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documentation.suse.com / SUSE Linux Enterprise Server Documentation / Virtualization Guide / Introduction / Virtualization limits and support
Applies to SUSE Linux Enterprise Server 15 SP3

7 Virtualization limits and support

  
Important
Important

QEMU is only supported when used for virtualization together with the KVM or Xen hypervisors. The TCG accelerator is not supported, even when it is distributed within SUSE products. Users must not rely on QEMU TCG to provide guest isolation, or for any security guarantees. See also https://qemu-project.gitlab.io/qemu/system/security.html.

7.1 Architecture support

  

7.1.1 KVM hardware requirements

  

Currently, SUSE supports KVM full virtualization on AMD64/Intel 64, AArch64, IBM Z, and IBM LinuxONE hosts.

  • On the AMD64/Intel 64 architecture, KVM is designed around hardware virtualization features included in AMD* (AMD-V) and Intel* (VT-x) CPUs. It supports virtualization features of chipsets and PCI devices, such as an I/O Memory Mapping Unit (IOMMU) and Single Root I/O Virtualization (SR-IOV). You can test whether your CPU supports hardware virtualization with the following command: 

    > egrep '(vmx|svm)' /proc/cpuinfo

    If this command returns no output, your processor either does not support hardware virtualization, or this feature has been disabled in the BIOS or firmware.

    The following Web sites identify AMD64/Intel 64 processors that support hardware virtualization: http://ark.intel.com/Products/VirtualizationTechnology (for Intel CPUs), and http://products.amd.com/ (for AMD CPUs).

  • On the Arm architecture, Armv8-A processors include support for virtualization.

  • On the Arm architecture, we only support running QEMU/KVM via the CPU model host (it is named host-passthrough in Virtual Machine Manager or libvirt).

Note
Note: KVM kernel modules not loading

The KVM kernel modules only load if the CPU hardware virtualization features are available.

The general minimum hardware requirements for the VM Host Server are the same as outlined in Section 2.1, “Hardware requirements”. However, additional RAM for each virtualized guest is needed. It should at least be the same amount that is needed for a physical installation. It is also strongly recommended to have at least one processor core or hyper-thread for each running guest.

Note
Note: AArch64

AArch64 is a continuously evolving platform. It does not have a traditional standards and compliance certification program to enable interoperability with operating systems and hypervisors. Ask your vendor for the support statement on SUSE Linux Enterprise Server.

Note
Note: POWER

Running KVM or Xen hypervisors on the POWER platform is not supported.

7.1.2 Xen hardware requirements

  

SUSE supports Xen on AMD64/Intel 64.

7.2 Hypervisor limits

  

New features and virtualization limits for Xen and KVM are outlined in the Release Notes for each Service Pack (SP).

Only packages that are part of the official repositories for SUSE Linux Enterprise Server are supported. Conversely, all optional subpackages and plug-ins (for QEMU, libvirt) provided at packagehub are not supported.

For the maximum total virtual CPUs per host, see recommendations in the Virtualization Best Practices Guide regarding over-commitment of physical CPUs. The total number of virtual CPUs should be proportional to the number of available physical CPUs.

Note
Note: 32-bit hypervisor

With SUSE Linux Enterprise Server 11 SP2, we removed virtualization host facilities from 32-bit editions. 32-bit guests are not affected and are fully supported using the provided 64-bit hypervisor.

7.2.1 KVM limits

  

Supported (and tested) virtualization limits of a SUSE Linux Enterprise Server 15 SP3 host running Linux guests on AMD64/Intel 64. For other operating systems, refer to the specific vendor.

