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Fri, 13 Mar 2026 19:01:10 -0700 (PDT) Message-ID: <47e9a3e0-c056-41e8-a175-442a3ba7e355@sifive.com> Date: Fri, 13 Mar 2026 21:01:09 -0500 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 0/1] update riscv prctl for discovering V extension To: Yao Zihong , andybnac@gmail.com Cc: alex@ghiti.fr, eric.lin@sifive.com, greentime.hu@sifive.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, nick.hu@sifive.com, nylon.chen@sifive.com, paul.walmsley@sifive.com, pjw@kernel.org, vincent.chen@sifive.com, yongxuan.wang@sifive.com, zong.li@sifive.com References: <20260117233228.36088-1-andybnac@gmail.com> <20260313092012.64446-1-zihong.plct@isrc.iscas.ac.cn> Content-Language: en-US From: Samuel Holland In-Reply-To: <20260313092012.64446-1-zihong.plct@isrc.iscas.ac.cn> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi, On 2026-03-13 4:19 AM, Yao Zihong wrote: > It has been a while since the last activity on this thread, > so I would like to gently ping for comments. There was some off-list discussion about this around this time (anyone involved please correct me, it has been several weeks), and my understanding of the sentiment was that: 1) These sysctl and prctl() interfaces were introduced because adding vector state to the signal frame was technically an ABI break, due to increasing the minimum signal stack size. The prctl() provided an escape hatch for users to run existing software that used a smaller signal stack size. Notably, this existing software necessarily did not use RVV, because any C runtime that supported RVV would have enforced a larger minimum signal stack size. 2) Using these interfaces for another reason is unsupported, and anyone doing so gets to keep both pieces. Software that was aware of RVV at compile time is not expected to ever run with the sysctl/prctl() disabled at runtime. 3) Therefore, hwprobe() is sufficient for detecting the presence of the various vector extensions. The case where hwprobe() says RVV is available, but its usage traps, is considered a configuration error. Regards, Samuel