[PATCH v4 05/18] KVM: arm64: selftests: Add support for cpu_relax

[Raghavendra Rao Ananta]

Implement the guest helper routine, cpu_relax(), to yield
the processor to other tasks.

The function was derived from
arch/arm64/include/asm/vdso/processor.h.

Signed-off-by: Raghavendra Rao Ananta <rananta at google.com>
Reviewed-by: Oliver Upton <oupton at google.com>
Reviewed-by: Andrew Jones <drjones at redhat.com>
---
 tools/testing/selftests/kvm/include/aarch64/processor.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tools/testing/selftests/kvm/include/aarch64/processor.h b/tools/testing/selftests/kvm/include/aarch64/processor.h
index ac8b63f8aab7..166d273ad715 100644
--- a/tools/testing/selftests/kvm/include/aarch64/processor.h
+++ b/tools/testing/selftests/kvm/include/aarch64/processor.h
@@ -134,6 +134,11 @@ void vm_install_exception_handler(struct kvm_vm *vm,
 void vm_install_sync_handler(struct kvm_vm *vm,
 		int vector, int ec, handler_fn handler);
 
+static inline void cpu_relax(void)
+{
+	asm volatile("yield" ::: "memory");
+}
+
 #define isb()		asm volatile("isb" : : : "memory")
 #define dsb(opt)	asm volatile("dsb " #opt : : : "memory")
 #define dmb(opt)	asm volatile("dmb " #opt : : : "memory")
-- 
2.33.0.153.gba50c8fa24-goog