linux-kernel - Re: [PATCH v2] dt-bindings: dvfs: Add support for generic performance domains

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Message-ID: <20201118211734.GA1827746@bogus>
Date:   Wed, 18 Nov 2020 15:17:34 -0600
From:   Rob Herring <robh@...nel.org>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     Hector Yuan <hector.yuan@...iatek.com>,
        linux-kernel@...r.kernel.org,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        devicetree@...r.kernel.org,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>
Subject: Re: [PATCH v2] dt-bindings: dvfs: Add support for generic
 performance domains

On Mon, 16 Nov 2020 18:13:56 +0000, Sudeep Holla 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
> 
> Cc: Rob Herring <robh+dt@...nel.org>
> Signed-off-by: Sudeep Holla <sudeep.holla@....com>
> ---
>  .../bindings/dvfs/performance-domain.yaml     | 76 +++++++++++++++++++
>  1 file changed, 76 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/dvfs/performance-domain.yaml
> 
> v1[1]->v2:
> 	- Changed to Dual License
> 	- Added select: true, enum for #performance-domain-cells and
> 	  $ref for performance-domain
> 	- Changed the example to use real existing compatibles instead
> 	  of made-up ones
> 
> [1] https://lore.kernel.org/lkml/20201105173539.1426301-1-sudeep.holla@arm.com
> 


My bot found errors running 'make dt_binding_check' on your patch:

yamllint warnings/errors:

dtschema/dtc warnings/errors:
/builds/robherring/linux-dt-review/Documentation/devicetree/bindings/ata/pata-common.example.dt.yaml: /: '#performance-domain-cells' is a required property
	From schema: /builds/robherring/linux-dt-review/Documentation/devicetree/bindings/dvfs/performance-domain.yaml
/builds/robherring/linux-dt-review/Documentation/devicetree/bindings/ata/sata-common.example.dt.yaml: /: '#performance-domain-cells' is a required property
	From schema: /builds/robherring/linux-dt-review/Documentation/devicetree/bindings/dvfs/performance-domain.yaml
/builds/robherring/linux-dt-review/Documentation/devicetree/bindings/ata/allwinner,sun8i-r40-ahci.example.dt.yaml: /: '#performance-domain-cells' is a required property
	From schema: /builds/robherring/linux-dt-review/Documentation/devicetree/bindings/dvfs/performance-domain.yaml
/builds/robherring/linux-dt-review/Documentation/devicetree/bindings/ata/allwinner,sun8i-r40-ahci.example.dt.yaml: example-0: '#performance-domain-cells' is a required property
	From schema: /builds/robherring/linux-dt-review/Documentation/devicetree/bindings/dvfs/performance-domain.yaml
/builds/robherring/linux-dt-review/Documentation/devicetree/bindings/ata/allwinner,sun8i-r40-ahci.example.dt.yaml: sata@...8000: '#performance-domain-cells' is a required property
	From schema: /builds/robherring/linux-dt-review/Documentation/devicetree/bindings/dvfs/performance-domain.yaml
/builds/robherring/linux-dt-review/Documentation/devicetree/bindings/ata/imx-sata.example.dt.yaml: /: '#performance-domain-cells' is a required property
	From schema: /builds/robherring/linux-dt-review/Documentation/devicetree/bindings/dvfs/performance-domain.yaml

and on and on...