Bug 2039856

Description of problem:
Boot a RHEL7.9(.z) guest in the RHEL9.0, enabling iommu on the virtio-net device, guest will kerpanic.

Version-Release number of selected component (if applicable):
Host:
5.14.0-39.el9.x86_64
qemu-kvm-6.2.0-2.el9.x86_64

Guest:
3.10.0-1160.53.1.el7.x86_64


How reproducible:
100%

Steps to Reproduce:
1. Prepare a VM image with kernel line has intel_iommu=on 

# cat /proc/cmdline 
BOOT_IMAGE=/vmlinuz-3.10.0-1160.53.1.el7.x86_64 root=/dev/mapper/rhel_vm--74--121-root ro console=tty0 console=ttyS0,115200n8 biosdevname=0 crashkernel=auto spectre_v2=retpoline rd.lvm.lv=rhel_vm-74-121/root rd.lvm.lv=rhel_vm-74-121/swap rhgb quiet LANG=en_US.UTF-8 intel_iommu=on 

2. Boot VM with this image and iommu enabled on the virtio-net device, full cmd refer [1]

-machine q35,kernel-irqchip=split,memory-backend=mem-machine_mem \
-device intel-iommu,intremap=on,device-iotlb=on,caching-mode=on \
-device virtio-net-pci,mac=9a:3a:19:39:ec:75,id=idQMqdcA,netdev=idE9KU8r,bus=pcie-root-port-3,addr=0x0,disable-legacy=on,disable-modern=off,iommu_platform=on,ats=on \
-netdev tap,id=idE9KU8r,vhost=on \

3. Guest fails boot up and kernel crash. The screen image will be in next Comment.


Actual results:
Guest kernel crash.

Expected results:
Guest should not kernel crash. 

Additional info:
1. Full qemu cmd line:
-name 'avocado-vt-vm1'  \
-sandbox on  \
-machine q35,kernel-irqchip=split,memory-backend=mem-machine_mem \
-device pcie-root-port,id=pcie-root-port-0,multifunction=on,bus=pcie.0,addr=0x1,chassis=1 \
-device pcie-pci-bridge,id=pcie-pci-bridge-0,addr=0x0,bus=pcie-root-port-0  \
-nodefaults \
-device intel-iommu,intremap=on,device-iotlb=on,caching-mode=on \
-device VGA,bus=pcie.0,addr=0x2 \
-m 7168 \
-object memory-backend-ram,size=7168M,id=mem-machine_mem  \
-smp 6,maxcpus=6,cores=3,threads=1,dies=1,sockets=2  \
-cpu 'Haswell-noTSX',+kvm_pv_unhalt \
-device pcie-root-port,id=pcie-root-port-1,port=0x1,addr=0x1.0x1,bus=pcie.0,chassis=2 \
-device qemu-xhci,id=usb1,bus=pcie-root-port-1,addr=0x0 \
-device usb-tablet,id=usb-tablet1,bus=usb1.0,port=1 \
-device pcie-root-port,id=pcie-root-port-2,port=0x2,addr=0x1.0x2,bus=pcie.0,chassis=3 \
-device virtio-scsi-pci,id=virtio_scsi_pci0,bus=pcie-root-port-2,addr=0x0 \
-blockdev node-name=file_image1,driver=file,auto-read-only=on,discard=unmap,aio=threads,filename=/home/rhel7.9.qcow2,cache.direct=on,cache.no-flush=off \
-blockdev node-name=drive_image1,driver=qcow2,read-only=off,cache.direct=on,cache.no-flush=off,file=file_image1 \
-device scsi-hd,id=image1,drive=drive_image1,write-cache=on \
-device pcie-root-port,id=pcie-root-port-3,port=0x3,addr=0x1.0x3,bus=pcie.0,chassis=4 \
-device virtio-net-pci,mac=9a:3a:19:39:ec:75,id=idQMqdcA,netdev=idE9KU8r,bus=pcie-root-port-3,addr=0x0,disable-legacy=on,disable-modern=off,iommu_platform=on,ats=on \
-netdev tap,id=idE9KU8r,vhost=on \
-vnc :0  \
-rtc base=utc,clock=host,driftfix=slew  \
-boot menu=off,order=cdn,once=c,strict=off \
-enable-kvm \
-device pcie-root-port,id=pcie_extra_root_port_0,multifunction=on,bus=pcie.0,addr=0x3,chassis=5 \
-monitor stdio \
-qmp tcp:0:5555,server,nowait \


2. This bug was found by Lei yang. He will fill related fields once he come back from PTO.