linux-kernel - Re: [PATCH] iommu/arm-smmu: Use pm

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <9d3c78e9-db4f-4ffd-9097-f48e73d62c8d@oss.qualcomm.com>
Date: Tue, 27 Jan 2026 18:22:10 +0530
From: Akhil P Oommen <akhilpo@....qualcomm.com>
To: Prakash Gupta <prakash.gupta@....qualcomm.com>,
        Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>,
        Rob Clark <robin.clark@....qualcomm.com>,
        Connor Abbott <cwabbott0@...il.com>
Cc: linux-arm-msm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        iommu@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Pratyush Brahma <pratyush.brahma@....qualcomm.com>
Subject: Re: [PATCH] iommu/arm-smmu: Use pm_runtime in fault handlers

On 1/27/2026 5:41 PM, Prakash Gupta wrote:
> Commit d4a44f0750bb ("iommu/arm-smmu: Invoke pm_runtime across the driver")
> enabled pm_runtime for the arm-smmu device. On systems where the SMMU
> sits in a power domain, all register accesses must be done while the
> device is runtime-resumed to avoid unclocked register reads and
> potential NoC errors.
> 
> So far, this has not been an issue for most SMMU clients because
> stall-on-fault is enabled by default. While a translation fault is
> being handled, the SMMU stalls further translations for that context
> bank, so the fault handler would not race with a powered-down
> SMMU.
> 
> Adreno SMMU now disables stall-on-fault in the presence of fault
> storms to avoid saturating SMMU resources and hanging the GMU. With
> stall-on-fault disabled, the SMMU can generate faults while its power
> domain may no longer be enabled, which makes unclocked accesses to
> fault-status registers in the SMMU fault handlers possible.
> 
> Guard the context and global fault handlers with arm_smmu_rpm_get() /
> arm_smmu_rpm_put() so that all SMMU fault register accesses are done
> with the SMMU powered.
> 
> Fixes: b13044092c1e ("drm/msm: Temporarily disable stall-on-fault after a page fault")
> Co-developed-by: Pratyush Brahma <pratyush.brahma@....qualcomm.com>
> Signed-off-by: Pratyush Brahma <pratyush.brahma@....qualcomm.com>
> Signed-off-by: Prakash Gupta <prakash.gupta@....qualcomm.com>

Acked-by: Akhil P Oommen <akhilpo@....qualcomm.com>

-Akhil