linux-kernel - Re: [PATCH V2] LoongArch: Ensure FP/SIMD registers in the core dump file is up to date

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Message-ID: <CAAhV-H532djpsYDPGZxG9g8eiaq2UMGYX_+ADb4kaPpQmgTXYg@mail.gmail.com>
Date:   Sat, 26 Aug 2023 23:47:24 +0800
From:   Huacai Chen <chenhuacai@...nel.org>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Huacai Chen <chenhuacai@...ngson.cn>, loongarch@...ts.linux.dev,
        Xuefeng Li <lixuefeng@...ngson.cn>,
        Guo Ren <guoren@...nel.org>, Xuerui Wang <kernel@...0n.name>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        linux-kernel@...r.kernel.org, loongson-kernel@...ts.loongnix.cn,
        stable@...r.kernel.org
Subject: Re: [PATCH V2] LoongArch: Ensure FP/SIMD registers in the core dump
 file is up to date

On Sat, Aug 26, 2023 at 11:43 PM Greg KH <gregkh@...uxfoundation.org> wrote:
>
> On Sat, Aug 26, 2023 at 11:35:31PM +0800, Huacai Chen wrote:
> > On Sat, Aug 26, 2023 at 11:22 PM Greg KH <gregkh@...uxfoundation.org> wrote:
> > >
> > > On Sat, Aug 26, 2023 at 10:23:41PM +0800, Huacai Chen wrote:
> > > > This is a port of commit 379eb01c21795edb4c ("riscv: Ensure the value
> > > > of FP registers in the core dump file is up to date").
> > > >
> > > > The values of FP/SIMD registers in the core dump file come from the
> > > > thread.fpu. However, kernel saves the FP/SIMD registers only before
> > > > scheduling out the process. If no process switch happens during the
> > > > exception handling, kernel will not have a chance to save the latest
> > > > values of FP/SIMD registers. So it may cause their values in the core
> > > > dump file incorrect. To solve this problem, force fpr_get()/simd_get()
> > > > to save the FP/SIMD registers into the thread.fpu if the target task
> > > > equals the current task.
> > > >
> > > > Cc: stable@...r.kernel.org
> > > > Signed-off-by: Huacai Chen <chenhuacai@...ngson.cn>
> > > > ---
> > > > V2: Rename get_fpu_regs() to save_fpu_regs().
> > >
> > > What stable tree(s) is this for?
> > For 5.19+, but before 6.4 we should remove the call site in simd_get()
> > because that function doesn't exist.
>
> But this commit is already in the following released kernels:
>         5.10.62 5.13.14 5.14
Do you means commit 379eb01c21795edb4c ("riscv: Ensure the value of FP
registers in the core dump file is up to date")? That is a reference
commit, not a Fixes tag. This patch is for LoongArch and LoongArch
only exists after 5.19.

> so how can it be backported?
>
> totally confused,
>
> greg k-h