Re: [PATCH v2 00/12] VIRTIO-IOMMU/VFIO: Don't assume 64b IOVA space

[YangHang Liu]

The original issue I found : After starting a VM which has two ice PFs
and a virtio-iommu device, qemu-kvm and VM guest dmesg throw lots of
duplicate VFIO_MAP_DMA errors

After testing with Eric's build, the  original issue is gone and the
Tier1 regression test against ice PF and virtio iommu device gets PASS
as well.

Tested-by: Yanghang Liu <yanghliu@redhat.com>



On Wed, Sep 13, 2023 at 4:06 PM Eric Auger <eric.auger@redhat.com> wrote:
>
> On x86, when assigning VFIO-PCI devices protected with virtio-iommu
> we encounter the case where the guest tries to map IOVAs beyond 48b
> whereas the physical VTD IOMMU only supports 48b. This ends up with
> VFIO_MAP_DMA failures at qemu level because at kernel level,
> vfio_iommu_iova_dma_valid() check returns false on vfio_map_do_map().
>
> This is due to the fact the virtio-iommu currently unconditionally
> exposes an IOVA range of 64b through its config input range fields.
>
> This series removes this assumption by retrieving the usable IOVA
> regions through the VFIO_IOMMU_TYPE1_INFO_CAP_IOVA_RANGE UAPI when
> a VFIO device is attached. This info is communicated to the
> virtio-iommu memory region, transformed into the inversed info, ie.
> the host reserved IOVA regions. Then those latter are combined with the
> reserved IOVA regions set though the virtio-iommu reserved-regions
> property. That way, the guest virtio-iommu driver, unchanged, is
> able to probe the whole set of reserved regions and prevent any IOVA
> belonging to those ranges from beeing used, achieving the original goal.
>
> Best Regards
>
> Eric
>
> This series can be found at:
> https://github.com/eauger/qemu/tree/virtio-iommu_geometry_v2
>
> History:
> v1 -> v2:
> - Remove "[PATCH 12/13] virtio-iommu: Resize memory region according
>   to the max iova info" which causes way too much trouble: trigger
>   a coredump in vhost, causes duplication of IOMMU notifiers causing
>   EEXIST vfio_dma_map errors, ... This looks like a bad usage of the
>   memory API so I prefer removing this from this series. So I was
>   also obliged to remove the vfio_find_hostwin() check in the case
>   of an IOMMU MR.
> - Let range_inverse_array() take low/high args instead of hardcoding
>   0, UINT64_MAX which both complexifies the algo and the tests.
> - Move range function description in header.
> - Check that if set_iova_ranges is called several times, new resv
>   regions are included in previous ones
>
> Eric Auger (12):
>   memory: Let ReservedRegion use Range
>   memory: Introduce memory_region_iommu_set_iova_ranges
>   vfio: Collect container iova range info
>   virtio-iommu: Rename reserved_regions into prop_resv_regions
>   virtio-iommu: Introduce per IOMMUDevice reserved regions
>   range: Introduce range_inverse_array()
>   virtio-iommu: Implement set_iova_ranges() callback
>   range: Make range_compare() public
>   util/reserved-region: Add new ReservedRegion helpers
>   virtio-iommu: Consolidate host reserved regions and property set ones
>   test: Add some tests for range and resv-mem helpers
>   vfio: Remove 64-bit IOVA address space assumption
>
>  include/exec/memory.h            |  30 +++-
>  include/hw/vfio/vfio-common.h    |   2 +
>  include/hw/virtio/virtio-iommu.h |   7 +-
>  include/qemu/range.h             |  14 ++
>  include/qemu/reserved-region.h   |  32 ++++
>  hw/core/qdev-properties-system.c |   9 +-
>  hw/vfio/common.c                 |  70 +++++++--
>  hw/virtio/virtio-iommu-pci.c     |   8 +-
>  hw/virtio/virtio-iommu.c         | 110 ++++++++++++--
>  softmmu/memory.c                 |  15 ++
>  tests/unit/test-resv-mem.c       | 251 +++++++++++++++++++++++++++++++
>  util/range.c                     |  51 ++++++-
>  util/reserved-region.c           |  94 ++++++++++++
>  hw/virtio/trace-events           |   1 +
>  tests/unit/meson.build           |   1 +
>  util/meson.build                 |   1 +
>  16 files changed, 655 insertions(+), 41 deletions(-)
>  create mode 100644 include/qemu/reserved-region.h
>  create mode 100644 tests/unit/test-resv-mem.c
>  create mode 100644 util/reserved-region.c
>
> --
> 2.41.0
>
>