Memory Corruption in JDK-21 on x86_64 with AVX-512

[Vladimir Kozlov]

Hi,

After discussion we decided to postpone fix to 21.0.2.
There is no much time left before 21.0.1 is released and we still don't 
have regression test and did not review or fully tested the fix.

But because of severity of the issue and to be safe we decided to set 
UseAVX == 2 by default even on AVX512 CPUs in 21.0.1. And add release 
note about this. It is temporary solution until next update release 
21.0.2. We did similar thing (disabled avx512 instructions) in JDK 9.

I am also thinking about setting UseSVE to `false` by default on Aarch64 
with SVE since it could be affected too. We don't have such machine so I 
can't verify the fix.

Meanwhile I will work on test and fix for JDK 22. And I hope Xiaohong 
will help, when he is back from break, with SVE testing.

Regards,
Vladimir K

On 9/27/23 11:32 AM, Vladimir Kozlov wrote:
> https://bugs.openjdk.org/browse/JDK-8317121
> 
> On 9/27/23 11:19 AM, Vladimir Kozlov wrote:
>> Officially jdk21.0.1 is closed for fixes but we are discussing this 
>> issue now.
>>
>> I verified the suggested by Xiaohong fix:
>> retrun nullptr in StoreVectorNode::Ideal() and LoadVectorNode::Ideal().
>>
>> I will file a bug and follow the process.
>>
>> Regards,
>> Vladimir K
>>
>> On 9/27/23 9:54 AM, Viswanathan, Sandhya wrote:
>>> Copying Tobias.
>>>
>>>  From what I see JDK21 update schedule has a mid-October release plan 
>>> (https://wiki.openjdk.org/display/JDKUpdates/JDK+21u).
>>>
>>> Tobias, do you know the code freeze date for that. Hopefully, we 
>>> still have a couple of days left.
>>>
>>> At the minimum we should revert to return nullptr in both 
>>> LoadVectorMaskedNode::Ideal and StoreVectorMaskedNode::Ideal as a 
>>> workaround.
>>>
>>> Best Regards,
>>> Sandhya
>>>
>>> -----Original Message-----
>>> From: hotspot-compiler-dev <hotspot-compiler-dev-retn at openjdk.org> On 
>>> Behalf Of Carter Kozak
>>> Sent: Wednesday, September 27, 2023 7:26 AM
>>> To: Xiaohong Gong <Xiaohong.Gong at arm.com>; 
>>> hotspot-compiler-dev at openjdk.org
>>> Subject: Re: Memory Corruption in JDK-21 on x86_64 with AVX-512
>>>
>>> Thank you for such a quick diagnosis, I really appreciate it!
>>>
>>> While I don't have a good sense of the mapping between bug severity 
>>> and backport/release criteria, I suspect this issue may be a strong 
>>> candidate for an out-of-band jdk-21 release. I'm certainly biased 
>>> because I had invalid bytes silently persisted, and defer to folks 
>>> closer to the process.
>>>
>>> Best,
>>> Carter Kozak
>>>
>>> On Wed, Sep 27, 2023, at 02:57, Xiaohong Gong wrote:
>>>> Hi Carter,
>>>> Thanks for reporting this issue!
>>>> It seems the issue is caused by the calling of the super class’s 
>>>> “Ideal()” method in “LoadVectorMaskedNode::Ideal()” (code is: 
>>>> 8286941: Add mask IR for partial vector operations for ARM SVE by 
>>>> XiaohongGong · Pull Request #9037 · openjdk/jdk (github.com) 
>>>> <https://github.com/openjdk/jdk/pull/9037/files#diff-692826251cae892bc4737919579c6afbd317551cd507f99c7bd29d585c1282e2R1028>).
>>>> Some optimization applied on “LoadNode” is not suitable for 
>>>> “LoadVectorMaskedNode” now. Reverting it back to “return nullptr” 
>>>> can make your benchmark pass.
>>>> I will look at this issue and try to fix it next. Thanks!