RFR: 8352730: RISC-V: Disable tests in qemu-user [v3]

[Fei Yang]

On Mon, 31 Mar 2025 10:45:54 GMT, Robbin Ehn <rehn at openjdk.org> wrote:

>> Hi, for you to consider.
>> 
>> These tests constantly fails in qemu-user.
>> Either the require host to be same arch explicit or implicit (sysroot).
>> E.g. "ptrace(PTRACE_ATTACH, ..) failed for 405157: Function not implemented'" for SA tests.
>> 
>> From bug:
>>> qemu-user/rv64 sets uarch to "qemu" in /proc/cpuinfo (qemu-system do not do that).
>>> We add this uarch to CPU feature string.
>>> This means we can use jtreg 'require' with cpu string to filter out tests in qemu-user.
>> 
>> Relevant qemu code:
>> https://github.com/qemu/qemu/blob/170825d14d88a1ce7fae98d5a928480f2f329b22/linux-user/riscv/target_proc.h#L29
>> 
>> Relevant hotspot code:
>> https://github.com/openjdk/jdk/blob/fa0b18bfde38ee2ffbab33a9eaac547fe8aa3c7c/src/hotspot/os_cpu/linux_riscv/vm_version_linux_riscv.cpp#L250
>> 
>> Tested that the require only filters out tests in qemu+riscv64.
>> 
>> Thanks!
>> 
>> /Robbin
>
> Robbin Ehn has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains seven additional commits since the last revision:
> 
>  - Merge branch 'master' into qemu-user-issues
>  - Revert
>  - Merge branch 'master' into qemu-user-issues
>  - Merge branch 'master' into qemu-user-issues
>  - more
>  - more
>  - native or very long

> qemu-user, "uarch: qemu" in cpuinfo: `[0.084s][info ][os,cpu] CPU: total 28 (initial active 28) qemu rv64 rvi rvm rva rvf rvd rvc rvv zba zbb zbs zfh zfhmin zvbc zvfh zicond` Hence we know this is qemu-user (only qemu-user sets uarch to qemu on riscv).
> 
> `/proc/cpuinfo` do not contain uarch: [0.053s][info ][os,cpu] CPU: total 8 (initial active 8) rv64 rvi rvm rva rvf rvd rvc zba zbb zbs zfh zfhmin zvfh zicond We have no clue if this is emulated or on real hardware, tests will be executed.
> 
> Tests are only excluded if we know it's qemu-user.


> qemu-user, "uarch: qemu" in cpuinfo: `[0.084s][info ][os,cpu] CPU: total 28 (initial active 28) qemu rv64 rvi rvm rva rvf rvd rvc rvv zba zbb zbs zfh zfhmin zvbc zvfh zicond` Hence we know this is qemu-user (only qemu-user sets uarch to qemu on riscv).
> 
> `/proc/cpuinfo` do not contain uarch: [0.053s][info ][os,cpu] CPU: total 8 (initial active 8) rv64 rvi rvm rva rvf rvd rvc zba zbb zbs zfh zfhmin zvfh zicond We have no clue if this is emulated or on real hardware, tests will be executed.
> 
> Tests are only excluded if we know it's qemu-user.

Sorry for not being clear enough. Yes, that's how it works with qemu-user for riscv.
Just wondering if it makes sense to extend this to other CPU platforms. There are two cases.
- Case 1: The tests are excluded as expected if we parses "qemu" in cpuinfo with qemu-user for another CPU, which is simiar with qemu-user for riscv. But I am not sure if there is one for now.
- Case 2: The tests are NOT excluded as there's no "qemu" in cpuinfo with qemu-user for another CPU. Then we still got test failures as before. But we are not causing any more regressions. I may consider that as a qemu-user issue for this CPU. And it could be fixed on the qemu-user side if it really helps people.

Maybe I am demanding too much about qemu-user. What do you think?

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PR Comment: https://git.openjdk.org/jdk/pull/24229#issuecomment-2791376594