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

[Yasumasa Suenaga]

Hi David, Matthias, Martin,

I uploaded new webrev. Could you review again?

   http://cr.openjdk.java.net/~ysuenaga/JDK-8250598/webrev.02/

It generates runtime stub for hypervisor detection, and it can distinguish between Hyper-V host (root partition) and guest. And also it works on 32bit platforms.

I measured startup performance (java --version) with Measure-Command on PowerShell, this change is faster than current implementation.

TotalMilliseconds : 57.8196
TotalMilliseconds : 66.8379
TotalMilliseconds : 64.7693
TotalMilliseconds : 55.6546
TotalMilliseconds : 63.848
average : 61.78588

This change has passed tests on submit repo (mach5-one-ysuenaga-JDK-8250598-20200814-0119-13424118), and also it works fine on following environments:

   - Hyper-V host (Windows 10 x64)
   - Hyper-V guest (Windows 10 x64)
   - Hyper-V guest (Linux x64)
   - Hyper-V guest (32bit JDK on Linux x64)


Thanks,

Yasumasa


On 2020/08/13 20:39, David Holmes wrote:
> On 13/08/2020 5:39 pm, Yasumasa Suenaga wrote:
>> Hi Matthias, David,
>>
>> On 2020/08/13 15:52, Baesken, Matthias wrote:
>>>
>>>>
>>>> Should we make the change to determine just before it is needed (e.g. VM.info or hs_err log) at first?
>>>> It is out of scope of this change, so I want to work as another issue if it is needed.
>>>>
>>>
>>> Hi ,
>>> I think we better do not call into WMI , when  writing an hs_err file   .
>>
>> I found out from Hypervisor Top Level Functional Specification [1] section 2.4.8.
>> That says CPUID leaf 0x40000007 is available to the root partition only.
>>
>> I changed VM_Version::is_in_VM() as below, and it works fine.
>> (I use __cpuid intrinsic in here because this code would be compiled by cl.exe only.)
>>
>> ```
>> #include <intrin.h>
>>
>> #define EAX 0
>> #define EBX 1
>> #define ECX 2
>> #define EDX 3
>>
>> bool VM_Version::is_in_VM() {
>>    int regs[4];
>>    __cpuid(regs, 0x40000007);
>>
>>    // CPUID leaf 0x40000007 is available to the root partition only.
>>    return (regs[EAX] == 0x0) && (regs[EBX] == 0x0) && (regs[ECX] == 0x0) && (regs[EDX] == 0x0);
>> }
>> ```
>>
>> Also startup performance is better than WMI call.
>>
>> TotalMilliseconds : 66.7863
>> TotalMilliseconds : 56.8123
>> TotalMilliseconds : 57.0015
>> TotalMilliseconds : 62.4755
>> TotalMilliseconds : 67.7632
>> average : 62.16776
>>
>> If you are ok this change, I will update webrev, and will send review request.
>> (new webrev will include both loop for CPUID leaf and renaming is_in_VM)
> 
> If it works and addresses the startup hit then I'm fine with it - but still can't actually review the code.
> 
> Thanks,
> David
> 
>>
>> Thanks,
>>
>> Yasumasa
>>
>>
>> [1] https://github.com/MicrosoftDocs/Virtualization-Documentation/raw/master/tlfs/Hypervisor%20Top%20Level%20Functional%20Specification%20v6.0b.pdf
>>
>>
>>> Best regards, Matthias
>>>
>>>
>>>
>>> -----Original Message-----
>>> From: Yasumasa Suenaga <suenaga at oss.nttdata.com>
>>> Sent: Donnerstag, 13. August 2020 06:15
>>> To: David Holmes <david.holmes at oracle.com>; Baesken, Matthias <matthias.baesken at sap.com>; hotspot-runtime-dev at openjdk.java.net; build-dev at openjdk.java.net
>>> Cc: Doerr, Martin <martin.doerr at sap.com>
>>> Subject: Re: PING: RFR: 8250598: Hyper-V is detected in spite of running on host OS
>>>
>>> On 2020/08/13 11:54, David Holmes wrote:
>>>> On 13/08/2020 11:12 am, Yasumasa Suenaga wrote:
>>>>> Hi Matthias, David,
>>>>>
>>>>> I measured startup benchmarks with `Measure-Command {.\jdk\build\windows-x86_64-server-release\images\jdk\bin\java.exe --version}` on PowerShell.
>>>>>
>>>>> * PC: Ryzen 3 3300X, 16GB memory
>>>>> * OS: Windows 10 x64 (May 2020 Update)
>>>>> * Java: jdk/jdk revision 60537
>>>>>       (Compiled by VS 2019 (16.7.0))
>>>>>
>>>>> * without patch
>>>>> TotalMilliseconds : 70.2124
>>>>> TotalMilliseconds : 64.4465
>>>>> TotalMilliseconds : 59.0854
>>>>> TotalMilliseconds : 68.0255
>>>>> TotalMilliseconds : 72.6467
>>>>> average : 66.8833
>>>>>
>>>>> * with webrev.01
>>>>> TotalMilliseconds : 81.7185
>>>>> TotalMilliseconds : 68.539
>>>>> TotalMilliseconds : 85.7226
>>>>> TotalMilliseconds : 72.6584
>>>>> TotalMilliseconds : 75.6091
>>>>> average : 76.84952
>>>>>
>>>>> Overhead of WMI seems to be +10ms in this case.
>>>>
>>>> Which is nearly 15%! Sorry but I just know Claes will be very unhappy if this were to go in as-is.
>>>
>>> Should we make the change to determine just before it is needed (e.g. VM.info or hs_err log) at first?
>>> It is out of scope of this change, so I want to work as another issue if it is needed.
>>>
>>>
>>> Yasumasa
>>>
>>>
>>>> David
>>>> -----
>>>>
>>>>>
>>>>> Yasumasa
>>>>>
>>>>>
>>>>> On 2020/08/13 0:05, Baesken, Matthias wrote:
>>>>>>> I understand that if the process runs on Xen on other hypervisor (e.g. KVM), information for Xen would be set between 0x40000100 and 0x40010000.
>>>>>>> Ok, I will not remove the loop in new webrev, and will add comment about it.
>>>>>>
>>>>>> Hi Yasumasa  , thanks !
>>>>>>
>>>>>> Regarding the WMI overhead , if you could  get some more info on this it would be better to judge if it is perfectly okay or concerning .
>>>>>>
>>>>>> (I remember that I looked into it a couple of years ago , but decided not to use it in early VM startup ;  but have to confess this was just based on a "gut feeling",
>>>>>>    No micro benchmarks  )
>>>>>>
>>>>>> Best regards, Matthias
>>>>>>
>>>>>>