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| author |   Peter Collingbourne <pcc@google.com> | 2022-02-18 17:29:45 -0800 |
|---|---|---|
| committer |   Will Deacon <will@kernel.org> | 2022-02-22 21:48:44 +0000 |
| commit | 38ddf7dafaeaf3fcdea65b3b4dfb06b4bcd9cc15 (patch) | |
| tree | c147e82d6955532fdb6e42e7d23757374f3cce25 /arch/arm64/kernel/entry.S | |
| parent | kasan: split kasan_*enabled() functions into a separate header (diff) | |
| download | linux-dev-38ddf7dafaeaf3fcdea65b3b4dfb06b4bcd9cc15.tar.xz linux-dev-38ddf7dafaeaf3fcdea65b3b4dfb06b4bcd9cc15.zip | |
arm64: mte: avoid clearing PSTATE.TCO on entry unless necessary
On some microarchitectures, clearing PSTATE.TCO is expensive. Clearing
TCO is only necessary if in-kernel MTE is enabled, or if MTE is
enabled in the userspace process in synchronous (or, soon, asymmetric)
mode, because we do not report uaccess faults to userspace in none
or asynchronous modes. Therefore, adjust the kernel entry code to
clear TCO only if necessary.
Because it is now possible to switch to a task in which TCO needs to
be clear from a task in which TCO is set, we also need to do the same
thing on task switch.
Signed-off-by: Peter Collingbourne <pcc@google.com>
Link: https://linux-review.googlesource.com/id/I52d82a580bd0500d420be501af2c35fa8c90729e
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20220219012945.894950-2-pcc@google.com
Signed-off-by: Will Deacon <will@kernel.org>
Diffstat (limited to 'arch/arm64/kernel/entry.S')
| -rw-r--r-- | arch/arm64/kernel/entry.S | 7 |
1 files changed, 0 insertions, 7 deletions
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 772ec2ecf488..e1013a83d4f0 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -308,13 +308,6 @@ alternative_if ARM64_HAS_IRQ_PRIO_MASKING msr_s SYS_ICC_PMR_EL1, x20 alternative_else_nop_endif - /* Re-enable tag checking (TCO set on exception entry) */ -#ifdef CONFIG_ARM64_MTE -alternative_if ARM64_MTE - SET_PSTATE_TCO(0) -alternative_else_nop_endif -#endif - /* * Registers that may be useful after this macro is invoked: * |