From: Xi Ruoyao <xry111@xry111.site>
To: Huacai Chen <chenhuacai@kernel.org>
Cc: WANG Xuerui <kernel@xen0n.name>,
Eric Biederman <ebiederm@xmission.com>,
Kees Cook <keescook@chromium.org>,
Tiezhu Yang <yangtiezhu@loongson.cn>,
Jinyang He <hejinyang@loongson.cn>,
Jiaxun Yang <jiaxun.yang@flygoat.com>,
loongarch@lists.linux.dev, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH] LoongArch: Fix and simplify fcsr initialization on execve
Date: Tue, 02 Jan 2024 16:09:00 +0800 [thread overview]
Message-ID: <22af410fe1f60e7fc04cafbe03cfc50b36b53ae3.camel@xry111.site> (raw)
In-Reply-To: <CAAhV-H6dJtc3ZpEBnJzKdh691KQck771KOR0Lj41VLZ-Rc1ZwQ@mail.gmail.com>
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. 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). And 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 hardware
> > 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.
>
>
--
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University
prev parent reply other threads:[~2024-01-02 8:09 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-01 17:21 Xi Ruoyao
2024-01-02 2:35 ` Huacai Chen
2024-01-02 8:09 ` Xi Ruoyao [this message]
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