Fix included in qemu-kvm-rhev-2.9.0-16.el7_4.1

Reproduce bug with the following steps:

host kernel: 3.10.0-693.el7.x86_64
guest kernel: 3.10.0-693.el7.x86_64
qemu-kvm-rhev-2.9.0-16.el7
seabios-1.10.2-3.el7.x86_64


1. In host, add "iommu=pt intel_iommu=on" to kernel line
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 \
  -cpu host \
  -enable-kvm \
  -m 2G \
  -smp 4 \
  -nodefconfig \
  -rtc base=localtime,driftfix=slew \
  -device virtio-scsi-pci,disable-legacy=on,disable-modern=off,iommu_platform=on,id=scsi0,bus=pcie.0 \
  -drive file=rhel74-64-virtio-scsi.raw,if=none,serial=virtioblk1,format=raw,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 \
  


Actual results:
After step 3: Boot failed: could not read the boot disk

Expected results:
guest works well


Retest on the below version, guest boot up and works well.
host kernel: 3.10.0-693.el7.x86_64
guest kernel: 3.10.0-693.el7.x86_64
qemu-kvm-rhev-2.9.0-16.el7_4.1
seabios: https://bugzilla.redhat.com/attachment.cgi?id=1293726 (bios that supports IOMMU_PLATFORM), add "-bios bios.bin \" to cmd

Additional info:
if not add "-bios bios.bin" to command line when tested qemu-kvm-rhev-2.9.0-16.el7_4.1, the guest also can not boot up.


Hi Jason,

If the steps are enough to verify this bug, if not correct me please. Many thanks.

I think it's sufficient. But for safety, we'd better wait for seabios patch to be merged to verify the bug.

Thanks a lot.

Missing "-device intel-iommu,device-iotlb=on,intremap" in cml in Comment 4, so update cml (According to https://bugzilla.redhat.com/show_bug.cgi?id=1283251#c48), and update steps as below.

1. In host, add "iommu=pt intel_iommu=on" to kernel line
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=rhel74-64-virtio-scsi.raw,if=none,serial=virtioblk1,format=raw,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 \
  -bios bios.bin \
4. verify IOMMU enabled, in the guest
   # journalctl -k | grep -i "IOMMU enabled"
   # journalctl -k | grep -i "DMAR: Intel(R) Virtualization Technology for Directed I/O"

Actual results:
After step 3: Boot failed: could not read the boot disk

Expected results:
After step 3: guest works well
After step 4: value likes below.
             # journalctl -k | grep -i "IOMMU enabled"
             Jul 18 13:19:49 localhost kernel: DMAR: IOMMU enabled
             # journalctl -k | grep -i "DMAR: Intel(R) Virtualization Technology for Directed I/O"
            Jul 18 13:19:49 localhost kernel: DMAR: Intel(R) Virtualization Technology for Directed I/O

According to the steps in Comment 6, retested on below version, not hit this issue. So verify the bug.

host kernel: 3.10.0-693.el7.x86_64
guest kernel: 3.10.0-693.el7.x86_64
qemu-kvm-rhev-2.9.0-16.el7_4.1
seabios-1.10.2-4.el7_4.x86_64


After step 3: guest works well
After step 4: value likes below.
# journalctl -k | grep -i "IOMMU enabled"
Jul 27 05:34:31 localhost kernel: DMAR: IOMMU enabled
# journalctl -k | grep -i "DMAR: Intel(R) Virtualization Technology for Directed I/O"
Jul 27 05:34:31 localhost kernel: DMAR: Intel(R) Virtualization Technology for Directed I/O

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, 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/RHSA-2017:2390