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Fri, 16 Oct 2026 14:45:01 -0700 (PDT) Date: Fri, 16 Oct 2026 16:45:00 -0500 From: Andy Chiu To: Radim =?iso-8859-1?Q?Krcm=E1r?= Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, Paul Walmsley , Palmer Dabbelt , Alexandre Ghiti , Samuel Holland , Andy Chiu , Guodong Xu , Zong Li , Charlie Jenkins Subject: Re: riscv: hwprobe: Report Supm only when available Message-ID: References: <20261006075303.205216-1-radim.krcmar@oss.qualcomm.com> <20261006075303.205216-5-radim.krcmar@oss.qualcomm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Fri, Oct 16, 2026 at 04:26:03PM -0500, Andy Chiu wrote: > On Tue, Oct 06, 2026 at 09:53:01AM +0200, Radim Krcmár wrote: > > The RISC-V ISA defines Supm as > > > > "An extension that indicates that there is pointer-masking support > > available in user mode, with some facility provided in the application > > execution environment to control pointer masking." > > > > Our facility always returns -EINVAL unless Supm support is configured, > > the pointer masking ISA extension is globally present, and the user-mode > > is running in 64-bit mode. > > > > Hiding Supm in compat tasks would add complexity that doesn't seem > > justified as 32-bit code has no reason to look at Supm anyway. > > Reporting based on the a global sysctl toggle isn't done. > > > > Do not report Supm when some harts lack the extension, because it's not > > available on any hart in that case. > > > > (Reporting Supm when only PMLEN=0 is supported isn't great, but doesn't > > violate the text of the extension and we ought to have Supm7 and Supm16 > > extensions if we care about precision.) > > > > Fixes: 3c2e0aff7b4f ("riscv: hwprobe: Export the Supm ISA extension") > > Signed-off-by: Radim Krcmár > > Reviewed-by: Andy Chiu > > > --- > > The compat hiding and global sysctl toggle better fit in Andy's series. > > > > Sorry, I am not aware of any ongoing series that does the compat hiding, > but I will keep an eye on it. Now I know the series you mentioned. That series was dropped because the mechanism was not in flavor of reviewers and we are going to deprecate the prctl[1]. But I can see there is still a need for understanding if an extension exists at runtime. We will take time to revisit that [1]: https://lore.kernel.org/all/20261007085126.222688-1-samuel.holland@sifive.com/ Thanks, Andy