Re: [PATCH v2] riscv: Add sysctl to control discard of vstate during syscall

From: Drew Fustini <fustini@kernel.org>
To: Vivian Wang <wangruikang@iscas.ac.cn>
Cc: "Darius Rad" <darius@bluespec.com>,
	"Paul Walmsley" <paul.walmsley@sifive.com>,
	"Palmer Dabbelt" <palmer@dabbelt.com>,
	"Alexandre Ghiti" <alex@ghiti.fr>,
	"Samuel Holland" <samuel.holland@sifive.com>,
	"Björn Töpel" <bjorn@rivosinc.com>,
	"Andy Chiu" <andybnac@gmail.com>,
	"Conor Dooley" <conor.dooley@microchip.com>,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
	"Drew Fustini" <dfustini@tenstorrent.com>
Subject: Re: [PATCH v2] riscv: Add sysctl to control discard of vstate during syscall
Date: Mon, 11 Aug 2025 22:46:05 -0700	[thread overview]
Message-ID: <aJrVHenvkMTRYcsS@x1> (raw)
In-Reply-To: <5a96d08e-0714-4925-a9c4-ea66549623d1@iscas.ac.cn>

On Sun, Aug 10, 2025 at 05:52:54PM +0800, Vivian Wang wrote:
> >   Discarding vector state on syscall entry can help identify userpace
> >   programs that are mistakenly relying on vector state being preserved
> >   across syscalls. This can be useful for debugging and test suites.
> >   However, this behavior can negatively impact performance on some
> >   RISC-V implementations.
> >
> >   Say Y here if you want mandatory clobbering of vector state before
> >   entering all syscalls. If you select N, then userspace can still
> >   eanble it via the abi.riscv_v_vstate_discard sysctl knob.
> 
> Typo: eanble -> enable
> 
> Also, I think it kinda makes the false impression that the sysctl knob
> is only available with this set to N? I think this should be structured
> to say something like this being the default value, and also say that
> userspace can override this behavior system-wide via the sysctl knob.

Thanks, that is a good point that I should clarify that the user can
still override via the sysctl knob regardless of whether choosing Y or N
for this Kconfig option.

-Drew

_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv