Bug 1686278

When verify bug [1], hit this issue. 

[1] Bug 1597482 - qemu crashed when disk enable the IOMMU


Details as below:

Host:
kernel-3.10.0-1010.el7.x86_64
qemu-kvm-rhev-2.12.0-24.el7

Guest:
kernel-3.10.0-1010.el7.x86_64

1. In host, add "iommu=pt intel_iommu=on" to kernel line, then reboot host

2. Add "intel_iommu=on" to kernel line of q35 guest

3. boot virtio-scsi with iommu_platform=on 
/usr/libexec/qemu-kvm \ 
-M q35,kernel-irqchip=split \
-cpu host \ 
-enable-kvm \ 
-m 2G \ 
-smp 4 \ 
-nodefconfig \ 
-rtc base=localtime,driftfix=slew \ 
-device intel-iommu,device-iotlb=on,intremap \ 
-device virtio-scsi-pci,disable-legacy=on,disable-modern=off,iommu_platform=on,ats=on,id=scsi0,bus=pcie.0 \ 
-drive file=rhel76-64-virtio-scsi.qcow2,if=none,format=qcow2,cache=none,werror=stop,rerror=stop,id=drive-virtio-disk0,aio=native \ 
-device scsi-hd,bus=scsi0.0,drive=drive-virtio-disk0,id=virtio-disk0 \ 
-device piix3-usb-uhci,id=usb \ 
-device usb-tablet,id=tablet0 \ 
-vnc :0 \ 
-k en-us \ 
-vga std \ 
-qmp tcp:0:4444,server,nowait \ 
-boot menu=on \ 
-monitor stdio \ 
-device virtio-net-pci,mac=fa:f7:f8:5f:fa:5b,id=idn0VnaA,vectors=4,netdev=id8xJhp7,bus=pcie.0,addr=06 \ 
-netdev tap,id=id8xJhp7,vhost=on \

4. verify IOMMU enabled, in the guest 
# journalctl -k | grep -i "IOMMU enabled" 
Feb 28 11:13:59 localhost kernel: DMAR: IOMMU enabled
# journalctl -k | grep -i "DMAR: Intel(R) Virtualization Technology for Directed I/O"
Feb 28 11:13:59 localhost kernel: DMAR: Intel(R) Virtualization Technology for Directed I/O


Hit below issue during booting guest.

# sh bug_iommu.sh 
QEMU 2.12.0 monitor - type 'help' for more information
(qemu) qemu-kvm: vtd_iommu_translate: detected translation failure (dev=00:02:00, iova=0x0)
qemu-kvm: New fault is not recorded due to compression of faults
qemu-kvm: virtio: zero sized buffers are not allowed

(qemu) system_reset 
(qemu) qemu-kvm: Guest says index 29281 is available
qemu-kvm: virtio: zero sized buffers are not allowed

(qemu) system_powerdown

Yep, I agree.

*** Bug 1722789 has been marked as a duplicate of this bug. ***

QEMU has been recently split into sub-components and as a one-time operation to avoid breakage of tools, we are setting the QEMU sub-component of this BZ to "General". Please review and change the sub-component if necessary the next time you review this BZ. Thanks

Move to the general virt-maint backlog

After evaluating this issue, there are no plans to address it further or fix it in an upcoming release.  Therefore, it is being closed.  If plans change such that this issue will be fixed in an upcoming release, then the bug can be reopened.

QE agree to close due to not hit this issue in current release.
qemu-kvm-common-5.2.0-14.module+el8.4.0+10425+ad586fa5.x86_64