linux-kernel - Re: [PATCH v2] arm64: spectre: increase parameters that can be used to turn off bhb mitigation individually

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Message-ID: <20220907162952.GC30558@willie-the-truck>
Date:   Wed, 7 Sep 2022 17:29:53 +0100
From:   Will Deacon <will@...nel.org>
To:     Catalin Marinas <catalin.marinas@....com>
Cc:     Liu Song <liusong@...ux.alibaba.com>, james.morse@....com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] arm64: spectre: increase parameters that can be used
 to turn off bhb mitigation individually

On Wed, Sep 07, 2022 at 03:29:05PM +0100, Catalin Marinas wrote:
> On Fri, Aug 26, 2022 at 07:40:50PM +0800, Liu Song wrote:
> > From: Liu Song <liusong@...ux.alibaba.com>
> > 
> > In our environment, it was found that the mitigation BHB has a great
> > impact on the benchmark performance. For example, in the lmbench test,
> > the "process fork && exit" test performance drops by 20%.
> > So it is necessary to have the ability to turn off the mitigation
> > individually through cmdline, thus avoiding having to compile the
> > kernel by adjusting the config.
> > 
> > Signed-off-by: Liu Song <liusong@...ux.alibaba.com>
> 
> If people want to disable this mitigation and know what they are doing,
> I have no objection:
> 
> Acked-by: Catalin Marinas <catalin.marinas@....com>

Thanks!

> (I guess that's more like 6.1 material)

Yup, agreed. I take it you'll pick it up, then?

Will