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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 1/7] arm64: Introduce system_capabilities_finalized() marker
Date: Fri, 10 Jan 2020 14:50:19 +0000	[thread overview]
Message-ID: <20200110145019.GD8786@arrakis.emea.arm.com> (raw)
In-Reply-To: <20191217183402.2259904-2-suzuki.poulose@arm.com>

On Tue, Dec 17, 2019 at 06:33:56PM +0000, Suzuki K Poulose wrote:
> We finalize the system wide capabilities after the SMP CPUs
> are booted by the kernel. This is used as a marker for deciding
> various checks in the kernel. e.g, sanity check the hotplugged
> CPUs for missing mandatory features.
> 
> However there is no explicit helper available for this in the
> kernel. There is sys_caps_initialised, which is not exposed.
> The other closest one we have is the jump_label arm64_const_caps_ready
> which denotes that the capabilities are set and the capability checks
> could use the individual jump_labels for fast path. This is
> performed before setting the ELF Hwcaps, which must be checked
> against the new CPUs. We also perform some of the other initialization
> e.g, SVE setup, which is important for the use of FP/SIMD
> where SVE is supported. Normally userspace doesn't get to run
> before we finish this. However the in-kernel users may
> potentially start using the neon mode. So, we need to
> reject uses of neon mode before we are set. Instead of defining
> a new marker for the completion of SVE setup, we could simply
> reuse the arm64_const_caps_ready and enable it once we have
> finished all the setup. Also we could expose this to the
> various users as "system_capabilities_finalized()" to make
> it more meaningful than "const_caps_ready".
> 
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>

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

  reply	other threads:[~2020-01-10 14:50 UTC|newest]

Thread overview: 24+ 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 ` [PATCH v2 1/7] arm64: Introduce system_capabilities_finalized() marker Suzuki K Poulose
2020-01-10 14:50   ` Catalin Marinas [this message]
2019-12-17 18:33 ` [PATCH v2 2/7] arm64: fpsimd: Make sure SVE setup is complete before SIMD is used Suzuki K Poulose
2020-01-10 11:51   ` Catalin Marinas
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
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
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
2020-01-10 15:12   ` Catalin Marinas
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
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 19:05   ` Marc Zyngier
2019-12-18 11:42     ` Suzuki Kuruppassery Poulose
2019-12-18 11:56       ` Marc Zyngier
2019-12-18 12:00         ` Suzuki Kuruppassery Poulose
2020-01-10 15:21           ` Marc Zyngier
2020-01-13 10:28             ` Suzuki Kuruppassery Poulose
2020-01-10 14:49   ` Catalin Marinas
2020-03-27 13:04 [PATCH v2 1/7] arm64: Introduce system_capabilities_finalized() marker Billie Teall

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