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Date:   Thu, 12 Jan 2023 11:34:08 +0100
From:   Borislav Petkov <bp@alien8.de>
To:     Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Cc:     Breno Leitao <leitao@debian.org>, tglx@linutronix.de,
        mingo@redhat.com, dave.hansen@linux.intel.com, hpa@zytor.com,
        jpoimboe@kernel.org, peterz@infradead.org, x86@kernel.org,
        cascardo@canonical.com, leit@meta.com, kexec@lists.infradead.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3] x86/bugs: Explicitly clear speculative MSR bits
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 <20230112070037.q6cg23tn57onmxfi@desk>
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On Wed, Jan 11, 2023 at 11:00:37PM -0800, Pawan Gupta wrote:
> > SPEC_CTRL_RRSBA_DIS_S is a disable bit and I presume it needs to stay enabled.
> 
> The mitigation is enabled when this bit is set. When set, it prevents RET
> target to be predicted from alternate predictors (BTB). This should stay
> 0, unless enabled by a mitigation mode.
> 
> > Only when spec_ctrl_disable_kernel_rrsba() runs. And I'd say perf-wise it
> > doesn't cost that much...
> 
> I guess this doesn't matter now, because this patch is resetting it by
> default that keeps the mitigation disabled with no perf impact.

Ok, lemme queue it then.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette