernel.org/r/20200914045219.3736466-3-npiggin@xxxxxxxxx > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> > --- > 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
