linux-kernel - Re: [PATCH] x86/cpu: clear X86_BUG_SPECTRE

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Message-ID: <87h80wxsze.fsf@nanos.tec.linutronix.de>
Date:   Wed, 15 Jan 2020 23:19:49 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Tony W Wang-oc <TonyWWang-oc@...oxin.com>, mingo@...hat.com,
        bp@...en8.de, hpa@...or.com, x86@...nel.org,
        linux-kernel@...r.kernel.org
Cc:     DavidWang@...oxin.com, CooperYan@...oxin.com,
        QiyuanWang@...oxin.com, HerryYang@...oxin.com
Subject: Re: [PATCH] x86/cpu: clear X86_BUG_SPECTRE_V2 on Zhaoxin family 7 CPUs

Tony W Wang-oc <TonyWWang-oc@...oxin.com> writes:

> These CPUs are not affected by spectre_v2, so clear spectre_v2 bug flag
> in their specific initialization code.
>  
>  	if (cpu_has(c, X86_FEATURE_VMX))
>  		centaur_detect_vmx_virtcap(c);
> +
> +	if (c->x86 == 7) {
> +		setup_clear_cpu_cap(X86_BUG_SPECTRE_V2);
> +		clear_bit(X86_BUG_SPECTRE_V2, (unsigned long *)cpu_caps_set);

No. Please use cpu_vuln_whitelist. It exists for exactly this
purpose. You just need to extend it with a NO_SPECTRE_V2 bit.

Thanks,

        tglx