cpu: Check the KVM API version with a static_assert instead of macros.

Change-Id: Id8d52e25c4582ad802ee59facad5a1c31c2aa216
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/45743
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/cpu/kvm/vm.cc

@@ -53,11 +53,14 @@
 #include "params/KvmVM.hh"
 #include "sim/system.hh"
 
-#define EXPECTED_KVM_API_VERSION 12
+namespace
+{
 
-#if EXPECTED_KVM_API_VERSION != KVM_API_VERSION
-#error Unsupported KVM version
-#endif
+constexpr int ExpectedKvmApiVersion = 12;
+static_assert(KVM_API_VERSION == ExpectedKvmApiVersion,
+        "Unsupported KVM version");
+
+} // anonymous namespace
 
 Kvm *Kvm::instance = NULL;
 
@@ -75,7 +78,7 @@ Kvm::Kvm()
         fatal("KVM: Failed to open /dev/kvm\n");
 
     apiVersion = ioctl(KVM_GET_API_VERSION);
-    if (apiVersion != EXPECTED_KVM_API_VERSION)
+    if (apiVersion != ExpectedKvmApiVersion)
         fatal("KVM: Incompatible API version\n");
 
     vcpuMMapSize = ioctl(KVM_GET_VCPU_MMAP_SIZE);