linux-kernel - Re: [RFC PATCH] arm64/fpsimd: Don't disable softirq when touching FPSIMD/SVE state

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Message-ID: <20190213165227.7ekekkxazhbaqxoe@linutronix.de>
Date:   Wed, 13 Feb 2019 17:52:27 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:     Dave Martin <Dave.Martin@....com>,
        Julien Grall <julien.grall@....com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-rt-users@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH] arm64/fpsimd: Don't disable softirq when touching
 FPSIMD/SVE state

On 2019-02-13 16:40:00 [+0100], Ard Biesheuvel wrote:
> > > This is equal what x86 is currently doing. The naming is slightly
> > > different, there is irq_fpu_usable().
> >
> > Yes, I think it's basically the same idea.
> >
> > It's been evolving a bit on both sides, but is quite similar now.
> >
> 
> may_use_simd() only exists because we have a generic crypto SIMD
> helper, and so we needed something arch agnostic to wrap around
> irq_fpu_usable()

My question was more if this is helpful and we want to keep or if
it would be better to remove it and always disable BH as part of SIMD
operations.

Sebastian