linux-kernel - Re: [PATCH v4] dt-bindings: dvfs: Add support for generic performance domains

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Date:   Wed, 19 May 2021 12:23:18 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     Rob Herring <robh@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        devicetree@...r.kernel.org, Sudeep Holla <sudeep.holla@....com>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Hector Yuan <hector.yuan@...iatek.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>
Subject: Re: [PATCH v4] dt-bindings: dvfs: Add support for generic
 performance domains

On Mon, May 17, 2021 at 02:17:05PM -0500, Rob Herring wrote:
> On Mon, May 17, 2021 at 10:55 AM Sudeep Holla <sudeep.holla@....com> wrote:
> >
> > The CLKSCREW attack [0] exposed security vulnerabilities in energy management
> > implementations where untrusted software had direct access to clock and
> > voltage hardware controls. In this attack, the malicious software was able to
> > place the platform into unsafe overclocked or undervolted configurations. Such
> > configurations then enabled the injection of predictable faults to reveal
> > secrets.
> >
> > Many Arm-based systems used to or still use voltage regulator and clock
> > frameworks in the kernel. These frameworks allow callers to independently
> > manipulate frequency and voltage settings. Such implementations can render
> > systems susceptible to this form of attack.
> >
> > Attacks such as CLKSCREW are now being mitigated by not having direct and
> > independent control of clock and voltage in the kernel and moving that
> > control to a trusted entity, such as the SCP firmware or secure world
> > firmware/software which are to perform sanity checking on the requested
> > performance levels, thereby preventing any attempted malicious programming.
> >
> > With the advent of such an abstraction, there is a need to replace the
> > generic clock and regulator bindings used by such devices with a generic
> > performance domains bindings.
> >
> > [0] https://www.usenix.org/conference/usenixsecurity17/technical-sessions/presentation/tang
> >
> > Link: https://lore.kernel.org/r/20201116181356.804590-1-sudeep.holla@arm.com
> > Cc: Rob Herring <robh+dt@...nel.org>
> > Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
> > Signed-off-by: Sudeep Holla <sudeep.holla@....com>
> 
> Reviewed-by: Rob Herring <robh@...nel.org>

Thanks Rob.

Viresh,

I noticed I haven't cc-ed linux-pm list, do you need me to post there or
are you happy to pick it up from here when Hector's mediatek cpufreq drivers
using this are ready to be merged ?

--
Regards,
Sudeep