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Message-ID: <f6e0b3a0e08a8100fa5dc9345af8582ff664321c.camel@xry111.site>
Subject: Re: [PATCH v2] LoongArch: Fix and simplify fcsr initialization on
 execve
From: Xi Ruoyao <xry111@xry111.site>
To: Huacai Chen <chenhuacai@kernel.org>, WANG Xuerui <kernel@xen0n.name>
Cc: Eric Biederman <ebiederm@xmission.com>, Kees Cook
 <keescook@chromium.org>,  Tiezhu Yang <yangtiezhu@loongson.cn>, Jinyang He
 <hejinyang@loongson.cn>, loongarch@lists.linux.dev,  linux-mm@kvack.org,
 linux-kernel@vger.kernel.org, stable@vger.kernel.org
Date: Tue, 02 Jan 2024 18:25:54 +0800
In-Reply-To: <20240102101711.10872-2-xry111@xry111.site>
References: <20240102101711.10872-2-xry111@xry111.site>
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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 i=
ssue
> (or maybe it's just buggy too) but I'll investigate it later.

Phew.  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.

% cat measure.c
#include <fenv.h>
int main() { return fetestexcept(FE_INEXACT); }

% echo $((1./3))
0.33333333333333331

% while ./a.out; do ; done
(stopped in seconds)

I'm building the mainline kernel on the 3A4000 now, will see if the
issue still exists...

--=20
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University