linux-kernel - Re: [PATCH 1/1] x86/pti: Fix kernel warnings for pti= and nopti cmdline options.

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Message-ID: <3f9db8a8-0be0-fa21-7919-0d89e057f50e@cs.kuleuven.be>
Date:   Sat, 12 Aug 2023 08:53:59 -0700
From:   Jo Van Bulck <jo.vanbulck@...kuleuven.be>
To:     Dave Hansen <dave.hansen@...el.com>,
        Sohil Mehta <sohil.mehta@...el.com>,
        linux-kernel@...r.kernel.org, dave.hansen@...ux.intel.com,
        luto@...nel.org, peterz@...radead.org, mingo@...hat.com
Cc:     x86@...nel.org, bp@...en8.de, tglx@...utronix.de, hpa@...or.com
Subject: Re: [PATCH 1/1] x86/pti: Fix kernel warnings for pti= and nopti
 cmdline options.

On 11.08.23 17:08, Dave Hansen wrote:
> On 8/11/23 16:58, Sohil Mehta wrote:
>> I agree this doesn't have to be this complex. PTI_FORCE_AUTO is unnecessary.

> It's worth *ZERO* hassle.  The docs say:
> That's 100% unambiguous.
> 
> If you do "mitigations=off pti=auto", you might as well have done
> "pti=auto nopti" which is nonsense.
> 
> The kernel shouldn't fall over and die, but the user gets to hold the
> (undefined) pieces at this point.
> 
> Please let's not make this more complicated than it has to be.

Thank you both for the suggestions. I agree the code got overly complex 
and unnecessary when users are clearly passing conflicting options. So I 
prepared another patch iteration to largely revert back to the original 
proposed patch, i.e., *without* backwards compatible behavior when pti= 
nopti and mitigations=off are erroneously combined.

I'll post the new patch shortly.

Best,
Jo