linux-kernel - Re: [PATCH v3 3/8] x86, lib: Add WBNOINVD helper functions

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Message-ID: <20250710143729.GL1613200@noisy.programming.kicks-ass.net>
Date: Thu, 10 Jul 2025 16:37:29 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Borislav Petkov <bp@...en8.de>
Cc: Sean Christopherson <seanjc@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
	Paolo Bonzini <pbonzini@...hat.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	dri-devel@...ts.freedesktop.org,
	Kevin Loughlin <kevinloughlin@...gle.com>,
	Tom Lendacky <thomas.lendacky@....com>,
	Kai Huang <kai.huang@...el.com>, Ingo Molnar <mingo@...nel.org>,
	Zheyun Shen <szy0127@...u.edu.cn>,
	Mingwei Zhang <mizhang@...gle.com>,
	Francesco Lavra <francescolavra.fl@...il.com>
Subject: Re: [PATCH v3 3/8] x86, lib: Add WBNOINVD helper functions

On Thu, Jul 10, 2025 at 01:29:02PM +0200, Borislav Petkov wrote:
> On Thu, May 22, 2025 at 04:37:27PM -0700, Sean Christopherson wrote:
> > diff --git a/arch/x86/lib/cache-smp.c b/arch/x86/lib/cache-smp.c
> > index 079c3f3cd32c..1789db5d8825 100644
> > --- a/arch/x86/lib/cache-smp.c
> > +++ b/arch/x86/lib/cache-smp.c
> > @@ -19,3 +19,14 @@ void wbinvd_on_all_cpus(void)
> >  	on_each_cpu(__wbinvd, NULL, 1);
> >  }
> >  EXPORT_SYMBOL(wbinvd_on_all_cpus);
> > +
> > +static void __wbnoinvd(void *dummy)
> > +{
> > +	wbnoinvd();
> > +}
> > +
> > +void wbnoinvd_on_all_cpus(void)
> > +{
> > +	on_each_cpu(__wbnoinvd, NULL, 1);
> > +}
> > +EXPORT_SYMBOL(wbnoinvd_on_all_cpus);
> 
> If there's no particular reason for the non-GPL export besides being
> consistent with the rest - yes, I did the change for wbinvd_on_all_cpus() but
> that was loooong time ago - I'd simply make this export _GPL.

Uhhhh, how about we use this fancy export to known modules only thing
for this?

These are typical things we do *NOT* want people to actually use.