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: Thu, 20 Mar 2025 13:17:21 +0200
Message-ID: <3736ED65-BD16-406B-996E-8C0E77668C8C@remlab.net> (raw)
In-Reply-To: <266f9b7f-5065-44ba-8037-5c44e197b85e@iscas.ac.cn>
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?
>> And we can't check for Zb* and Zv* with hwcap anyhow.
>>
>>> As those extensions rely on vector registers, kernel vector support
>>> is required to save the state of context switching.
>> No. Kernel context switching is already ascertained.
>No. The kernel will not save and restore vector registers if the program does not use vector instructions.
That optimisation is a kernel implementation detail that is completely irrelevant to the subject matter.
I still completely fail to see any justification for this patch.
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next prev parent reply other threads:[~2025-03-20 11:17 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 [this message]
2025-03-21 2:12 ` daichengrong
2025-03-21 4:11 ` Rémi Denis-Courmont
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