I'm not sure what's going on here. I mean, in the XML you have model='intel' but in the cmd line there's virtio-iommu. I could not reproduce this problem, can you share full domain XML please? Meanwhile, it's only virtio IOMMU that can have an <address/>, let me post patches for that.

Improvements posted here:

https://listman.redhat.com/archives/libvir-list/2022-July/232686.html

Merged upstream as:

43e9d322be domain_validate: Disallow non-virtio IOMMU with an <address/>
92678703ce docs: Document <address/> for IOMMU device
4a9c86ee2f qemu_domain_address: Drop needless virDomainIOMMUModel typecast

v8.5.0-50-g43e9d322be

(In reply to Michal Privoznik from comment #1)
> I'm not sure what's going on here. I mean, in the XML you have model='intel'
> but in the cmd line there's virtio-iommu. I could not reproduce this
> problem, can you share full domain XML please? Meanwhile, it's only virtio
> IOMMU that can have an <address/>, let me post patches for that.

Sorry, I must have copy-paste error there. I have updated the description in comment 0.
# virsh dumpxml rhel 
<disk type='file' device='disk'>
      <driver name='qemu' type='qcow2' iommu='on' ats='on'/>
      <source file='/var/lib/libvirt/images/RHEL-9.1.0-20220518.1-x86_64-ovmf.qcow2' index='1'/>
      <backingStore/>
      <target dev='vda' bus='virtio'/>
      <boot order='1'/>
      <alias name='virtio-disk0'/>
      <address type='pci' domain='0x0000' bus='0x05' slot='0x00' function='0x0'/>
    </disk>
<interface type='network'>
      <mac address='52:54:00:2b:f0:91'/>
      <source network='default' portid='28469d51-52ab-40f6-b40d-f1623a3d9df6' bridge='virbr0'/>
      <target dev='vnet12'/>
      <model type='virtio'/>
      <driver iommu='on' ats='on'/>
      <alias name='net0'/>
      <address type='pci' domain='0x0000' bus='0x03' slot='0x00' function='0x0'/>
    </interface>
......
    <iommu model='virtio'>
      <driver intremap='on' caching_mode='on' eim='on' iotlb='on'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
    </iommu>

Related qemu cmd line:
-device {"driver":"virtio-iommu","bus":"pcie.0","addr":"0x4"}
-blockdev {"node-name":"libvirt-1-format","read-only":false,"driver":"qcow2","file":"libvirt-1-storage","backing":null} 
-device {"driver":"virtio-blk-pci","iommu_platform":true,"ats":true,"bus":"pci.5","addr":"0x0","drive":"libvirt-1-format","id":"virtio-disk0","bootindex":1}
-netdev tap,fd=23,vhost=on,vhostfd=25,id=hostnet0
-device {"driver":"virtio-net-pci","iommu_platform":true,"ats":true,"netdev":"hostnet0","id":"net0","mac":"52:54:00:2b:f0:91","bus":"pci.3","addr":"0x0"}

There is another qemu bug about the ats support(Bug 2101632) since virtio iommu do not support ats and device-iotlb.

(In reply to Michal Privoznik from comment #1)
> problem, can you share full domain XML please? Meanwhile, it's only virtio
> IOMMU that can have an <address/>, let me post patches for that.

Yes, from the test results, only virtio iommu will have an <address/>, intel iommu does not have an <address/>.

Patches posted here:

https://listman.redhat.com/archives/libvir-list/2022-July/232726.html

https://listman.redhat.com/archives/libvir-list/2022-August/233572.html

commit c5bc752666ab0fc9799e7b9139e1035fe279e97f
Author:     Michal Prívozník <mprivozn>
AuthorDate: Fri Jul 8 11:33:02 2022 +0200
Commit:     Michal Prívozník <mprivozn>
CommitDate: Mon Aug 8 16:59:55 2022 +0200

    conf: Check IOMMU for unsupported attributes
    
    Currently, it's possible to pass various attributes to an IOMMU's
    <driver/> element hoping that we enable them in underlying
    hypervisor. However, depending on the IOMMU model, some of these
    attributes can't be enabled and are simply ignored. This is
    suboptimal and we should reject such configuration in the
    validate phase.
    
    Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=2101633
    Signed-off-by: Michal Privoznik <mprivozn>
    Reviewed-by: Ján Tomko <jtomko>

v8.6.0-64-gc5bc752666

Test on libvirt-8.7.0-1.el9.x86_64, either of the attributes: 'intremap', 'caching_mode', 'eim', 'iotlb' or 'aw_bits' can not be validated, which is expected.

# virsh edit rhel
error: XML error: iommu model 'virtio' doesn't support additional attributes
Failed. Try again? [y,n,i,f,?]:

To define a vm with the unsupported attributes:
# virsh define rhel.xml
error: Failed to define domain from rhel.xml
error: XML error: iommu model 'virtio' doesn't support additional attributes

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (libvirt bug fix and enhancement update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2023:2171