linux-kernel - Re: [PATCH 0/3] arch/x86: Optionally flush L1D on context switch

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Message-ID: <875zehmujm.fsf@nanos.tec.linutronix.de>
Date:   Thu, 02 Apr 2020 23:45:01 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Josh Poimboeuf <jpoimboe@...hat.com>,
        "Singh\, Balbir" <sblbir@...zon.com>
Cc:     "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
        "tony.luck\@intel.com" <tony.luck@...el.com>,
        "keescook\@chromium.org" <keescook@...omium.org>,
        "benh\@kernel.crashing.org" <benh@...nel.crashing.org>,
        "x86\@kernel.org" <x86@...nel.org>,
        "dave.hansen\@intel.com" <dave.hansen@...el.com>
Subject: Re: [PATCH 0/3] arch/x86: Optionally flush L1D on context switch

Josh Poimboeuf <jpoimboe@...hat.com> writes:
> On Thu, Apr 02, 2020 at 08:35:46PM +0000, Singh, Balbir wrote:
>> Yes, that CVE the motivation, the mitigation for CVE-2020-0550 does suggest
>> flushing the cache on context switch. But in general, as we begin to find more
>> ways of evicting data or snopping data, a generic mechanism is more useful and
>> that is why I am making it an opt-in.
>
> Ok.  I think it would be a good idea to expand on that justification
> more precisely in the commit message.  That would help both reviewers of
> the code and users of the new option understand what level of paranoia
> they're opting in to :-)

The commit message is mostly useful for reviewers and people who have to
do code archeaology. 

Documentation/admin-guide/hw-vuln/ has plenty of space to host a
document with explanations. paranoia.rst comes to my mind. :)

Thanks,

        tglx