linux-kernel - Re: [PATCH 04/10] arm64: mops: document boot requirements for MOPS

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Message-ID: <ZBSCObGmIXjyeMA6@arm.com>
Date:   Fri, 17 Mar 2023 15:07:37 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     Kristina Martsenko <kristina.martsenko@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        Oliver Upton <oliver.upton@...ux.dev>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Zenghui Yu <yuzenghui@...wei.com>,
        Mark Rutland <mark.rutland@....com>,
        Mark Brown <broonie@...nel.org>,
        Luis Machado <luis.machado@....com>,
        Vladimir Murzin <vladimir.murzin@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 04/10] arm64: mops: document boot requirements for MOPS

On Thu, Feb 16, 2023 at 04:00:06PM +0000, Kristina Martsenko wrote:
> +  For CPUs with Memory Copy and Memory Set instructions (FEAT_MOPS):
> +
> +  - If the kernel is entered at EL1 and EL2 is present:
> +
> +    - HCRX_EL2.MSCEn (bit 11) must be initialised to 0b1.
> +
> +    - HCRX_EL2.MCE2 (bit 10) must be initialised to 0b0.

Regarding MCE2, does EL1 actually care if EL2 wants to handle all the
memcpy/memset exceptions? There may even be a valid case to do this at
EL2 if you run a guest that uses these instructions but has no clue on
how to deal with the specific exception like WrongOption.

-- 
Catalin