linux-kernel - Re: [PATCH v2] x86/bugs: Break down mitigations configurations

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Message-ID: <20230621194101.bmwesljror2yqjxx@desk>
Date:   Wed, 21 Jun 2023 12:41:01 -0700
From:   Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
To:     Breno Leitao <leitao@...ian.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...nel.org>, leit@...com,
        "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" 
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] x86/bugs: Break down mitigations configurations

On Wed, Jun 21, 2023 at 11:36:53AM -0700, Breno Leitao wrote:
> On Wed, Jun 21, 2023 at 10:31:35AM -0700, Pawan Gupta wrote:
> > On Wed, Jun 21, 2023 at 08:54:17AM -0700, Breno Leitao wrote:
> > > On Tue, Jun 20, 2023 at 05:13:27PM -0700, Pawan Gupta wrote:
> > > > On Fri, Jun 16, 2023 at 09:48:50AM -0700, Breno Leitao wrote:
> > > > > There is no way to disable MDS, TAA, MMIO Stale data mitigation today at
> > > > > compilation time. These mitigations are enabled even if
> > > > > CONFIG_SPECULATION_MITIGATIONS is unset.
> > > > > 
> > > > > Create a new KCONFIG option for each mitigation under
> > > > > CONFIG_SPECULATION_MITIGATIONS that allows these
> > > > > mitigations to be disabled by default at compilation time.
> > > > 
> > > > I don't think all mitigations are still controllable at build-time e.g.
> > > > spectre_v2 eIBRS mitigation will still be deployed irrespective of the
> > > > config.
> > > 
> > > Right. This patchset only cares about MDS, TAA and MMIO. I am more than
> > > happy to send a new patch to also disable spectre_v2 eIBRS.
> > 
> > What about Retbleed, L1TF, SRBDS etc? I thought the goal is to control
> > all speculation mitigations?
> > 
> > To be consistent CONFIG_SPECULATION_MITIGATIONS should control all
> > speculation mitigations.
> 
> If I understand where you want to go, you think we should create a
> single patchset that creates a CONFIG_<MITIGATION> for each mitigation,
> and move get it under CONFIG_SPECULATION_MITIGATIONS.

Yes, a single series (or a patch) that adds config for each mitigation
would be good.