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The IOMMU API has no concept of privilege so assumes all devices and mappings are equal, and indeed most non-CPU master devices on an AMBA interconnect make little use of the attribute bits on the bus thus by default perform unprivileged data accesses. Some devices, however, believe themselves more equal than others, such as programmable DMA controllers whose 'master' thread issues bus transactions marked as privileged instruction fetches, while the data accesses of its channel threads (under the control of Linux, at least) are marked as unprivileged. This poses a problem for implementing the DMA API on an IOMMU conforming to ARM VMSAv8, under which a page that is unprivileged-writeable is also implicitly privileged-execute-never. Given that, there is no one set of attributes with which iommu_map() can implement, say, dma_alloc_coherent() that will allow every possible type of access without something running into unexecepted permission faults. Fortunately the SMMU architecture provides a means to mitigate such issues by overriding the incoming attributes of a transaction; make use of that to strip the privileged/unprivileged status off incoming transactions, leaving just the instruction/data dichotomy which the IOMMU API does at least understand; Four states good, two states better. Signed-off-by: Robin Murphy <robin.murphy@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> |
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| .. | ||
| amd_iommu.c | ||
| amd_iommu_init.c | ||
| amd_iommu_proto.h | ||
| amd_iommu_types.h | ||
| amd_iommu_v2.c | ||
| arm-smmu-v3.c | ||
| arm-smmu.c | ||
| dma-iommu.c | ||
| dmar.c | ||
| exynos-iommu.c | ||
| fsl_pamu.c | ||
| fsl_pamu.h | ||
| fsl_pamu_domain.c | ||
| fsl_pamu_domain.h | ||
| intel-iommu.c | ||
| intel-svm.c | ||
| intel_irq_remapping.c | ||
| io-pgtable-arm.c | ||
| io-pgtable.c | ||
| io-pgtable.h | ||
| iommu-sysfs.c | ||
| iommu-traces.c | ||
| iommu.c | ||
| iova.c | ||
| ipmmu-vmsa.c | ||
| irq_remapping.c | ||
| irq_remapping.h | ||
| Kconfig | ||
| Makefile | ||
| msm_iommu.c | ||
| msm_iommu.h | ||
| msm_iommu_dev.c | ||
| msm_iommu_hw-8xxx.h | ||
| of_iommu.c | ||
| omap-iommu-debug.c | ||
| omap-iommu.c | ||
| omap-iommu.h | ||
| omap-iopgtable.h | ||
| rockchip-iommu.c | ||
| s390-iommu.c | ||
| tegra-gart.c | ||
| tegra-smmu.c | ||