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SubjectRe: [RFC PATCH v3 0/8] Add IOPF support for VFIO passthrough
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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@linaro.org/
> [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(-)
>

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