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

[Yasumasa Suenaga]

On 2020/07/27 19:36, Baesken, Matthias wrote:
> Hi Yasumasa, I put your patch into our internal  nightly  build/test  queue .

Thanks!

>>    - Hyper-V is detected on Windows in spite of running on host OS
> 
> So it is in your case a host that  runs  Hyper-V guests.  And the host  reports too  "HyperV virtualization detected" .
> Do I get you  right ?

Yes, that's right!

> Maybe we should be more specific in this case (however I did not see much problem so far with the  current output ).
> 
>>    - Call CPUID with other than EAX = 40000000h (it is not described in the spec [1])
> 
> I think we had  some virtualizations that needed checking  CPUID with other than EAX = 40000000h  for detection,
>   But might be these were old or buggy versions , cannot find much details about it atm .

As David shows, virt-what checks CPUID with other than EAX = 40000000h, but at least, current supported hypervisor (VMware, Hyper-V, KVM, Xen) do not seem to need to do it.

>>    - Does not check CPUID hypervisor present bit [1]
> 
> Yes, this could/should indeed be added  ( we even did this in our internal JVM a while ago).
> 
>>    - Does not support x86 (32bit) platform
> 
> This is true , it was not added because   I think 32bit support has not much importance any more in current jdk .
> However in case the new version does  support 32bit too, it is for sure a good thing!

I found out "TODO support 32 bit" in current code, so I attempt to fix it :)


Thanks,

Yasumasa


> Best regards, Matthias
> 
> 
> 
> -----Original Message-----
> From: Yasumasa Suenaga <suenaga at oss.nttdata.com>
> Sent: Montag, 27. Juli 2020 06:25
> To: hotspot-runtime-dev at openjdk.java.net; Baesken, Matthias <matthias.baesken at sap.com>
> Cc: David Holmes <david.holmes at oracle.com>
> Subject: RFR: 8250598: Hyper-V is detected in spite of running on host OS
> 
> Hi all,
> 
> Please review this change:
> 
>     JBS: https://bugs.openjdk.java.net/browse/JDK-8250598
>     webrev: http://cr.openjdk.java.net/~ysuenaga/JDK-8250598/webrev.00/
> 
> When I got hs_err log on Windows, I saw "HyperV virtualization detected" in it in spite of running on host OS.
> 
> Hypervisor detector has been introduced in JDK-8219241, but it has some problems as below:
> 
>     - Hyper-V is detected on Windows in spite of running on host OS
>     - Call CPUID with other than EAX = 40000000h (it is not described in the spec [1])
>     - Does not check CPUID hypervisor present bit [1]
>     - Does not support x86 (32bit) platform
> 
> I've tested this change on submit repo, and have checked output from VM.info jcmd on following environment:
> 
>     - Windows x64 (host)
>     - Windows x64 (Hyper-V guest)
>     - Fedora32 x64 (Hyper-V guest)
>     - 32 bit JDK on Fedora32 x64 (Hyper-V guest)
> 
> 
> Thanks,
> 
> Yasumasa
> 
> 
> [1] https://kb.vmware.com/s/article/1009458
>