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Tue, 2 Jan 2024 03:09:04 -0500 (EST) Message-ID: <22af410fe1f60e7fc04cafbe03cfc50b36b53ae3.camel@xry111.site> Subject: Re: [PATCH] LoongArch: Fix and simplify fcsr initialization on execve From: Xi Ruoyao To: Huacai Chen Cc: WANG Xuerui , Eric Biederman , Kees Cook , Tiezhu Yang , Jinyang He , Jiaxun Yang , loongarch@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Date: Tue, 02 Jan 2024 16:09:00 +0800 In-Reply-To: References: <20240101172143.14530-2-xry111@xry111.site> Autocrypt: addr=xry111@xry111.site; prefer-encrypt=mutual; keydata=mDMEYnkdPhYJKwYBBAHaRw8BAQdAsY+HvJs3EVKpwIu2gN89cQT/pnrbQtlvd6Yfq7egugi0HlhpIFJ1b3lhbyA8eHJ5MTExQHhyeTExMS5zaXRlPoiTBBMWCgA7FiEEkdD1djAfkk197dzorKrSDhnnEOMFAmJ5HT4CGwMFCwkIBwICIgIGFQoJCAsCBBYCAwECHgcCF4AACgkQrKrSDhnnEOPHFgD8D9vUToTd1MF5bng9uPJq5y3DfpcxDp+LD3joA3U2TmwA/jZtN9xLH7CGDHeClKZK/ZYELotWfJsqRcthOIGjsdAPuDgEYnkdPhIKKwYBBAGXVQEFAQEHQG+HnNiPZseiBkzYBHwq/nN638o0NPwgYwH70wlKMZhRAwEIB4h4BBgWCgAgFiEEkdD1djAfkk197dzorKrSDhnnEOMFAmJ5HT4CGwwACgkQrKrSDhnnEOPjXgD/euD64cxwqDIqckUaisT3VCst11RcnO5iRHm6meNIwj0BALLmWplyi7beKrOlqKfuZtCLbiAPywGfCNg8LOTt4iMD 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: 6395A100017 X-Rspam-User: X-Stat-Signature: 9jmjimq77kmhjphig5dewiisc7i8rww5 X-Rspamd-Server: rspam03 X-HE-Tag: 1704182957-620958 X-HE-Meta: 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 YM8nPJNg QPh7APz8EuHYHV20iSo38DRf2/8AyTmXhU9avw7WidRS7gAqoFQpL17GR52p0qFRNWw6AAQM3HeRZCaYfnxdsyMsvVX559TAaTTHNfsoT7WVrEpjbq8JiY2mdaY1zNOyC0Sz1j/BiQNolNMD6gyc4hccn8pWsgNQa7YrlBF+leMBRBmxqEPXoBgOVN9nX2SdMoykejt98KZTYnO/l0h9VKtwJw3bXDl/Fyij6lovT5I2SGeL4xKQVRje6/rUUYEZ5BiDFoTBdf3stj3F2c5nXAxwRx3uQiS8UvsMl X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, 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 10:35 +0800, Huacai Chen wrote: /* snip */ > > 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) as I don't have a running MIPS hardware > > now. > I think you can use QEMU. :) I'll investigate it later. > > So for LoongArch, just remove the current->thread.fpu.fcsr setting from > > SET_PERSONALITY2 and do it in start_thread, after lose_fpu(0).=C2=A0 An= d we > > just set it to 0, instead of boot_cpu_data.fpu_csr0 (because we should > > provide the userspace a consistent configuration, no matter how hardwar= e > > and firmware behave). > I still prefer to set fcsr to boot_cpu_data.fpu_csr0, because we will > add LoongArch32 later, not sure whether something will change. I just seen fpu_csr0 is initialized to FPU_CSR_RN which is just 0 for LA64, so my concern about firmware & hardware leaving non-zero FCSR is not valid. I'll send v2 to keep using boot_cpu_data.fpu_csr0 then. >=20 >=20 --=20 Xi Ruoyao School of Aerospace Science and Technology, Xidian University