Re: [PATCH v6 09/25] iommu: Allow an IDENTITY domain as the default_domain in ARM32
From: Baolu Lu <baolu.lu@linux.intel.com>
Date: 2023-08-14 04:33:29
Also in:
linux-arm-kernel, linux-arm-msm, linux-iommu, linux-mediatek, linux-rockchip, linux-s390, linux-samsung-soc, linux-sunxi, linux-tegra
On 2023/8/3 8:07, Jason Gunthorpe wrote:
Even though dma-iommu.c and CONFIG_ARM_DMA_USE_IOMMU do approximately the same stuff, the way they relate to the IOMMU core is quiet different. dma-iommu.c expects the core code to setup an UNMANAGED domain (of type IOMMU_DOMAIN_DMA) and then configures itself to use that domain. This becomes the default_domain for the group. ARM_DMA_USE_IOMMU does not use the default_domain, instead it directly allocates an UNMANAGED domain and operates it just like an external driver. In this case group->default_domain is NULL. If the driver provides a global static identity_domain then automatically use it as the default_domain when in ARM_DMA_USE_IOMMU mode. This allows drivers that implemented default_domain == NULL as an IDENTITY translation to trivially get a properly labeled non-NULL default_domain on ARM32 configs. With this arrangment when ARM_DMA_USE_IOMMU wants to disconnect from the device the normal detach_domain flow will restore the IDENTITY domain as the default domain. Overall this makes attach_dev() of the IDENTITY domain called in the same places as detach_dev(). This effectively migrates these drivers to default_domain mode. For drivers that support ARM64 they will gain support for the IDENTITY translation mode for the dma_api and behave in a uniform way. Drivers use this by setting ops->identity_domain to a static singleton iommu_domain that implements the identity attach. If the core detects ARM_DMA_USE_IOMMU mode then it automatically attaches the IDENTITY domain during probe. Drivers can continue to prevent the use of DMA translation by returning IOMMU_DOMAIN_IDENTITY from def_domain_type, this will completely prevent IOMMU_DMA from running but will not impact ARM_DMA_USE_IOMMU. This allows removing the set_platform_dma_ops() from every remaining driver. Remove the set_platform_dma_ops from rockchip and mkt_v1 as all it does is set an existing global static identity domain. mkt_v1 does not support IOMMU_DOMAIN_DMA and it does not compile on ARM64 so this transformation is safe. Tested-by: Steven Price<steven.price@arm.com> Tested-by: Marek Szyprowski<m.szyprowski@samsung.com> Tested-by: Nicolin Chen<redacted> Signed-off-by: Jason Gunthorpe<jgg@nvidia.com> --- drivers/iommu/iommu.c | 26 +++++++++++++++++++++++--- drivers/iommu/mtk_iommu_v1.c | 12 ------------ drivers/iommu/rockchip-iommu.c | 10 ---------- 3 files changed, 23 insertions(+), 25 deletions(-)
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com> Best regards, baolu