Re: [PATCH v3 00/13] 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, Oct 18, 2023 at 9:45 PM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Wed, Oct 11, 2023 at 07:52:16PM +0200, Eric Auger wrote:
> > This applies on top of vfio-next:
> > https://github.com/legoater/qemu/, vfio-next branch
>
> virtio things make sense
>
> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
>
> let me know how you want to merge all this.
>
>
>
> > 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/vfio-next-iommu_geometry-v3
> >
> > History:
> > v2 -> v3:
> > - rebase on top of vfio-next (including iommufd prereq)
> > - take into account IOVA range info capability may not be offered by
> >   old kernel and use nr_iovas = -1 to encode that [Alex]
> > - use GList * everywhere instead of arrays (in the range_inverse_array)
> >   with the benefice it sorts ranges retrieved from the kernel which are
> >   not garanteed to be sorted. Rework the tests accordingly [Alex]
> > - Make sure resv_regions GList is build before the probe() [Jean]
> >   per device list is first populated with prop resv regions on
> >   IOMMUDevice creation and then rebuilt on set_iova()
> > - Add a warning if set_iova builds a valid list after probe was
> >   called [Jean]
> > - Build host windows on top of IOVA valid ranges if this info can
> >   be retrieved from the kernel. As many windows are created as
> >   valid ranges
> > 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.
> > - 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 (13):
> >   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
> >   range: Make range_compare() public
> >   util/reserved-region: Add new ReservedRegion helpers
> >   virtio-iommu: Introduce per IOMMUDevice reserved regions
> >   range: Introduce range_inverse_array()
> >   virtio-iommu: Record whether a probe request has been issued
> >   virtio-iommu: Implement set_iova_ranges() callback
> >   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            |  34 +++-
> >  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                 |  23 ++-
> >  hw/vfio/container.c              |  67 ++++++-
> >  hw/virtio/virtio-iommu-pci.c     |   8 +-
> >  hw/virtio/virtio-iommu.c         | 155 +++++++++++++--
> >  system/memory.c                  |  13 ++
> >  tests/unit/test-resv-mem.c       | 318 +++++++++++++++++++++++++++++++
> >  util/range.c                     |  61 +++++-
> >  util/reserved-region.c           |  91 +++++++++
> >  hw/virtio/trace-events           |   1 +
> >  tests/unit/meson.build           |   1 +
> >  util/meson.build                 |   1 +
> >  17 files changed, 791 insertions(+), 46 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
>
>