The patch below does not apply to the 5.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable@xxxxxxxxxxxxxxx>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 8c8a3b5bd960cd88f7655b5251dc28741e11f139 Mon Sep 17 00:00:00 2001 From: Peter Collingbourne <pcc@xxxxxxxxxx> Date: Wed, 15 Sep 2021 12:03:35 -0700 Subject: [PATCH] arm64: add MTE supported check to thread switching and syscall entry/exit 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. This also avoids an unnecessary DSB+ISB sequence on the syscall exit path for hardware not supporting MTE. Fixes: 65812c6921cc ("arm64: mte: Enable async tag check fault") Cc: <stable@xxxxxxxxxxxxxxx> # 5.13.x Signed-off-by: Peter Collingbourne <pcc@xxxxxxxxxx> Link: https://linux-review.googlesource.com/id/I02fd000d1ef2c86c7d2952a7f099b254ec227a5d Link: https://lore.kernel.org/r/20210915190336.398390-1-pcc@xxxxxxxxxx [catalin.marinas@xxxxxxx: adjust the commit log slightly] Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx> 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); /*