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Tue, 2 Jan 2024 05:48:31 -0500 (EST) Message-ID: <7a6aa1bbdbbe2e63ae96ff163fab0349f58f1b9e.camel@xry111.site> Subject: MIPS: fcsr31 may be dirty after execve when kernel preempt is enabled (was: Re: [PATCH v2] LoongArch: Fix and simplify fcsr initialization on execve) From: Xi Ruoyao To: Huacai Chen , WANG Xuerui , Jiaxun Yang Cc: Eric Biederman , Kees Cook , Tiezhu Yang , Jinyang He , loongarch@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, linux-mips@vger.kernel.org Date: Tue, 02 Jan 2024 18:48:27 +0800 In-Reply-To: References: <20240102101711.10872-2-xry111@xry111.site> Autocrypt: addr=xry111@xry111.site; prefer-encrypt=mutual; keydata=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 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.2 MIME-Version: 1.0 X-Rspamd-Queue-Id: DF2D814001A X-Rspam-User: X-Stat-Signature: 3d7iebfosbeg4n6oqjj6imm1dccok13r X-Rspamd-Server: rspam01 X-HE-Tag: 1704192520-371492 X-HE-Meta: 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 V45PPjI9 4IQHLUabxG2yI1X949WkNqsLtGU3sjYELpWv2whN32hypKMSMFPk8M0JiJaaFYFqAE5OUk/UjapSM2s2jmPqXbAyatVrL28UgGT/DLygMpqvsqw4fse4zPcP4t4t2N0hopNB0/8W2HXIvnw8sV2XeonlNGabSxp51KZFkzmX4bAxehkV0tGhow3nAtTmXCgpIDiF5wOBMUjDDSXwrMUiYcBZiavGEu5UKueDzUgrb+TpQgdbIQue7gskWoXmGsD1AfkR5FYOlQcxLYaENv9ZHIuTgyrntyYU/hYRUixv9dJfoVyFw/wsLBW8ULZrCV7KFcwS8 X-Bogosity: Ham, tests=bogofilter, spamicity=0.003318, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 2024-01-02 at 18:25 +0800, Xi Ruoyao wrote: > On Tue, 2024-01-02 at 18:17 +0800, Xi Ruoyao wrote: > > The only other architecture setting FCSR in SET_PERSONALITY2 is MIPS. > > They do this for supporting different FP flavors (NaN encodings etc). > > which do not exist on LoongArch.=C2=A0 I'm not sure how MIPS evades the= issue > > (or maybe it's just buggy too) but I'll investigate it later. >=20 > Phew.=C2=A0 I just managed to recommission my 3A4000 and I can reproduce = the > issue as well with Linux 5.18.1 (the latest kernel release when I > decommissioned it) and CONFIG_PREEMPT=3Dy. >=20 > % cat measure.c > #include > int main() { return fetestexcept(FE_INEXACT); } >=20 > % echo $((1./3)) > 0.33333333333333331 >=20 > % while ./a.out; do ; done > (stopped in seconds) >=20 > I'm building the mainline kernel on the 3A4000 now, will see if the > issue still exists... Still happening with 6.7.0-rc8. I'm not sure how to fix it for MIPS.=20 Maybe lose_fpu in SET_PERSONALITY2? But to me doing so will be really nasty. Anyway I'll leave this for MIPS maintainers. --=20 Xi Ruoyao School of Aerospace Science and Technology, Xidian University