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| author | Will Deacon <will@kernel.org> | 2020-06-30 14:02:22 +0100 |
|---|---|---|
| committer | Will Deacon <will@kernel.org> | 2020-11-09 21:49:34 +0000 |
| commit | 364a5a8ae8dc2dd457e2fefb4da3f3fd2c0ba8b1 (patch) | |
| tree | 4f905f7e5ebe04d52da859df00aa816827bc1558 /arch/arm64/Kconfig | |
| parent | 7cda23da52ad793a578d290e7fcc9cdc1698bba8 (diff) | |
| download | lwn-364a5a8ae8dc2dd457e2fefb4da3f3fd2c0ba8b1.tar.gz lwn-364a5a8ae8dc2dd457e2fefb4da3f3fd2c0ba8b1.zip | |
arm64: cpufeatures: Add capability for LDAPR instruction
Armv8.3 introduced the LDAPR instruction, which provides weaker memory
ordering semantics than LDARi (RCpc vs RCsc). Generally, we provide an
RCsc implementation when implementing the Linux memory model, but LDAPR
can be used as a useful alternative to dependency ordering, particularly
when the compiler is capable of breaking the dependencies.
Since LDAPR is not available on all CPUs, add a cpufeature to detect it at
runtime and allow the instruction to be used with alternative code
patching.
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
Diffstat (limited to 'arch/arm64/Kconfig')
| -rw-r--r-- | arch/arm64/Kconfig | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 1515f6f153a0..0f8b2e35ba99 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -1388,6 +1388,9 @@ config ARM64_PAN The feature is detected at runtime, and will remain as a 'nop' instruction if the cpu does not implement the feature. +config AS_HAS_LDAPR + def_bool $(as-instr,.arch_extension rcpc) + config ARM64_LSE_ATOMICS bool default ARM64_USE_LSE_ATOMICS |