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From: Catalin Marinas <catalin.marinas@arm.com>
To: Julien Grall <julien.grall@arm.com>
Cc: ard.biesheuvel@linaro.org, marc.zyngier@arm.com,
	Dave.Martin@arm.com, will.deacon@arm.com,
	linux-kernel@vger.kernel.org, kvmarm@lists.cs.columbia.edu,
Subject: Re: [PATCH v5 3/3] arm64/fpsimd: Don't disable softirq when touching FPSIMD/SVE state
Date: Mon, 3 Jun 2019 17:25:34 +0100
Message-ID: <20190603162534.GF63283@arrakis.emea.arm.com> (raw)
In-Reply-To: <20190521172139.21277-4-julien.grall@arm.com>

On Tue, May 21, 2019 at 06:21:39PM +0100, Julien Grall wrote:
> Since a softirq is supposed to check may_use_simd() anyway before
> attempting to use FPSIMD/SVE, there is limited reason to keep softirq
> disabled when touching the FPSIMD/SVE context. Instead, we can simply
> disable preemption and mark the FPSIMD/SVE context as in use by setting
> CPU's fpsimd_context_busy flag.
> +static void get_cpu_fpsimd_context(void)
> +{
> +	preempt_disable();
> +	__get_cpu_fpsimd_context();
> +}

Is there anything that prevents a softirq being invoked between
preempt_disable() and __get_cpu_fpsimd_context()?

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Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-21 17:21 [PATCH v5 0/3] " Julien Grall
2019-05-21 17:21 ` [PATCH v5 1/3] arm64/fpsimd: Remove the prototype for sve_flush_cpu_state() Julien Grall
2019-05-21 17:21 ` [PATCH v5 2/3] arch/arm64: fpsimd: Introduce fpsimd_save_and_flush_cpu_state() and use it Julien Grall
2019-06-04 11:12   ` Catalin Marinas
2019-06-04 11:52     ` Marc Zyngier
2019-05-21 17:21 ` [PATCH v5 3/3] arm64/fpsimd: Don't disable softirq when touching FPSIMD/SVE state Julien Grall
2019-06-03 16:25   ` Catalin Marinas [this message]
2019-06-03 21:21     ` Catalin Marinas
2019-06-04 10:35       ` Julien Grall

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