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Date:   Tue, 22 Feb 2022 12:53:46 +0000
From:   Catalin Marinas <catalin.marinas@arm.com>
To:     Mark Brown <broonie@kernel.org>
Cc:     Will Deacon <will@kernel.org>, Marc Zyngier <maz@kernel.org>,
        Shuah Khan <skhan@linuxfoundation.org>,
        Shuah Khan <shuah@kernel.org>,
        Alan Hayward <alan.hayward@arm.com>,
        Luis Machado <luis.machado@arm.com>,
        Salil Akerkar <Salil.Akerkar@arm.com>,
        Basant Kumar Dwivedi <Basant.KumarDwivedi@arm.com>,
        Szabolcs Nagy <szabolcs.nagy@arm.com>,
        James Morse <james.morse@arm.com>,
        Alexandru Elisei <alexandru.elisei@arm.com>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        linux-arm-kernel@lists.infradead.org,
        linux-kselftest@vger.kernel.org, kvmarm@lists.cs.columbia.edu
Subject: Re: [PATCH v11 17/40] arm64/sme: Implement ZA context switching
Message-ID: <YhTc2i/id7Ez52mN@arm.com>
References: <20220207152109.197566-1-broonie@kernel.org>
 <20220207152109.197566-18-broonie@kernel.org>
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On Mon, Feb 07, 2022 at 03:20:46PM +0000, Mark Brown wrote:
> Allocate space for storing ZA on first access to SME and use that to save
> and restore ZA state when context switching. We do this by using the vector
> form of the LDR and STR ZA instructions, these do not require streaming
> mode and have implementation recommendations that they avoid contention
> issues in shared SMCU implementations.
> 
> Since ZA is architecturally guaranteed to be zeroed when enabled we do not
> need to explicitly zero ZA, either we will be restoring from a saved copy
> or trapping on first use of SME so we know that ZA must be disabled.
> 
> Signed-off-by: Mark Brown <broonie@kernel.org>

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