linux-kernel - Re: [PATCH 0/5] FlexRM support in VFIO platform

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Message-ID: <0dc860ed-a40c-1bfd-f584-225807edb25b@arm.com>
Date:   Wed, 19 Jul 2017 11:57:24 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Anup Patel <anup.patel@...adcom.com>,
        Will Deacon <will.deacon@....com>,
        Joerg Roedel <joro@...tes.org>,
        Baptiste Reynal <b.reynal@...tualopensystems.com>,
        Alex Williamson <alex.williamson@...hat.com>
Cc:     Scott Branden <sbranden@...adcom.com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        iommu@...ts.linux-foundation.org, kvm@...r.kernel.org,
        bcm-kernel-feedback-list@...adcom.com
Subject: Re: [PATCH 0/5] FlexRM support in VFIO platform

On 19/07/17 10:33, Anup Patel wrote:
> This patchset primarily adds Broadcom FlexRM reset module for
> VFIO platform driver. We also have minor improvments in IOMMU
> and VFIO driver to allow VFIO no-IOMMU mode access to FlexRM.

I'm struggling to understand the IOMMU changes here - what's the
FlexRM's hardware relationship with the IOMMU, and how is it different
from any other device? Furthermore, if there *is* a relevant IOMMU
present, why would no-IOMMU mode need to be involved at all?

Robin.

> The patches are based on Linux-4.13-rc1 and can also be
> found at flexrm-vfio-v1 branch of
> https://github.com/Broadcom/arm64-linux.git
> 
> Anup Patel (5):
>   iommu: Add capability IOMMU_CAP_BYPASS
>   iommu/arm-smmu: add IOMMU_CAP_BYPASS to the ARM SMMU driver
>   iommu/arm-smmu-v3: add IOMMU_CAP_BYPASS to the ARM SMMUv3 driver
>   vfio: Allow No-IOMMU mode for IOMMUs with bypass capability
>   vfio: platform: reset: Add Broadcom FlexRM reset module
> 
>  drivers/iommu/arm-smmu-v3.c                        |  2 +
>  drivers/iommu/arm-smmu.c                           |  2 +
>  drivers/vfio/platform/reset/Kconfig                |  9 +++
>  drivers/vfio/platform/reset/Makefile               |  1 +
>  .../vfio/platform/reset/vfio_platform_bcmflexrm.c  | 91 ++++++++++++++++++++++
>  drivers/vfio/vfio.c                                | 13 +++-
>  include/linux/iommu.h                              |  4 +
>  7 files changed, 119 insertions(+), 3 deletions(-)
>  create mode 100644 drivers/vfio/platform/reset/vfio_platform_bcmflexrm.c
>