From: Suzuki K Poulose <suzuki.poulose@arm.com>
To: James Morse <james.morse@arm.com>, linux-arm-kernel@lists.infradead.org
Cc: Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>
Subject: Re: [PATCH 1/3] arm64: cpufeature: Force HWCAP to be based on the sysreg visible to user-space
Date: Mon, 12 Sep 2022 16:20:56 +0100 [thread overview]
Message-ID: <f70bf438-4078-04d0-5782-dee33389205d@arm.com> (raw)
In-Reply-To: <20220909165938.3931307-2-james.morse@arm.com>
On 09/09/2022 17:59, James Morse wrote:
> arm64 advertises hardware features to user-space via HWCAPs, and by
> emulating access to the CPUs id registers. The cpufeature code has a
> sanitised system-wide view of an id register, and a sanitised user-space
> view of an id register, where some features use their 'safe' value
> instead of the hardware value.
>
> It is currently possible for a HWCAP to be advertised where the user-space
> view of the id register does not show the feature as supported.
> Erratum workaround need to remove both the HWCAP, and the feature from
> the user-space view of the id register. This involves duplicating the
> code, and spreading it over cpufeature.c and cpu_errata.c.
>
> Make the HWCAP code use the user-space view of id registers. This ensures
> the values never diverge, and allows erratum workaround to remove HWCAP
> by modifying the user-space view of the id register.
That sounds good to me.
>
> Signed-off-by: James Morse <james.morse@arm.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
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next prev parent reply other threads:[~2022-09-12 15:22 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-09 16:59 [PATCH 0/3] arm64: errata: remove BF16 HWCAP due to incorrect result on Cortex-A510 James Morse
2022-09-09 16:59 ` [PATCH 1/3] arm64: cpufeature: Force HWCAP to be based on the sysreg visible to user-space James Morse
2022-09-12 15:20 ` Suzuki K Poulose [this message]
2022-09-09 16:59 ` [PATCH 2/3] arm64: cpufeature: Expose get_arm64_ftr_reg() outside cpufeature.c James Morse
2022-09-12 15:22 ` Suzuki K Poulose
2022-09-09 16:59 ` [PATCH 3/3] arm64: errata: remove BF16 HWCAP due to incorrect result on Cortex-A510 James Morse
2022-09-12 15:30 ` Suzuki K Poulose
2022-09-15 13:39 ` James Morse
2022-09-09 18:29 ` [PATCH 0/3] " Robin Murphy
2022-09-15 13:39 ` James Morse
2022-09-15 14:21 ` Robin Murphy
2022-09-16 17:44 ` Catalin Marinas
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