On Tue, Jan 26, 2021 at 4:50 AM Will Deacon <will@xxxxxxxxxx> wrote: > > On Tue, Dec 29, 2020 at 10:59:13PM -0800, Peter Collingbourne wrote: > > In an upcoming change we are going to introduce per-task SCTLR_EL1 > > bits for PAC. Move the existing per-task SCTLR_EL1 field out of the > > MTE-specific code so that we will be able to use it from both the > > PAC and MTE code paths and make the task switching code more efficient. > > > > Signed-off-by: Peter Collingbourne <pcc@xxxxxxxxxx> > > Link: https://linux-review.googlesource.com/id/Ic65fac78a7926168fa68f9e8da591c9e04ff7278 > > --- > > arch/arm64/Kconfig | 4 +++ > > arch/arm64/include/asm/mte.h | 4 --- > > arch/arm64/include/asm/processor.h | 10 ++++++- > > arch/arm64/kernel/mte.c | 47 ++++++------------------------ > > arch/arm64/kernel/process.c | 34 +++++++++++++++++---- > > 5 files changed, 50 insertions(+), 49 deletions(-) > > > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > > index 05e17351e4f3..82e38d1ca012 100644 > > --- a/arch/arm64/Kconfig > > +++ b/arch/arm64/Kconfig > > @@ -348,6 +348,9 @@ config KASAN_SHADOW_OFFSET > > default 0xeffffff800000000 if ARM64_VA_BITS_36 && KASAN_SW_TAGS > > default 0xffffffffffffffff > > > > +config ARM64_NEED_SCTLR_USER > > + bool > > + > > source "arch/arm64/Kconfig.platforms" > > > > menu "Kernel Features" > > @@ -1653,6 +1656,7 @@ config ARM64_MTE > > # Required for tag checking in the uaccess routines > > depends on ARM64_PAN > > select ARCH_USES_HIGH_VMA_FLAGS > > + select ARM64_NEED_SCTLR_USER > > I'm not sure I'd bother with this; is it the end of the world if we do this > unconditionally? I think I'd be fine with doing it unconditionally. If both PAC and MTE are disabled then I believe that the only additional code that we would end up executing is the comparison between prev and next sctlr_user on task switch in process.c (which would always yield false) and since task switch is much less common than entry/exit it seems acceptable to me. Peter
