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From: Catalin Marinas <catalin.marinas@arm.com>
To: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, will@kernel.org, maz@kernel.org,
	mark.rutland@arm.com, dave.martin@arm.com,
	ard.biesheuvel@linaro.org, christoffer.dall@arm.com,
	Will Deacon <will.deacon@arm.com>
Subject: Re: [PATCH v2 2/7] arm64: fpsimd: Make sure SVE setup is complete before SIMD is used
Date: Fri, 10 Jan 2020 11:51:32 +0000	[thread overview]
Message-ID: <20200110115132.GA8786@arrakis.emea.arm.com> (raw)
In-Reply-To: <20191217183402.2259904-3-suzuki.poulose@arm.com>

On Tue, Dec 17, 2019 at 06:33:57PM +0000, Suzuki K Poulose wrote:
> In-kernel users of NEON rely on may_use_simd() to check if the SIMD
> can be used. However, we must initialize the SVE before SIMD can
> be used. Add a sanity check to make sure that we have completed the
> SVE setup before anyone uses the SIMD.
> 
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> ---
> Discussion here : https://lkml.kernel.org/r/20191014145204.GS27757@arm.com

Re-reading this thread, I think the conclusion was more towards having a
WARN_ON in system_supports_fpsimd() (or may_use_simd()). We don't expect
code to start using neon before the SMP is initialised (other than
early_initcall(), the rest run after the secondary CPUs are brought up).

-- 
Catalin

WARNING: multiple messages have this Message-ID (diff)
From: Catalin Marinas <catalin.marinas@arm.com>
To: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: mark.rutland@arm.com, ard.biesheuvel@linaro.org, maz@kernel.org,
	Will Deacon <will.deacon@arm.com>,
	linux-kernel@vger.kernel.org, christoffer.dall@arm.com,
	will@kernel.org, dave.martin@arm.com,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 2/7] arm64: fpsimd: Make sure SVE setup is complete before SIMD is used
Date: Fri, 10 Jan 2020 11:51:32 +0000	[thread overview]
Message-ID: <20200110115132.GA8786@arrakis.emea.arm.com> (raw)
In-Reply-To: <20191217183402.2259904-3-suzuki.poulose@arm.com>

On Tue, Dec 17, 2019 at 06:33:57PM +0000, Suzuki K Poulose wrote:
> In-kernel users of NEON rely on may_use_simd() to check if the SIMD
> can be used. However, we must initialize the SVE before SIMD can
> be used. Add a sanity check to make sure that we have completed the
> SVE setup before anyone uses the SIMD.
> 
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> ---
> Discussion here : https://lkml.kernel.org/r/20191014145204.GS27757@arm.com

Re-reading this thread, I think the conclusion was more towards having a
WARN_ON in system_supports_fpsimd() (or may_use_simd()). We don't expect
code to start using neon before the SMP is initialised (other than
early_initcall(), the rest run after the secondary CPUs are brought up).

-- 
Catalin

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  reply	other threads:[~2020-01-10 11:51 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-17 18:33 [PATCH v2 0/7] arm64: Fix support for no FP/SIMD Suzuki K Poulose
2019-12-17 18:33 ` Suzuki K Poulose
2019-12-17 18:33 ` [PATCH v2 1/7] arm64: Introduce system_capabilities_finalized() marker Suzuki K Poulose
2019-12-17 18:33   ` Suzuki K Poulose
2020-01-10 14:50   ` Catalin Marinas
2020-01-10 14:50     ` Catalin Marinas
2019-12-17 18:33 ` [PATCH v2 2/7] arm64: fpsimd: Make sure SVE setup is complete before SIMD is used Suzuki K Poulose
2019-12-17 18:33   ` Suzuki K Poulose
2020-01-10 11:51   ` Catalin Marinas [this message]
2020-01-10 11:51     ` Catalin Marinas
2020-01-10 18:41     ` Suzuki Kuruppassery Poulose
2020-01-10 18:41       ` Suzuki Kuruppassery Poulose
2019-12-17 18:33 ` [PATCH v2 3/7] arm64: cpufeature: Fix the type of no FP/SIMD capability Suzuki K Poulose
2019-12-17 18:33   ` Suzuki K Poulose
2020-01-10 14:50   ` Catalin Marinas
2020-01-10 14:50     ` Catalin Marinas
2019-12-17 18:33 ` [PATCH v2 4/7] arm64: cpufeature: Set the FP/SIMD compat HWCAP bits properly Suzuki K Poulose
2019-12-17 18:33   ` Suzuki K Poulose
2020-01-10 14:51   ` Catalin Marinas
2020-01-10 14:51     ` Catalin Marinas
2019-12-17 18:34 ` [PATCH v2 5/7] arm64: ptrace: nofpsimd: Fail FP/SIMD regset operations Suzuki K Poulose
2019-12-17 18:34   ` Suzuki K Poulose
2020-01-10 15:12   ` Catalin Marinas
2020-01-10 15:12     ` Catalin Marinas
2020-01-10 18:42     ` Suzuki Kuruppassery Poulose
2020-01-10 18:42       ` Suzuki Kuruppassery Poulose
2019-12-17 18:34 ` [PATCH v2 6/7] arm64: signal: nofpsimd: Handle fp/simd context for signal frames Suzuki K Poulose
2019-12-17 18:34   ` Suzuki K Poulose
2020-01-10 12:34   ` Catalin Marinas
2020-01-10 12:34     ` Catalin Marinas
2019-12-17 18:34 ` [PATCH v2 7/7] arm64: nofpsmid: Handle TIF_FOREIGN_FPSTATE flag cleanly Suzuki K Poulose
2019-12-17 18:34   ` Suzuki K Poulose
2019-12-17 19:05   ` Marc Zyngier
2019-12-17 19:05     ` Marc Zyngier
2019-12-18 11:42     ` Suzuki Kuruppassery Poulose
2019-12-18 11:42       ` Suzuki Kuruppassery Poulose
2019-12-18 11:56       ` Marc Zyngier
2019-12-18 11:56         ` Marc Zyngier
2019-12-18 12:00         ` Suzuki Kuruppassery Poulose
2019-12-18 12:00           ` Suzuki Kuruppassery Poulose
2020-01-10 15:21           ` Marc Zyngier
2020-01-10 15:21             ` Marc Zyngier
2020-01-13 10:28             ` Suzuki Kuruppassery Poulose
2020-01-13 10:28               ` Suzuki Kuruppassery Poulose
2020-01-10 14:49   ` Catalin Marinas
2020-01-10 14:49     ` Catalin Marinas

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