linux-kernel - Re: [PATCH v8 13/14] remoteproc: qcom: pas: Enable Secure PAS support with IOMMU managed by Linux

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Message-ID: <d7342610-c37b-4f5e-a2bc-1a683f9acf97@oss.qualcomm.com>
Date: Mon, 24 Nov 2025 12:31:47 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Mukesh Ojha <mukesh.ojha@....qualcomm.com>,
        Bjorn Andersson <andersson@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
 <conor+dt@...nel.org>,
        Manivannan Sadhasivam <mani@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>
Cc: linux-arm-msm@...r.kernel.org, linux-remoteproc@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 13/14] remoteproc: qcom: pas: Enable Secure PAS support
 with IOMMU managed by Linux

On 11/21/25 12:01 PM, Mukesh Ojha wrote:
> Most Qualcomm platforms feature Gunyah hypervisor, which typically
> handles IOMMU configuration. This includes mapping memory regions and
> device memory resources for remote processors by intercepting
> qcom_scm_pas_auth_and_reset() calls. These mappings are later removed
> during teardown. Additionally, SHM bridge setup is required to enable
> memory protection for both remoteproc metadata and its memory regions.
> When the aforementioned hypervisor is absent, the operating system must
> perform these configurations instead.
> 
> When Linux runs as the hypervisor (@ EL2) on a SoC, it will have its
> own device tree overlay file that specifies the firmware stream ID now
> managed by Linux for a particular remote processor. If the iommus
> property is specified in the remoteproc device tree node, it indicates
> that IOMMU configuration must be handled by Linux. In this case, the
> has_iommu flag is set for the remote processor, which ensures that the
> resource table, carveouts, and SHM bridge are properly configured before
> memory is passed to TrustZone for authentication. Otherwise, the
> has_iommu flag remains unset, which indicates default behavior.
> 
> Enables Secure PAS support for remote processors when IOMMU configuration
> is managed by Linux.
> 
> Signed-off-by: Mukesh Ojha <mukesh.ojha@....qualcomm.com>
> ---

[...]

> +	pas->pas_ctx->has_iommu = rproc->has_iommu;
> +	pas->dtb_pas_ctx->has_iommu = rproc->has_iommu;

Sorry if we've been there before, but I see that IOMMU-mapping happens
before ctx initialization.. can we drop this parameter and just use
device_iommu_mapped(ctx->dev) in qcom_scm_pas_prepare_and_auth_reset()?