linux-kernel - Re: [PATCH 04/14] arm64: Add ARCH_WORKAROUND

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Message-ID: <0f980dce-170e-1d43-5927-c5d508839001@arm.com>
Date:   Wed, 23 May 2018 11:06:08 +0100
From:   Julien Grall <julien.grall@....com>
To:     Marc Zyngier <marc.zyngier@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kvmarm@...ts.cs.columbia.edu
Cc:     Kees Cook <keescook@...omium.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Andy Lutomirski <luto@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 04/14] arm64: Add ARCH_WORKAROUND_2 probing

Hi Marc,

On 05/22/2018 04:06 PM, Marc Zyngier wrote:
> As for Spectre variant-2, we rely on SMCCC 1.1 to provide the
> discovery mechanism for detecting the SSBD mitigation.
> 
> A new capability is also allocated for that purpose, and a
> config option.
> 
> Signed-off-by: Marc Zyngier <marc.zyngier@....com>
> ---
>   arch/arm64/Kconfig               |  9 ++++++
>   arch/arm64/include/asm/cpucaps.h |  3 +-
>   arch/arm64/kernel/cpu_errata.c   | 69 ++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 80 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index eb2cf4938f6d..b2103b4df467 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -938,6 +938,15 @@ config HARDEN_EL2_VECTORS
>   
>   	  If unsure, say Y.
>   
> +config ARM64_SSBD
> +	bool "Speculative Store Bypass Disable" if EXPERT
> +	default y
> +	help
> +	  This enables mitigation of the bypassing of previous stores
> +	  by speculative loads.
> +
> +	  If unsure, say Y.
> +
>   menuconfig ARMV8_DEPRECATED
>   	bool "Emulate deprecated/obsolete ARMv8 instructions"
>   	depends on COMPAT
> diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
> index bc51b72fafd4..5b2facf786ba 100644
> --- a/arch/arm64/include/asm/cpucaps.h
> +++ b/arch/arm64/include/asm/cpucaps.h
> @@ -48,7 +48,8 @@
>   #define ARM64_HAS_CACHE_IDC			27
>   #define ARM64_HAS_CACHE_DIC			28
>   #define ARM64_HW_DBM				29
> +#define ARM64_SSBD			30

NIT: Could you indent 30 the same way as the other number?

Reviewed-by: Julien Grall <julien.grall@....com>

Cheers,

-- 
Julien Grall