Re: [PATCH v7 20/24] iommu: Require a default_domain for all iommu drivers

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On Wed, Aug 23, 2023 at 01:47:34PM -0300, Jason Gunthorpe wrote:
> At this point every iommu driver will cause a default_domain to be
> selected, so we can finally remove this gap from the core code.
> The following table explains what each driver supports and what the
> resulting default_domain will be:
>                                         ops->defaut_domain
>                     IDENTITY   DMA  PLATFORM    v      ARM32          dma-iommu  ARCH
> amd/iommu.c             Y       Y                       N/A             either
> apple-dart.c            Y       Y                       N/A             either
> arm-smmu.c              Y       Y                       IDENTITY        either
> qcom_iommu.c            G       Y                       IDENTITY        either
> arm-smmu-v3.c           Y       Y                       N/A             either
> exynos-iommu.c          G       Y                       IDENTITY        either
> fsl_pamu_domain.c                       Y       Y       N/A             N/A     PLATFORM
> intel/iommu.c           Y       Y                       N/A             either
> ipmmu-vmsa.c            G       Y                       IDENTITY        either
> msm_iommu.c             G                               IDENTITY        N/A
> mtk_iommu.c             G       Y                       IDENTITY        either
> mtk_iommu_v1.c          G                               IDENTITY        N/A
> omap-iommu.c            G                               IDENTITY        N/A
> rockchip-iommu.c        G       Y                       IDENTITY        either
> s390-iommu.c                            Y       Y       N/A             N/A     PLATFORM
> sprd-iommu.c                    Y                       N/A             DMA
> sun50i-iommu.c          G       Y                       IDENTITY        either
> tegra-smmu.c            G       Y                       IDENTITY        IDENTITY
> virtio-iommu.c          Y       Y                       N/A             either
> spapr                                   Y       Y       N/A             N/A     PLATFORM
>  * G means ops->identity_domain is used
>  * N/A means the driver will not compile in this configuration
> ARM32 drivers select an IDENTITY default domain through either the
> ops->identity_domain or directly requesting an IDENTIY domain through
> alloc_domain().
> In ARM64 mode tegra-smmu will still block the use of dma-iommu.c and
> forces an IDENTITY domain.
> S390 uses a PLATFORM domain to represent when the dma_ops are set to the
> s390 iommu code.
> fsl_pamu uses an PLATFORM domain.
> POWER SPAPR uses PLATFORM and blocking to enable its weird VFIO mode.
> The x86 drivers continue unchanged.
> After this patch group->default_domain is only NULL for a short period
> during bus iommu probing while all the groups are constituted. Otherwise
> it is always !NULL.
> This completes changing the iommu subsystem driver contract to a system
> where the current iommu_domain always represents some form of translation
> and the driver is continuously asserting a definable translation mode.
> It resolves the confusion that the original ops->detach_dev() caused
> around what translation, exactly, is the IOMMU performing after
> detach. There were at least three different answers to that question in
> the tree, they are all now clearly named with domain types.
> Tested-by: Heiko Stuebner <heiko@xxxxxxxxx>
> Tested-by: Niklas Schnelle <schnelle@xxxxxxxxxxxxx>
> Tested-by: Steven Price <steven.price@xxxxxxx>
> Tested-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> Tested-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
> Reviewed-by: Lu Baolu <>
> Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
> ---
>  drivers/iommu/iommu.c | 22 +++++++---------------
>  1 file changed, 7 insertions(+), 15 deletions(-)

Reviewed-by: Jerry Snitselaar <jsnitsel@xxxxxxxxxx>

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