On Tue, Nov 17, 2020 at 10:51:16AM -0800, Kamal Mostafa wrote:
On Tue, Nov 3, 2020 at 4:22 PM Michael Ellerman <mpe@xxxxxxxxxxxxxx> wrote:
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
Hi-
This glitch has made its way into 4.14.y ...
[4.14.y] c2bca8712a19 powerpc: select ARCH_WANT_IRQS_OFF_ACTIVATE_MM
But 4.14.y does not carry the prereq that introduces that config.
I'll queue up the 4.19 backport for 4.14 too, thanks!
--
Thanks,
Sasha
