linux-kernel - Re: [PATCH 1/5] x86/cpufeatures: Define feature bits to support mitigation of PSF

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Message-ID: <20210409201924.GJ15567@zn.tnic>
Date:   Fri, 9 Apr 2021 22:19:24 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     "Saripalli, RK" <rsaripal@....com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH 1/5] x86/cpufeatures: Define feature bits to support
 mitigation of PSF

On Fri, Apr 09, 2021 at 02:45:23PM -0500, Saripalli, RK wrote:
> Yes, these options should be fine for now.
> Like you said, if we get the need to add prctl and seccomp, I can always do that later.
> 
> What do you think auto should default to?. 
> In SSBD case, I believe auto defaults to prctl or seccomp.
> Since we will not have that here, we should choose something for auto.

Or not add it yet. Just have "on" and "off" for now.

Which begs the question should this be controllable by the mitigations=
switch too?

I wanna say, let's have people evaluate and play with it first and
we can add it to that switch later. As long as we don't change the
user-visible controls - if anything we'll be extending them later,
potentially - we should be fine usage-wise and from user visibility POV.

> All the other mitigation x86 mitigation code goes into kernel/cpu/bugs.c.
> I think psf_cmdline() or equivalent also belongs there and not in kernel/cpu/amd.c.

It being AMD-specific, it can dwell in amd.c initially.

Thx.

-- 
Regards/Gruss,
    Boris.

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