From: "Rémi Denis-Courmont" <remi@remlab.net>
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Subject: Re: [FFmpeg-devel] [PATCH] RISC-V:update ff_get_cpu_flags_riscv for RVV
Date: Fri, 21 Mar 2025 06:11:30 +0200
Message-ID: <82085B36-57F6-4554-A39A-43BAD09CD871@remlab.net> (raw)
In-Reply-To: <a7b912b6-14e1-437f-b7b1-df0530a2a9b9@iscas.ac.cn>
Hi,
Le 21 mars 2025 04:12:14 GMT+02:00, daichengrong <daichengrong@iscas.ac.cn> a écrit :
>
>在 2025/3/20 19:17:21, Rémi Denis-Courmont :
>> Hi,
>>
>> Le 20 mars 2025 11:27:39 GMT+02:00, daichengrong <daichengrong@iscas.ac.cn> a écrit :
>>>>> Availability of RVV and ZVBB should be determined with dl_hwcap.
>>>> No. That's completely superfluous since we already check for kernel support with hwprobe().
>>> No. If the operating system does not enable dl_hwcap support for rvv, an illegal instruction exception will be reported , even if the hardware and kernel support RVV.
>> And so what?
>
>When running tests/checkasm, if the operating system has RVV support disabled, the program reports illegal instructions and the test crashes.
No, it does not. We even test this multiple times a day in FATE.
>
>Linux localhost.localdomain 6.13.0 #1 SMP Tue Mar 4 09:23:35 CST 2025 riscv64 riscv64 riscv64 GNU/Linux
>
>[root@localhost checkasm]# echo 0 > /proc/sys/abi/riscv_v_default_allow
If you use that option, you are responsible for ensuring that libc will re-enable vectors using prctl() before running any programme or library with vector code. You just shot yourself in the foot.
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prev parent reply other threads:[~2025-03-21 4:11 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-03-14 10:32 daichengrong
2025-03-15 4:03 ` Rémi Denis-Courmont
2025-03-20 9:27 ` daichengrong
2025-03-20 11:17 ` Rémi Denis-Courmont
2025-03-21 2:12 ` daichengrong
2025-03-21 4:11 ` Rémi Denis-Courmont [this message]
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