linux-kernel - Re: [PATCH v5 08/10] arm64: Always enable ssb vulnerability detection

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Message-ID: <5c76075d-1889-ff75-0567-f3e2df7079f4@foss.arm.com>
Date:   Fri, 1 Mar 2019 01:02:35 -0600
From:   Andre Przywara <andre.przywara@....com>
To:     Jeremy Linton <jeremy.linton@....com>,
        linux-arm-kernel@...ts.infradead.org
Cc:     catalin.marinas@....com, will.deacon@....com, marc.zyngier@....com,
        suzuki.poulose@....com, Dave.Martin@....com,
        shankerd@...eaurora.org, julien.thierry@....com,
        mlangsdo@...hat.com, stefan.wahren@....com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 08/10] arm64: Always enable ssb vulnerability detection

Hi,

On 2/26/19 7:05 PM, Jeremy Linton wrote:
> The ssb detection logic is necessary regardless of whether
> the vulnerability mitigation code is built into the kernel.
> Break it out so that the CONFIG option only controls the
> mitigation logic and not the vulnerability detection.
> 
> Signed-off-by: Jeremy Linton <jeremy.linton@....com>
> ---
>   arch/arm64/include/asm/cpufeature.h |  4 ----
>   arch/arm64/kernel/cpu_errata.c      | 11 +++++++----
>   2 files changed, 7 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
> index dfcfba725d72..c2b60a021437 100644
> --- a/arch/arm64/include/asm/cpufeature.h
> +++ b/arch/arm64/include/asm/cpufeature.h
> @@ -628,11 +628,7 @@ static inline int arm64_get_ssbd_state(void)
>   #endif
>   }
>   
> -#ifdef CONFIG_ARM64_SSBD
>   void arm64_set_ssbd_mitigation(bool state);
> -#else
> -static inline void arm64_set_ssbd_mitigation(bool state) {}
> -#endif
>   
>   extern int do_emulate_mrs(struct pt_regs *regs, u32 sys_reg, u32 rt);
>   
> diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
> index 0f6e8f5d67bc..5f5611d17dc1 100644
> --- a/arch/arm64/kernel/cpu_errata.c
> +++ b/arch/arm64/kernel/cpu_errata.c
> @@ -276,7 +276,6 @@ static int detect_harden_bp_fw(void)
>   	return 1;
>   }
>   
> -#ifdef CONFIG_ARM64_SSBD
>   DEFINE_PER_CPU_READ_MOSTLY(u64, arm64_ssbd_callback_required);
>   
>   int ssbd_state __read_mostly = ARM64_SSBD_KERNEL;
> @@ -347,6 +346,7 @@ void __init arm64_enable_wa2_handling(struct alt_instr *alt,
>   		*updptr = cpu_to_le32(aarch64_insn_gen_nop());
>   }
>   
> +#ifdef CONFIG_ARM64_SSBD
>   void arm64_set_ssbd_mitigation(bool state)
>   {
>   	if (this_cpu_has_cap(ARM64_SSBS)) {
> @@ -371,6 +371,12 @@ void arm64_set_ssbd_mitigation(bool state)
>   		break;
>   	}
>   }
> +#else
> +void arm64_set_ssbd_mitigation(bool state)
> +{
> +	pr_info_once("SSBD, disabled by kernel configuration\n");

Is there a stray comma or is the continuation of some previous printout?

Regardless of that it looks good and compiles with both 
CONFIG_ARM64_SSBD defined or not:

Reviewed-by: Andre Przywara <andre.przywara@....com>

Cheers,
Andre.

> +}
> +#endif	/* CONFIG_ARM64_SSBD */
>   
>   static bool has_ssbd_mitigation(const struct arm64_cpu_capabilities *entry,
>   				    int scope)
> @@ -468,7 +474,6 @@ static bool has_ssbd_mitigation(const struct arm64_cpu_capabilities *entry,
>   
>   	return required;
>   }
> -#endif	/* CONFIG_ARM64_SSBD */
>   
>   static void __maybe_unused
>   cpu_enable_cache_maint_trap(const struct arm64_cpu_capabilities *__unused)
> @@ -760,14 +765,12 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
>   		ERRATA_MIDR_RANGE_LIST(arm64_harden_el2_vectors),
>   	},
>   #endif
> -#ifdef CONFIG_ARM64_SSBD
>   	{
>   		.desc = "Speculative Store Bypass Disable",
>   		.capability = ARM64_SSBD,
>   		.type = ARM64_CPUCAP_LOCAL_CPU_ERRATUM,
>   		.matches = has_ssbd_mitigation,
>   	},
> -#endif
>   #ifdef CONFIG_ARM64_ERRATUM_1188873
>   	{
>   		/* Cortex-A76 r0p0 to r2p0 */
>