KVM: selftests: Define cpu_relax() helpers for s390 and x86

Add cpu_relax() for s390 and x86 for use in arch-agnostic tests.  arm64
already defines its own version.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220226001546.360188-28-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/tools/testing/selftests/kvm/include/s390x/processor.h b/tools/testing/selftests/kvm/include/s390x/processor.h
index e0e96a5..255c9b9 100644 (file)
--- a/tools/testing/selftests/kvm/include/s390x/processor.h
+++ b/tools/testing/selftests/kvm/include/s390x/processor.h
@@ -5,6 +5,8 @@
 #ifndef SELFTEST_KVM_PROCESSOR_H
 #define SELFTEST_KVM_PROCESSOR_H
 
+#include <linux/compiler.h>
+
 /* Bits in the region/segment table entry */
 #define REGION_ENTRY_ORIGIN    ~0xfffUL /* region/segment table origin    */
 #define REGION_ENTRY_PROTECT   0x200    /* region protection bit          */
@@ -19,4 +21,10 @@
 #define PAGE_PROTECT   0x200           /* HW read-only bit  */
 #define PAGE_NOEXEC    0x100           /* HW no-execute bit */
 
+/* Is there a portable way to do this? */
+static inline void cpu_relax(void)
+{
+       barrier();
+}
+
 #endif

diff --git a/tools/testing/selftests/kvm/include/x86_64/processor.h b/tools/testing/selftests/kvm/include/x86_64/processor.h
index 8a470da..37db341 100644 (file)
--- a/tools/testing/selftests/kvm/include/x86_64/processor.h
+++ b/tools/testing/selftests/kvm/include/x86_64/processor.h
@@ -363,6 +363,11 @@ static inline unsigned long get_xmm(int n)
        return 0;
 }
 
+static inline void cpu_relax(void)
+{
+       asm volatile("rep; nop" ::: "memory");
+}
+
 bool is_intel_cpu(void);
 bool is_amd_cpu(void);