During testing of JDK-8218847 changes I found few failures. This is one of them.

With "-XX:+UnlockExperimentalVMOptions -XX:+EnableJVMCI -XX:-UseJVMCICompiler" flags
test/hotspot/jtreg/compiler/graalunit/DebugTest.java test failed with IllegalCallerException pointing to different modules:

org.graalvm.compiler.debug.test.TimerKeyTest started (4 of 5)
  test2: FAILED
test2(org.graalvm.compiler.debug.test.TimerKeyTest)
java.lang.ExceptionInInitializerError
at jdk.internal.vm.compiler@13-internal/org.graalvm.compiler.serviceprovider.GraalServices.getThreadAllocatedBytes(GraalServices.java:243)
at jdk.internal.vm.compiler@13-internal/org.graalvm.compiler.serviceprovider.GraalServices.getCurrentThreadAllocatedBytes(GraalServices.java:255)
at org.graalvm.compiler.debug.test.TimerKeyTest.assumeManagementLibraryIsLoadable(TimerKeyTest.java:59)
at org.graalvm.compiler.debug.test.TimerKeyTest.checkCapabilities(TimerKeyTest.java:51)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
...
Caused by: java.lang.IllegalCallerException: jdk.vm.ci.hotspot.aarch64 is not open to module jdk.internal.vm.compiler
at java.base/java.lang.Module.addOpens(Module.java:762)
at jdk.internal.vm.compiler@13-internal/org.graalvm.compiler.serviceprovider.GraalServices.openJVMCITo(GraalServices.java:125)
at jdk.internal.vm.compiler@13-internal/org.graalvm.compiler.serviceprovider.GraalServices$1$1.next(GraalServices.java:95)
at jdk.internal.vm.compiler@13-internal/org.graalvm.compiler.serviceprovider.GraalServices.loadSingle(GraalServices.java:147)
at jdk.internal.vm.compiler@13-internal/org.graalvm.compiler.serviceprovider.JMXService.<clinit>(JMXService.java:51)

or

Caused by: java.lang.IllegalCallerException: jdk.vm.ci.runtime is not open to module jdk.internal.vm.compiler
at java.base/java.lang.Module.addOpens(Module.java:762)
at jdk.internal.vm.compiler@13-internal/org.graalvm.compiler.serviceprovider.GraalServices.openJVMCITo(GraalServices.java:125)

or

Caused by: java.lang.IllegalCallerException: jdk.vm.ci.code is not open to module jdk.internal.vm.compiler
at java.base/java.lang.Module.addOpens(Module.java:762)
at jdk.internal.vm.compiler@13-internal/org.graalvm.compiler.serviceprovider.GraalServices.openJVMCITo(GraalServices.java:125)