[PATCH v5 0/4] iommu/s390: add support for IOMMU passthrough

Matthew Rosato
2025-02-12T21:34:35Z

This series introduces the ability for certain devices on s390 to bypass
a layer of IOMMU via the iommu.passthrough=1 option. In order to enable
this, the concept of an identity domain is added to s390-iommu. On s390,
IOMMU passthrough is only allowed if indicated via a special bit in s390
CLP data for the associated device group, otherwise we must fall back to
dma-iommu.

Changes for v5:
- Fixup error checking for bus_dma_region size
- Add review/test tags

Changes for v4:
- Additional patch to handle IOAT registration within s390-iommu. This
fixes an issue with re-registration of identity domain during events
like zpci_hot_reset_device
- Fixup page alignment for bus_dma_region setup
- Dropped a few review/test tags due to above changes

Changes for v3:
- Rebase onto 6.13
- fixed bus_dma_region size (Niklas)

Changes for v2:
- Remove ARCH_HAS_PHYS_TO_DMA, use bus_dma_region
- Remove use of def_domain_type, use 1 of 2 ops chosen at init

Matthew Rosato (4):
s390/pci: check for relaxed translation capability
s390/pci: store DMA offset in bus_dma_region
iommu/s390: handle IOAT registration based on domain
iommu/s390: implement iommu passthrough via identity domain

arch/s390/include/asm/pci.h | 4 +-
arch/s390/include/asm/pci_clp.h | 4 +-
arch/s390/kvm/pci.c | 17 +---
arch/s390/pci/pci.c | 35 ++++----
arch/s390/pci/pci_bus.c | 25 ++++++
arch/s390/pci/pci_clp.c | 1 +
arch/s390/pci/pci_sysfs.c | 11 +--
drivers/iommu/s390-iommu.c | 138 ++++++++++++++++++++++++++------
8 files changed, 168 insertions(+), 67 deletions(-)

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2.48.1