| Message ID | 20230310-dma_iommu-v8-0-2347dfbed7af@linux.ibm.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | iommu/dma: s390 DMA API conversion and optimized IOTLB flushing | expand |
On Fri, Mar 10, 2023 at 05:07:45PM +0100, Niklas Schnelle wrote: > Hi All, > > This patch series converts s390's PCI support from its platform specific DMA > API implementation in arch/s390/pci/pci_dma.c to the common DMA IOMMU layer. > The conversion itself is done in patches 3-4 with patch 2 providing the final > necessary IOMMU driver improvement to handle s390's special IOTLB flush > out-of-resource indication in virtualized environments. Patches 1-2 may be > applied independently. The conversion itself only touches the s390 IOMMU driver > and s390 arch code moving over remaining functions from the s390 DMA API > implementation. No changes to common code are necessary. It looks like this still hasn't made it upstream as of 6.4-rc1. What's holding this series up?
On Fri, 2023-05-12 at 07:29 -0700, Christoph Hellwig wrote: > On Fri, Mar 10, 2023 at 05:07:45PM +0100, Niklas Schnelle wrote: > > Hi All, > > > > This patch series converts s390's PCI support from its platform specific DMA > > API implementation in arch/s390/pci/pci_dma.c to the common DMA IOMMU layer. > > The conversion itself is done in patches 3-4 with patch 2 providing the final > > necessary IOMMU driver improvement to handle s390's special IOTLB flush > > out-of-resource indication in virtualized environments. Patches 1-2 may be > > applied independently. The conversion itself only touches the s390 IOMMU driver > > and s390 arch code moving over remaining functions from the s390 DMA API > > implementation. No changes to common code are necessary. > > It looks like this still hasn't made it upstream as of 6.4-rc1. What's > holding this series up? > I think with all the IOMMUFD work going on this got starved out of reviewer resources. I didn't have any open todos but I guess there is still some review needed around how the IOMMU driver tells the dma- iommu that it expects IOTLB flushes to be slow requiring a larger single flush queue. There was also a small conflict with commit 49a22aae7d9c ("iommu: Replace device_lock() with group->mutex") that prevented this from applying to current upstream so I've just now sent out a v9 rebased on v6.4-rc2. Thanks, Niklas
Hi All, This patch series converts s390's PCI support from its platform specific DMA API implementation in arch/s390/pci/pci_dma.c to the common DMA IOMMU layer. The conversion itself is done in patches 3-4 with patch 2 providing the final necessary IOMMU driver improvement to handle s390's special IOTLB flush out-of-resource indication in virtualized environments. Patches 1-2 may be applied independently. The conversion itself only touches the s390 IOMMU driver and s390 arch code moving over remaining functions from the s390 DMA API implementation. No changes to common code are necessary. After patch 4 the basic conversion is done and on our partitioning machine hypervisor LPAR performance matches or exceeds the existing code. When running under z/VM or KVM however, performance plummets to about half of the existing code due to a much higher rate of IOTLB flushes for unmapped pages. Due to the hypervisors use of IOTLB flushes to synchronize their shadow tables these are very expensive and minimizing them is key for regaining the performance loss. To this end patches 5-6 propose a new, single queue, IOTLB flushing scheme as an alternative to the existing per-CPU flush queues. Introducing an alternative scheme was also suggested by Robin Murphy[1]. In the previous RFC of this conversion Robin suggested reusing more of the existing queuing logic which I incorporated since v2. The single queue mode is introduced in patch 5 together with a new dma_iommu_options struct and tune_dma_iommu callback in IOMMU ops which allows IOMMU drivers to switch to a single flush queue. Then patch 6 enables variable queue sizes using power of 2 queue sizes and shift/mask to keep performance as close to the existing code as possible. The variable queue size and a variable timeout are added to the dma_iommu_options struct and utilized by s390 in the z/VM and KVM guest cases. As it is implemented in common code the single queue IOTLB flushing scheme can of course be used by other platforms with expensive IOTLB flushes. Particularly virtio-iommu may be a candidate. In a previous version I verified that the new scheme does work on my x86_64 Ryzen workstation by locally modifying iommu_subsys_init() to default to the single queue mode and verifying its use via "/sys/.../iommu_group/type". I did not find problems with an AMD GPU, Intel NIC (with SR-IOV and KVM pass-through), NVMes or any on board peripherals. For this version I switched to b4 prep/b4 send so this is now available with b4 generated tags in the b4/dma_iommu topic branch of my git.kernel.org repository[3]. And we also get base-commit, and change-id tags as well as PGP signed mails. NOTE: Due to the large drop in performance I think we should not merge the DMA API conversion (patch 4) until we have a more suited IOVA flushing scheme with similar improvements as the proposed changes. Best regards, Niklas [0] https://lore.kernel.org/linux-iommu/20221109142903.4080275-1-schnelle@linux.ibm.com/ [1] https://lore.kernel.org/linux-iommu/3e402947-61f9-b7e8-1414-fde006257b6f@arm.com/ [2] https://lore.kernel.org/linux-iommu/a8e778da-7b41-a6ba-83c3-c366a426c3da@arm.com/ [3] https://git.kernel.org/pub/scm/linux/kernel/git/niks/linux.git/ Changes sinve v7: - Add R-b from Matt - Rebase on v6.3-rc1 - Switched to b4 prep / b4 send adding base-commit, change-id, PGP signatures. For the cost of no per-patch change lists. Changes since v6: - Rebased on iommu-next branch (Matt) - No need for ops->set_platform_dma() anymore - Add gfp_t gfp parameters for page allocations - In patch 4 removed a superflous s390_domain->dma_table assignment - Added R-bs from Matt Changes since v5: - Instead of introducing a new IOMMU domain type utilize a new options mechanism that allows IOMMU drivers to tune the DMA IOMMU flushing (Jason, Robin) - The above reworks patches 5 and 6 - Dropped patch 7 as its functionality is no longer needed Changes since v4: - Picked up R-b's for patch 1, 2 and 3 - In patch 5 fixed iommu_group_store_type() mistakenly initializing DMA-SQ instead of DMA-FQ. This was caused by iommu_dma_init_fq() being called before domain->type is set, instead pass the type as paramater. This also closes a window where domain->type is still DMA while the FQ is already used. (Gerd) - Replaced a missed check for IOMMU_DOMAIN_DMA_FQ with the new generic __IOMMU_DOMAIN_DMA_LAZY in patch 5 - Made the ISM PCI Function Type a define (Matt) - Removed stale TODO comment (Matt) Changes since v3: - Reword commit message of patch 2 for more clarity - Correct typo in comment added by patch 2 (Alexandra) - Adapted signature of .iommu_tlb_sync mapo for sun50i IOMMU driver added in v6.2-rc1 (kernel test robot) - Add R-b from Alexandra for patch 1 Changes since v2: - Move the IOTLB out-of-resource handling into the IOMMU enabling it also for the IOMMU API (patch 2). This also makes this independent from the DMA API conversion (Robin, Jason). - Rename __IOMMU_DOMAIN_DMA_FQ to __IOMMU_DOMAIN_DMA_LAZY when introducing single queue flushing mode. - Make selecting between single and per-CPU flush queues an explicit IOMMU op (patch 7) Changes since RFC v1: - Patch 1 uses dma_set_mask_and_coherent() (Christoph) - Patch 3 now documents and allows the use of iommu.strict=0|1 on s390 and deprecates s390_iommu=strict while making it an alias. - Patches 5-7 completely reworked to reuse existing queue logic (Robin) - Added patch 4 to allow using iommu.strict=0|1 to override ops->def_domain_type. --- Niklas Schnelle (6): s390/ism: Set DMA coherent mask iommu: Allow .iotlb_sync_map to fail and handle s390's -ENOMEM return s390/pci: prepare is_passed_through() for dma-iommu s390/pci: Use dma-iommu layer iommu/dma: Allow a single FQ in addition to per-CPU FQs iommu/dma: Make flush queue sizes and timeout driver configurable Documentation/admin-guide/kernel-parameters.txt | 9 +- arch/s390/include/asm/pci.h | 7 - arch/s390/include/asm/pci_clp.h | 3 + arch/s390/include/asm/pci_dma.h | 121 +--- arch/s390/pci/Makefile | 2 +- arch/s390/pci/pci.c | 22 +- arch/s390/pci/pci_bus.c | 5 - arch/s390/pci/pci_debug.c | 12 +- arch/s390/pci/pci_dma.c | 735 ------------------------ arch/s390/pci/pci_event.c | 17 +- arch/s390/pci/pci_sysfs.c | 19 +- drivers/iommu/Kconfig | 4 +- drivers/iommu/amd/iommu.c | 5 +- drivers/iommu/apple-dart.c | 5 +- drivers/iommu/dma-iommu.c | 189 ++++-- drivers/iommu/dma-iommu.h | 4 +- drivers/iommu/intel/iommu.c | 5 +- drivers/iommu/iommu.c | 24 +- drivers/iommu/msm_iommu.c | 5 +- drivers/iommu/mtk_iommu.c | 5 +- drivers/iommu/s390-iommu.c | 435 +++++++++++++- drivers/iommu/sprd-iommu.c | 5 +- drivers/iommu/sun50i-iommu.c | 4 +- drivers/iommu/tegra-gart.c | 5 +- drivers/s390/net/ism_drv.c | 2 +- include/linux/iommu.h | 29 +- 26 files changed, 671 insertions(+), 1007 deletions(-) --- base-commit: fe15c26ee26efa11741a7b632e9f23b01aca4cc6 change-id: 20230310-dma_iommu-5e048c538647 Best regards,