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References: <20210722175157.1367122-1-valentin.schneider@arm.com>
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From:   Ard Biesheuvel <ardb@kernel.org>
Date:   Fri, 23 Jul 2021 16:12:49 +0200
Message-ID: <CAMj1kXE8Yyn0orHe3DjFvCQ3k5mUKJF10BcJ3fJTessRoMShBA@mail.gmail.com>
Subject: Re: [PATCH 0/3] sched, x86, arm64: PREEMPT_RT, FPU and preemption
To:     Valentin Schneider <valentin.schneider@arm.com>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        linux-rt-users@vger.kernel.org, X86 ML <x86@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Steven Rostedt <rostedt@goodmis.org>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Ingo Molnar <mingo@kernel.org>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>, Mark Brown <broonie@kernel.org>,
        Dave Martin <Dave.Martin@arm.com>
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On Thu, 22 Jul 2021 at 19:53, Valentin Schneider
<valentin.schneider@arm.com> wrote:
>
> Hi folks,
>
> This stems from some more v5.13-rt1 breakage on arm64. This time per-CPU access
> safety isn't sufficient, we really need to keep preemption disabled.
>
> In a happy accident I stumbled on
>
>   cba08c5dc6dc ("x86/fpu: Make kernel FPU protection RT friendly")
>
> so I packaged what was done there into some common helpers and plastered them
> over the problematic areas.
>
> Cheers,
> Valentin
>
> Valentin Schneider (3):
>   sched/preempt: Introduce preempt_{enable, disable}_bh()
>   x86/fpu: Make FPU protection reuse common helper
>   arm64/fpsimd: Fix FPSIMD context handling vs PREEMPT_RT
>

Thanks for fixing this.

Reviewed-by: Ard Biesheuvel <ardb@kernel.org>


>  arch/arm64/kernel/fpsimd.c     |  6 ++++--
>  arch/x86/include/asm/fpu/api.h | 19 ++-----------------
>  include/linux/bottom_half.h    | 26 ++++++++++++++++++++++++++
>  3 files changed, 32 insertions(+), 19 deletions(-)
>
> --
> 2.25.1
>