linux-kernel - Re: [PATCH 0/4] firmware: Add support for Qualcomm UEFI Secure Application

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Message-ID: <20220725192705.GA2536409-robh@kernel.org>
Date:   Mon, 25 Jul 2022 13:27:05 -0600
From:   Rob Herring <robh@...nel.org>
To:     Maximilian Luz <luzmaximilian@...il.com>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Steev Klimaszewski <steev@...i.org>,
        Shawn Guo <shawn.guo@...aro.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Cristian Marussi <cristian.marussi@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-arm-msm@...r.kernel.org, linux-efi@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/4] firmware: Add support for Qualcomm UEFI Secure
 Application

On Sun, Jul 24, 2022 at 12:49:45AM +0200, Maximilian Luz wrote:
> On modern Qualcomm platforms, access to EFI variables is restricted to
> the secure world / TrustZone, i.e. the Trusted Execution Environment
> (TrEE or TEE) as Qualcomm seems to call it. To access EFI variables, we
> therefore need to talk to the UEFI Secure Application (uefisecapp),
> residing in the TrEE.

The whole point of UEFI is providing a standard interface. Why can't the 
UEFI implementation call the TEE itself?

I'm not sure custom interfaces is something we want.


> This series adds support for accessing EFI variables on those platforms.
> 
> To do this, we first need to add some SCM call functions used to manage
> and talk to Secure Applications. A very small subset of this interface
> is added in the second patch (whereas the first one exports the required
> functions for that). Interface specifications are extracted from [1].
> While this does not (yet) support re-entrant SCM calls (including
> callbacks and listeners), this is enough to talk to the aforementioned
> uefisecapp on a couple of platforms (I've tested this on a Surface Pro X
> and heard reports from Lenovo Flex 5G, Lenovo Thinkpad x13s, and Lenovo
> Yoga C630 devices).

What does Windows do on these devices? I'm surprised something like this 
would fly with Microsoft.

Rob