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

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Message-ID: <efd011693768994a40fade46d858dbf14384b538.camel@amazon.com>
Date:   Thu, 2 Apr 2020 22:23:50 +0000
From:   "Singh, Balbir" <sblbir@...zon.com>
To:     "tglx@...utronix.de" <tglx@...utronix.de>,
        "jpoimboe@...hat.com" <jpoimboe@...hat.com>
CC:     "keescook@...omium.org" <keescook@...omium.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "tony.luck@...el.com" <tony.luck@...el.com>,
        "benh@...nel.crashing.org" <benh@...nel.crashing.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "dave.hansen@...el.com" <dave.hansen@...el.com>
Subject: Re: [PATCH 0/3] arch/x86: Optionally flush L1D on context switch

On Thu, 2020-04-02 at 23:45 +0200, Thomas Gleixner wrote:
> CAUTION: This email originated from outside of the organization. Do not
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> 
> 
> 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. :)

I hope people don't go looking for aliens in there :) I'll write up some
documentation if that helps, starting with something simple.

Balbir

> 
> Thanks,
> 
>         tglx
>