From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Babu Moger <babu.moger@amd.com>
Cc: "Moger, Babu" <bmoger@amd.com>,
bp@alien8.de, bsd@redhat.com, corbet@lwn.net, hpa@zytor.com,
linux-kernel@vger.kernel.org, mingo@redhat.com,
tglx@linutronix.de, x86@kernel.org
Subject: Re: [v6 1/1] x86/bugs: Implement mitigation for Predictive Store
Date: Wed, 8 Sep 2021 11:20:47 -0700 [thread overview]
Message-ID: <20210908182047.lcor52bjzrt35gsq@treble> (raw)
In-Reply-To: <35a32225-25d3-88eb-f427-14c93c38c97b@amd.com>
On Tue, Sep 07, 2021 at 06:15:53PM -0500, Babu Moger wrote:
> >>> Because trying to give them separate interfaces, when PSF disable is
> >>> intertwined with SSB disable in hardware, is awkward and confusing. And
> >>> the idea of adding another double-negative interface (disable=off!),
> >>> just because a vulnerability is considered to be a CPU "feature", isn't
> >>> very appetizing.
> >>>
> >>> So instead of adding a new double-negative interface, which only *half*
> >>> works due to the ssb_disable dependency, and which is guaranteed to
> >>> further confuse users, and which not even be used in the real world
> >>> except possibly by confused users...
> >>>
> >>> I'm wondering if we can just start out with the simplest possible
> >>> approach: don't change any code and instead just document the fact that
> >>> "spec_store_bypass_disable=" also affects PSF.
> >>>
> >>> Then, later on, if a real-world need is demonstrated, actual code could
> >>> be added to support disabling PSF independently (but of course it would
> >>> never be fully independent since PSF disable is forced by SSB disable).
> >>
> >> Do you mean for now keep only 'on' and 'auto' and remove "off"?
> >
> > No, since PSF can already be mitigated with SSBD today, I'm suggesting
> > that all code be removed from the patch and instead just update the
> > documentation.
> >
>
> Hmm Interesting..
> Just updating the documentation and without giving interface to enable or
> disable will not be a much of a value add.
It's also not a value add to create controls and added complexity for a
feature which nobody needs. There's no harm in starting out with the
simplest possible solution, which is no code at all.
Code can always be added later if really needed...
--
Josh
next prev parent reply other threads:[~2021-09-08 18:20 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-17 22:00 [v6 0/1] Introduce support for PSF control Ramakrishna Saripalli
2021-05-17 22:00 ` [v6 1/1] x86/bugs: Implement mitigation for Predictive Store Forwarding Ramakrishna Saripalli
2021-05-18 2:55 ` Randy Dunlap
2021-05-18 12:27 ` Saripalli, RK
2021-05-18 20:35 ` Pawan Gupta
2021-05-19 5:38 ` Pawan Gupta
2021-05-19 13:19 ` Saripalli, RK
2021-05-19 5:50 ` Pawan Gupta
2021-09-01 20:20 ` [v6 1/1] x86/bugs: Implement mitigation for Predictive Store Babu Moger
2021-09-01 20:30 ` Babu Moger
2021-09-01 20:35 ` Babu Moger
2021-09-02 17:35 ` Pawan Gupta
2021-08-12 23:44 ` [v6 1/1] x86/bugs: Implement mitigation for Predictive Store Forwarding Josh Poimboeuf
2021-09-02 18:16 ` [v6 1/1] x86/bugs: Implement mitigation for Predictive Store Babu Moger
2021-09-03 0:07 ` Josh Poimboeuf
[not found] ` <dca004cf-bacc-1a1f-56d6-c06e8bec167a@amd.com>
2021-09-04 17:23 ` Josh Poimboeuf
2021-09-07 23:15 ` Babu Moger
2021-09-08 18:20 ` Josh Poimboeuf [this message]
2021-09-10 16:08 ` Babu Moger
2021-09-09 16:20 ` Bandan Das
2021-06-17 20:47 ` [v6 0/1] Introduce support for PSF control Saripalli, RK
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