Re: [PATCH v4 0/2] vhost: register and change IOMMU flag depending on ATS state

[Michael S. Tsirkin]

On Thu, May 25, 2023 at 03:57:40PM +0300, Viktor Prutyanov wrote:
> When IOMMU and vhost are enabled together, QEMU tracks IOTLB or
> Device-TLB unmap events depending on whether Device-TLB is enabled. But
> even if Device-TLB and PCI ATS is enabled, the guest can reject to use
> it. For example, this situation appears when Windows Server 2022 is
> running with intel-iommu with device-iotlb=on and virtio-net-pci with
> vhost=on. The guest implies that no address translation info cached in
> device IOTLB and doesn't send device IOTLB invalidation commands. So,
> it leads to irrelevant address translations in vhost-net in the host
> kernel. Therefore network frames from the guest in host tap interface
> contains wrong payload data.
> 
> This series adds checking of ATS state for proper unmap flag register
> (IOMMU_NOTIFIER_UNMAP or IOMMU_NOTIFIER_DEVIOTLB_UNMAP).
> 
> Tested on Windows Server 2022, Windows 11 and Fedora guests with
>  -device virtio-net-pci,bus=pci.3,netdev=nd0,iommu_platform=on,ats=on
>  -netdev tap,id=nd0,ifname=tap1,script=no,downscript=no,vhost=on
>  -device intel-iommu,intremap=on,eim=on,device-iotlb=on/off
> Tested on Fedora guest with
>  -device virtio-iommu

Fails build on windows hosts:

https://gitlab.com/mstredhat/qemu/-/pipelines/909063579/failures

C:\GitLab-Runner\builds\mstredhat\qemu\output/../hw/net/virtio-net.c:3954: 
undefined reference to `vhost_toggle_device_iotlb'




> Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=2001312
> 
> v4: call vhost_toggle_device_iotlb regardless of vhost backend,
>     move vhost_started check to generic part
> v3: call virtio_pci_ats_ctrl_trigger directly, remove
>     IOMMU_NOTIFIER_UNMAP fallbacks
> v2: remove memory_region_iommu_notify_flags_changed, move trigger to
>     VirtioDeviceClass, use vhost_ops, use device_iotlb name
> 
> Viktor Prutyanov (2):
>   vhost: register and change IOMMU flag depending on Device-TLB state
>   virtio-net: pass Device-TLB enable/disable events to vhost
> 
>  hw/net/virtio-net.c       |  1 +
>  hw/virtio/vhost.c         | 38 ++++++++++++++++++++++++++------------
>  include/hw/virtio/vhost.h |  1 +
>  3 files changed, 28 insertions(+), 12 deletions(-)
> 
> -- 
> 2.21.0