Score:1

Server

Ubuntu 22 No ACPI DMAR table found, IOMMU either disabled in BIOS or not supported by this hardware platform on nested VM

shorif2000

1/4/24, 12:10 AM

I am using ubuntu 22.04 LTS minimal server. My host server is set up with kvm and is functioning well. All tests pass when running virt-host-validate.

When I create. virtual machine i want this to support kvm also and I am trying to make all the checks to pass when running virt-host-validate on the Virtual Machine, which is laso ubuntu 22.04 LTS

I have updated the following lines on grub on VM

GRUB_CMDLINE_LINUX_DEFAULT="intel_iommu=on"
GRUB_CMDLINE_LINUX="cgroup_memory=1 cgroup_enable=memory swapaccount=1 systemd.unified_cgroup_hierarchy=0 intel_iommu=on"

run sudo update-grub and rebooted VM. I still get warning

  QEMU: Checking for device assignment IOMMU support                         : WARN (No ACPI DMAR table found, IOMMU either disabled in BIOS or not supported by this hardware platform)

I need this to pass to able to use KubeVirt properly.

https://pastebin.com/gUtdswz0

On my host/hardware

$ sudo dmesg | grep -e DMAR -e IOMMU
[    0.025208] ACPI: DMAR 0x000000007B7E6000 000364 (v01 INTEL  INTEL ID 00000001 ?    00000001)
[    0.025303] ACPI: Reserving DMAR table memory at [mem 0x7b7e6000-0x7b7e6363]
[    1.958464] DMAR: IOMMU enabled
[    3.615052] DMAR: Host address width 46
[    3.615056] DMAR: DRHD base: 0x000000fbffc000 flags: 0x0
[    3.615070] DMAR: dmar0: reg_base_addr fbffc000 ver 1:0 cap 8d2078c106f0466 ecap f020de
[    3.615079] DMAR: DRHD base: 0x000000c7ffc000 flags: 0x1
[    3.615093] DMAR: dmar1: reg_base_addr c7ffc000 ver 1:0 cap 8d2078c106f0466 ecap f020de
[    3.615100] DMAR: RMRR base: 0x00000079170000 end: 0x00000079172fff
[    3.615107] DMAR: RMRR base: 0x000000791f4000 end: 0x000000791f7fff
[    3.615113] DMAR: RMRR base: 0x000000791de000 end: 0x000000791f3fff
[    3.615118] DMAR: RMRR base: 0x000000791cb000 end: 0x000000791dbfff
[    3.615123] DMAR: RMRR base: 0x000000791dc000 end: 0x000000791ddfff
[    3.615128] DMAR: RMRR base: 0x0000005a62f000 end: 0x0000005a69efff
[    3.615136] DMAR: ATSR flags: 0x0
[    3.615141] DMAR: ATSR flags: 0x0
[    3.615148] DMAR-IR: IOAPIC id 10 under DRHD base  0xfbffc000 IOMMU 0
[    3.615155] DMAR-IR: IOAPIC id 8 under DRHD base  0xc7ffc000 IOMMU 1
[    3.615160] DMAR-IR: IOAPIC id 9 under DRHD base  0xc7ffc000 IOMMU 1
[    3.615166] DMAR-IR: HPET id 0 under DRHD base 0xc7ffc000
[    3.615171] DMAR-IR: Queued invalidation will be enabled to support x2apic and Intr-remapping.
[    3.616770] DMAR-IR: Enabled IRQ remapping in x2apic mode
[    4.937442] DMAR: No SATC found
[    4.937451] DMAR: dmar0: Using Queued invalidation
[    4.937474] DMAR: dmar1: Using Queued invalidation
[    4.968865] DMAR: Intel(R) Virtualization Technology for Directed I/O

On my first VM

$ sudo dmesg | grep -e DMAR -e IOMMU
[    1.982119] DMAR: IOMMU enabled

1046

1 + 5

ubuntu

qemu

kvm-virtualization

Simon Richter

1/4/24, 1:11 AM

The error message suggests checking the BIOS settings -- VT-d must be enabled.

shorif2000

1/4/24, 5:00 PM

the host hardware is enabled and working

Mircea Vutcovici

1/11/24, 1:42 PM

I would like to understand better why do you need vIOMMU? Are you planning to expose a PCI device to an inner VM? What is the use case?

Mircea Vutcovici

1/11/24, 1:55 PM

Could you please refine the question to include the following? 1. Information of the hardware (server manufacturer, and model, SR-IOV NIC manufacturer and model) 2. What did you configure for IOMMU: BIOS/UEFI settings, kernel cmdline, /etc/modprobe.d/vfio.conf ... 3. What is your use case and what is the big picture.

Mircea Vutcovici

1/11/24, 1:56 PM

Please add a link to the output of `virsh dumpxml <VM_name>`

Score:2

Server

Mircea Vutcovici

1/4/24, 12:37 AM

If you are not planning to use PCI passtrough or SR-IOV in the nested VM, then you can safely ignore those warnings.

Those technologies are used to expose a physical device, like a video card or a network card PCI virtual function, to a VM.

For host VM (the outer VM), make sure you enable vIOMMU with -device intel-iommu,intremap=on. See also: https://wiki.qemu.org/Features/VT-d

For virtlib, see: https://libvirt.org/formatdomain.html#iommu-devices You will need to have something like:

<features>
    <ioapic driver='qemu'/>
</features>
<!-- ... ->
<devices>
    <iommu model='intel'>
        <driver intremap='on' caching_mode='on'/>
    </iommu>
</devices>

To edit the config:

# List all instances (including stopped ones):
virsh list --all
# Backup current config
virsh dumpxml <VM_Name>  > virsh_dumpxml_VMname-$(date +%F_%H%M%S).txt
# Shutdown, gracefully, the instance:
virsh shutdown <VM_Name>
# Edit the config:
virsh edit <VM_Name>
# Start the VM:
virsh start <VM_Name>

+ 6

shorif2000

1/4/24, 4:51 PM

`-device intel-iommu,intremap=on` does this go on grub?

Mircea Vutcovici

1/4/24, 6:51 PM

No, it's a `qemu` parameter. Just follow the link to qemu documentation to see the examples.

shorif2000

1/4/24, 10:56 PM

I used virt-manager to create the VM. how would I add this option through virt-manager

shorif2000

1/4/24, 11:02 PM

I added some more output on my question

Mircea Vutcovici

1/4/24, 11:35 PM

Updated answer. See: https://libvirt.org/formatdomain.html#iommu-devices and https://bugzilla.redhat.com/show_bug.cgi?id=1427005

Mircea Vutcovici

1/11/24, 2:06 PM

`virt-manager` and `virsh` are frontends for `vitlib`. With `virsh` it is much easier to do some low level stuff. Both of them are working with the same backend - `libvirtd`.

Elon Musk

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EN: Ubuntu 22 No ACPI DMAR table found, IOMMU either disabled in BIOS or not supported by this hardware platform on nested VM

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