linux-kernel - Re: [PATCH v2 3/7] arm64: cpufeature: Fix the type of no FP/SIMD capability

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Message-ID: <20200110145055.GE8786@arrakis.emea.arm.com>
Date:   Fri, 10 Jan 2020 14:50:56 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     Suzuki K Poulose <suzuki.poulose@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        will@...nel.org, maz@...nel.org, mark.rutland@....com,
        dave.martin@....com, ard.biesheuvel@...aro.org,
        christoffer.dall@....com
Subject: Re: [PATCH v2 3/7] arm64: cpufeature: Fix the type of no FP/SIMD
 capability

On Tue, Dec 17, 2019 at 06:33:58PM +0000, Suzuki K Poulose wrote:
> The NO_FPSIMD capability is defined with scope SYSTEM, which implies
> that the "absence" of FP/SIMD on at least one CPU is detected only
> after all the SMP CPUs are brought up. However, we use the status
> of this capability for every context switch. So, let us change
> the scope to LOCAL_CPU to allow the detection of this capability
> as and when the first CPU without FP is brought up.
> 
> Also, the current type allows hotplugged CPU to be brought up without
> FP/SIMD when all the current CPUs have FP/SIMD and we have the userspace
> up. Fix both of these issues by changing the capability to
> BOOT_RESTRICTED_LOCAL_CPU_FEATURE.
> 
> Fixes: 82e0191a1aa11abf ("arm64: Support systems without FP/ASIMD")
> Cc: Will Deacon <will@...nel.org>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>

Reviewed-by: Catalin Marinas <catalin.marinas@....com>