linux-kernel - Re: [PATCH v4 2/5] cpu/speculation: Fix CPU mitigation defaults for !x86

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Date: Tue, 23 Apr 2024 22:35:11 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: Sean Christopherson <seanjc@...gle.com>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Daniel Sneddon <daniel.sneddon@...ux.intel.com>,
	Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Alexandre Chartre <alexandre.chartre@...cle.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Andrew Cooper <andrew.cooper3@...rix.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Nikolay Borisov <nik.borisov@...e.com>,
	KP Singh <kpsingh@...nel.org>, Waiman Long <longman@...hat.com>,
	Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...nel.org>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Michael Ellerman <mpe@...erman.id.au>,
	Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCH v4 2/5] cpu/speculation: Fix CPU mitigation defaults for
 !x86

On Tue, Apr 23, 2024 at 07:10:23AM -0700, Sean Christopherson wrote:
> On Fri, Apr 19, 2024, Sean Christopherson wrote:
> > On Fri, Apr 19, 2024, Josh Poimboeuf wrote:
> > > CPU speculative execution mitigations were inadvertently disabled on
> > > non-x86 arches by the following commit:
> > > 
> > >  f337a6a21e2f ("x86/cpu: Actually turn off mitigations by default for SPECULATION_MITIGATIONS=n")
> > > 
> > > Fix it by replacing CONFIG_SPECULATION_MITIGATIONS with a new generic
> > > CONFIG_CPU_MITIGATIONS option and moving the x86-specific mitigations to
> > > a separate menu which depends on CONFIG_CPU_MITIGATIONS.
> > 
> > Ah drat, I didn't check my mailbox until after Cc'ing Linus my own version[*].
> > 
> > I don't have a strong preference between the two, though I do think it's worth
> > nothing that this will (obvioulsy) allow disabling mitigations at compile time
> > on all architectures, which may or may not be desirable.
> > 
> > [*] https://lore.kernel.org/all/20240420000556.2645001-2-seanjc@google.com
> 
> Josh, when you get a chance, can you weigh in on my menu-preserving approach?
> 
> I want to get this resolved asap so that we're not scrambing on Friday again :-)

Yeah, yours looks good.  Lemme go ack.

-- 
Josh