arm64: Implement cpu_relax as yield

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ARM64 has the yield nop hint which has the intended semantics of
cpu_relax. Implement.

The immediate application is ARM CPU emulators. An emulator can take
advantage of the yield hint to de-prioritise an emulated CPU in favor
of other emulation tasks. QEMU A64 SMP emulation has yield awareness,
and sees a significant boot time performance increase with this change.

Signed-off-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

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Peter Crosthwaite 2015-03-02 19:19:14 +00:00 • committed by Will Deacon

parent 06e5801b8c

commit 1baa82f480

1 changed files with 5 additions and 1 deletions

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arch/arm64/include/asm/processor.h

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