On 2021/4/9 11:44, Shenming Lu wrote: > Hi, > > Requesting for your comments and suggestions. :-) Kind ping... > > The static pinning and mapping problem in VFIO and possible solutions > have been discussed a lot [1, 2]. One of the solutions is to add I/O > Page Fault support for VFIO devices. Different from those relatively > complicated software approaches such as presenting a vIOMMU that provides > the DMA buffer information (might include para-virtualized optimizations), > IOPF mainly depends on the hardware faulting capability, such as the PCIe > PRI extension or Arm SMMU stall model. What's more, the IOPF support in > the IOMMU driver has already been implemented in SVA [3]. So we add IOPF > support for VFIO passthrough based on the IOPF part of SVA in this series. > > We have measured its performance with UADK [4] (passthrough an accelerator > to a VM(1U16G)) on Hisilicon Kunpeng920 board (and compared with host SVA): > > Run hisi_sec_test... > - with varying sending times and message lengths > - with/without IOPF enabled (speed slowdown) > > when msg_len = 1MB (and PREMAP_LEN (in Patch 4) = 1): > slowdown (num of faults) > times VFIO IOPF host SVA > 1 63.4% (518) 82.8% (512) > 100 22.9% (1058) 47.9% (1024) > 1000 2.6% (1071) 8.5% (1024) > > when msg_len = 10MB (and PREMAP_LEN = 512): > slowdown (num of faults) > times VFIO IOPF > 1 32.6% (13) > 100 3.5% (26) > 1000 1.6% (26) > > History: > > v2 -> v3 > - Nit fixes. > - No reason to disable reporting the unrecoverable faults. (baolu) > - Maintain a global IOPF enabled group list. > - Split the pre-mapping optimization to be a separate patch. > - Add selective faulting support (use vfio_pin_pages to indicate the > non-faultable scope and add a new struct vfio_range to record it, > untested). (Kevin) > > v1 -> v2 > - Numerous improvements following the suggestions. Thanks a lot to all > of you. > > Note that PRI is not supported at the moment since there is no hardware. > > Links: > [1] Lesokhin I, et al. Page Fault Support for Network Controllers. In ASPLOS, > 2016. > [2] Tian K, et al. coIOMMU: A Virtual IOMMU with Cooperative DMA Buffer Tracking > for Efficient Memory Management in Direct I/O. In USENIX ATC, 2020. > [3] https://patchwork.kernel.org/project/linux-arm-kernel/cover/20210401154718.307519-1-jean-philippe@xxxxxxxxxx/ > [4] https://github.com/Linaro/uadk > > Thanks, > Shenming > > > Shenming Lu (8): > iommu: Evolve the device fault reporting framework > vfio/type1: Add a page fault handler > vfio/type1: Add an MMU notifier to avoid pinning > vfio/type1: Pre-map more pages than requested in the IOPF handling > vfio/type1: VFIO_IOMMU_ENABLE_IOPF > vfio/type1: No need to statically pin and map if IOPF enabled > vfio/type1: Add selective DMA faulting support > vfio: Add nested IOPF support > > .../iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c | 3 +- > drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 18 +- > drivers/iommu/iommu.c | 56 +- > drivers/vfio/vfio.c | 85 +- > drivers/vfio/vfio_iommu_type1.c | 1000 ++++++++++++++++- > include/linux/iommu.h | 19 +- > include/linux/vfio.h | 13 + > include/uapi/linux/iommu.h | 4 + > include/uapi/linux/vfio.h | 6 + > 9 files changed, 1181 insertions(+), 23 deletions(-) >
