[PATCH v2 0/5] iommu/s390: Further improvements

Niklas Schnelle
2022-11-09T14:29:26Z

Hi All,

This series of patches improves the s390 IOMMU driver. These improvements help
existing IOMMU users, mainly vfio-pci, but at the same time are also in
preparation of converting s390 to use the common DMA API implementation in
drivers/iommu/dma-iommu.c instead of its platform specific DMA API in
arch/s390/pci/pci_dma.c that sidesteps the IOMMU driver to control the same
hardware interface directly.

Among the included changes patch 1 improves the robustness of switching IOMMU
domains and patch 2 adds the I/O TLB operations necessary for the DMA API
conversion. Patches 3, 4, and 5 aim to improve performance with patch 5 being
the most intrusive by removing the I/O translation table lock and using atomic
updates instead.

This series is based on the s390 branch of Joerg's IOMMU tree[0] that includes
the latest s390 IOMMU fixes. It is available for easy testing in the
iommu_improve_v2 branch with signed tag s390_iommu_improve_v2 of my
git.kernel.org tree[1].

Best regards,
Niklas Schnelle

Changes sinve v1:
- If an IOTLB flush fails for one device don't skip the flush for other devices.
This is also needed when RCU readers try to flush a detached device. (Jason)
- Free a domain's IOMMU translation table via call_rcu() (Jason)

[0] https://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu.git/log/?h=s390
[1] https://git.kernel.org/pub/scm/linux/kernel/git/niks/linux.git/

Niklas Schnelle (5):
iommu/s390: Make attach succeed even if the device is in error state
iommu/s390: Add I/O TLB ops
iommu/s390: Use RCU to allow concurrent domain_list iteration
iommu/s390: Optimize IOMMU table walking
s390/pci: use lock-free I/O translation updates

arch/s390/include/asm/pci.h | 4 +-
arch/s390/kvm/pci.c | 6 +-
arch/s390/pci/pci.c | 13 +--
arch/s390/pci/pci_dma.c | 77 +++++++++------
drivers/iommu/s390-iommu.c | 184 ++++++++++++++++++++++++------------
5 files changed, 185 insertions(+), 99 deletions(-)

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2.34.1