PING: RFR: 8250598: Hyper-V is detected in spite of running on host OS

[Baesken, Matthias]

Hi Yasumasa ,  I'm more or less fine with the change .
But still not fully convinced  that removing  the iteration is a good thing .

http://cr.openjdk.java.net/~ysuenaga/JDK-8250598/webrev.01/src/hotspot/cpu/x86/vm_version_x86.cpp.frames.html

1827   for (base = 0x40000000; base < 0x40010000; base += 0x100) {
1828     check_virt_cpuid(base, registers);

I think just checking  "0x40000000" should work in most cases but if I remember correctly sometimes it was not enough .
See also  some references about Xen/KVM :

https://lists.linuxfoundation.org/pipermail/virtualization/2012-May/019974.html

"If compat mode for another h/v is enabled then those leaves will appear
at 0x40000000 and Xen's will be bumped up, so a fully Xen aware set of
drivers (or detection routine, etc) should check at 0x100 intervals
until 0x40010000 " 

and 

https://lore.kernel.org/patchwork/patch/394371/



And not so happy about the WMI  usage (called in early JVM startup) :

http://cr.openjdk.java.net/~ysuenaga/JDK-8250598/webrev.01/src/hotspot/os_cpu/windows_x86/vm_version_windows_x86.cpp.frames.html

bool VM_Version::is_in_VM() { ... }
 ...
}

 But if noone else complains about it, I guess it's okay .


Best regards, Matthias


>PING: Could you review this change?
>
>   JBS: https://bugs.openjdk.java.net/browse/JDK-8250598
>   webrev: http://cr.openjdk.java.net/~ysuenaga/JDK-8250598/webrev.01/
>
>Build change has been reviewed by Erik.
>