| Message ID | 20210915190336.398390-1-pcc@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v3,1/2] arm64: add an MTE support check to the top of mte_thread_switch() | expand |
On Wed, 15 Sep 2021 12:03:35 -0700, Peter Collingbourne wrote: > This lets us avoid doing unnecessary work on hardware that does > not support MTE, and will allow us to freely use MTE instructions > in the code called by mte_thread_switch(). > > Since this would mean that we do a redundant check in > mte_check_tfsr_el1(), remove it and add two checks now required in > its callers. I applied the first patch to arm64 (for-next/fixes), it should appear in 5.15-rc3. It looks to me more like a performance regression with the additional dsb+isb on the syscall path for hw not supporting MTE (and I added a Fixes tag). I'll leave the second patch to Will for 5.16. Thanks! [1/2] arm64: add an MTE support check to the top of mte_thread_switch() https://git.kernel.org/arm64/c/8c8a3b5bd960
diff --git a/arch/arm64/include/asm/mte.h b/arch/arm64/include/asm/mte.h index 3f93b9e0b339..02511650cffe 100644 --- a/arch/arm64/include/asm/mte.h +++ b/arch/arm64/include/asm/mte.h @@ -99,11 +99,17 @@ void mte_check_tfsr_el1(void); static inline void mte_check_tfsr_entry(void) { + if (!system_supports_mte()) + return; + mte_check_tfsr_el1(); } static inline void mte_check_tfsr_exit(void) { + if (!system_supports_mte()) + return; + /* * The asynchronous faults are sync'ed automatically with * TFSR_EL1 on kernel entry but for exit an explicit dsb() diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c index 9d314a3bad3b..e5e801bc5312 100644 --- a/arch/arm64/kernel/mte.c +++ b/arch/arm64/kernel/mte.c @@ -142,12 +142,7 @@ void mte_enable_kernel_async(void) #ifdef CONFIG_KASAN_HW_TAGS void mte_check_tfsr_el1(void) { - u64 tfsr_el1; - - if (!system_supports_mte()) - return; - - tfsr_el1 = read_sysreg_s(SYS_TFSR_EL1); + u64 tfsr_el1 = read_sysreg_s(SYS_TFSR_EL1); if (unlikely(tfsr_el1 & SYS_TFSR_EL1_TF1)) { /* @@ -199,6 +194,9 @@ void mte_thread_init_user(void) void mte_thread_switch(struct task_struct *next) { + if (!system_supports_mte()) + return; + mte_update_sctlr_user(next); /*
This lets us avoid doing unnecessary work on hardware that does not support MTE, and will allow us to freely use MTE instructions in the code called by mte_thread_switch(). Since this would mean that we do a redundant check in mte_check_tfsr_el1(), remove it and add two checks now required in its callers. Signed-off-by: Peter Collingbourne <pcc@google.com> Link: https://linux-review.googlesource.com/id/I02fd000d1ef2c86c7d2952a7f099b254ec227a5d --- v3: - remove check from mte_check_tfsr_el1() arch/arm64/include/asm/mte.h | 6 ++++++ arch/arm64/kernel/mte.c | 10 ++++------ 2 files changed, 10 insertions(+), 6 deletions(-)