linux-kernel - RE: [RFC][PATCH 06/17] x86/cpu: Add SRSO untrain to retbleed=

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Date:   Mon, 14 Aug 2023 15:45:22 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Peter Zijlstra' <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>
CC:     Josh Poimboeuf <jpoimboe@...nel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "David.Kaplan@....com" <David.Kaplan@....com>,
        "Andrew.Cooper3@...rix.com" <Andrew.Cooper3@...rix.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
Subject: RE: [RFC][PATCH 06/17] x86/cpu: Add SRSO untrain to retbleed=

From: Peter Zijlstra
> Sent: 12 August 2023 12:33
> 
> On Fri, Aug 11, 2023 at 12:27:48PM +0200, Borislav Petkov wrote:
> > On Thu, Aug 10, 2023 at 12:10:03PM -0400, Josh Poimboeuf wrote:
> > > I tend to agree that SRSO is a new issue and should have its own sysfs
> > > and cmdline options (though a separate CONFIG option is overkill IMO).
> >
> > Yeah, there's a patch floating around adding a config option for every
> > mitigation. Apparently people want to build-time disable them all.
> 
> So I really hate that .Kconfig explosion, that's the very last thing we
> need :-( More random options that can cause build time trouble.
> 
> I might see value in one knob that kills all speculation nonsense at
> build time, but not one per mitigation, that's maddness.

Or a very limited number of options for things that are
pretty separate.
Maybe the call/indirect jump are separate enough from the
return ones?

An one big KNOB to disable them all (DEPEND_ON !NO_MIGIGATIONS ?).

	David

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