Re: [PATCH 00/13] VIRTIO-IOMMU/VFIO: Don't assume 64b IOVA space

[Eric Auger]

Hi Yanghang,

On 9/5/23 10:22, YangHang Liu wrote:
> I have runned the following two tests, but both tests failed:
> [1] start a VM with virtio-iommu + 2 ice PFs only via qemu-kvm 8.1.5
> Test result : the qemu-kvm keeps throwing the error:  VFIO_MAP_DMA
> failed: File exists. vfio_dma_map(0x56443d20fbe0, 0xffffe000, 0x1000,
> 0x7fb545709000) = -17 (File exists)
> [2] start a VM with virtio-iommu + 2 ice PFs via libvirt-9.5 + qemu-kvm 8.1.5
> Test result: the qemu-kvm core dump with
> ERROR:../qom/object.c:1198:object_unref: assertion failed: (obj->ref >
> 0). Bail out! ERROR:../qom/object.c:1198:object_unref: assertion
> failed: (obj->ref > 0)
>
> After removing the 2 PF from the VM, both tests passed.
> Tested-by: Yanghang Liu <yanghliu@redhat.com>

thank you for testing. If my understanding is correct you still
encountered some issues with/after the series. If this is correct you
shall not offer your Tested-by which means you tested the series and it
works fine for you/fixes your issue.

Coming back to the above mentionned issues:

1) the File Exists issue is known and is linked to the replay. This will
be handled separately, ie.I need to resume working on it as my first
approach was flawed: See
https://lore.kernel.org/all/20221207133646.635760-1-eric.auger@redhat.com/
This is unrelated to this series. Note this shouldn't prevent your
passthroughed device from working. Those should be just spurious
warnings that need to be removed.

2) the object_unref assertion most probaly is linked to that series and
I will to investigate asap.

Thank you again!

Eric
>
> Best Regards,
> YangHang Liu
>
>
> On Mon, Sep 4, 2023 at 4:08 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_v1
>>
>> 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
>>   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
>>   virtio-iommu: Resize memory region according to the max iova info
>>   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             |   9 ++
>>  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         |  85 +++++++++++--
>>  softmmu/memory.c                 |  15 +++
>>  tests/unit/test-resv-mem.c       | 198 +++++++++++++++++++++++++++++++
>>  util/range.c                     |  41 ++++++-
>>  util/reserved-region.c           |  94 +++++++++++++++
>>  hw/virtio/trace-events           |   1 +
>>  tests/unit/meson.build           |   1 +
>>  util/meson.build                 |   1 +
>>  16 files changed, 562 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
>>
>>