Check for KVM_CAP_USER_MEMORY

Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>

kvm.c

@@ -1,6 +1,7 @@
 #include "kvm/cpu.h"
 
 #include <linux/kvm.h>
+#include <stdbool.h>
 #include <stdlib.h>
 #include <fcntl.h>
 
@@ -9,6 +10,17 @@ struct kvm {
 	int			vmfd;
 };
 
+static inline bool kvm__supports_extension(struct kvm *self, unsigned int extension)
+{
+	int ret;
+
+	ret = ioctl(self->fd, KVM_CHECK_EXTENSION, extension);
+	if (ret < 0)
+		return false;
+
+	return ret;
+}
+
 static void die(const char *s)
 {
 	perror(s);
@@ -44,6 +56,9 @@ int main(int argc, char *argv[])
 	if (kvm.vmfd < 0)
 		die("open");
 
+	if (!kvm__supports_extension(&kvm, KVM_CAP_USER_MEMORY))
+		die("KVM_CAP_USER_MEMORY");
+
 	cpu = cpu__new();
 
 	cpu__reset(cpu);