Table 7.1: KVM VM limits
  

Maximum virtual CPUs per VM

288

Maximum memory per VM

6 TiB

Note
Note

KVM host limits are identical to SUSE Linux Enterprise Server (see the corresponding section of release notes), except for:

7.2.2 Xen limits

  
Table 7.2: Xen VM limits
  

Maximum virtual CPUs per VM

32 (general HVM recommendation), 64 (HVM Windows guest), 128 (trusted HVMs), or 512 (PV)

Maximum memory per VM

2 TiB (64-bit guest), 16 GiB (32-bit guest with PAE)

Table 7.3: Xen host limits
  

Maximum total physical CPUs

1024

Maximum total virtual CPUs per host

See recommendations in the Virtualization Best Practices Guide regarding over-commitment of physical CPUs in https://documentation.suse.com/sles-15/html/SLES-all/article-virtualization-best-practices.html#sec-vt-best-perf-cpu-assign. The total virtual CPUs should be proportional to the available physical CPUs

Maximum physical memory

Recommendation is to stay below the 16 TiB address boundary.

Suspend and hibernate modes

Not supported.

7.3 Supported host environments (hypervisors)

  

This section describes the support status of SUSE Linux Enterprise Server 15 SP3 running as a guest operating system on top of various virtualization hosts (hypervisors).

Table 7.4: The following SUSE host environments are supported
  

SUSE Linux Enterprise Server

Hypervisors

SUSE Linux Enterprise Server 11 SP4

Xen and KVM

SUSE Linux Enterprise Server 12 SP1 to SP5

Xen and KVM

SUSE Linux Enterprise Server 15 GA to SP3

Xen and KVM

The following third-party host environments are supported
  

You can also search in the SUSE YES certification database

The level of support is as follows
  

  • Support for SUSE host operating systems is full L3 (both for the guest and host) in accordance with the respective product life cycle.

  • SUSE provides full L3 support for SUSE Linux Enterprise Server guests within third-party host environments.

  • Support for the host and cooperation with SUSE Linux Enterprise Server guests must be provided by the host system's vendor.

7.4 Supported guest operating systems

  

This section lists the support status for various guest operating systems virtualized on top of SUSE Linux Enterprise Server 15 SP3 for KVM and Xen hypervisors.

Important
Important

Microsoft Windows guests can be rebooted by libvirt/virsh only if paravirtualized drivers are installed in the guest. Refer to https://www.suse.com/products/vmdriverpack/ for more details on downloading and installing PV drivers.

The following guest operating systems are fully supported (L3):
  

  • SUSE Linux Enterprise Server 11 SP4

  • SUSE Linux Enterprise Server 12 SP3, 12 SP4, 12 SP5

  • SUSE Linux Enterprise Server 15 GA, 15 SP1, 15 SP2, 15 SP3

  • Windows Server 2008 SP2+, 2008 R2 SP1+, 2012+, 2012 R2+, 2016, 2019, 2022

  • Oracle Linux 6, 7, 8 (KVM hypervisor only)

The following guest operating systems are supported as a technology preview (L2, fixes if reasonable):
  

  • SLED 15 SP3

Red Hat and CentOS guest operating systems are fully supported (L3) if the customer has purchased SUSE Liberty Linux.
  

  • Refer to the SUSE Liberty Linux documentation at https://documentation.suse.com/liberty for the list of available combinations and supported releases. In other cases, they are supported on a limited basis (L2, fixes if reasonable).

Note
Note: RHEL PV drivers

Starting from RHEL 7.2, Red Hat removed Xen PV drivers.

The following guest operating systems are supported on a commercially reasonable basis (L2, fixes if reasonable):
  

  • Windows 8+, 8.1+, 10+

All other guest operating systems
  

  • In other combinations, L2 support is provided but fixes are available only if feasible. SUSE fully supports the host OS (hypervisor). The guest OS issues need to be supported by the respective OS vendor. If an issue fix involves both the host and guest environments, the customer needs to approach both SUSE and the guest VM OS vendor.

  • All guest operating systems are supported both fully virtualized and paravirtualized. The exception is Windows systems, which are only supported fully virtualized (but they can use PV drivers: https://www.suse.com/products/vmdriverpack/), and OES operating systems, which are supported only paravirtualized.

  • All guest operating systems are supported both in 32-bit and 64-bit environments, unless stated otherwise.

7.4.1 Availability of paravirtualized drivers

  

To improve the performance of the guest operating system, paravirtualized drivers are provided when available. Although they are not required, it is strongly recommended to use them.

Starting with SUSE Linux Enterprise Server 12 SP2, we switched to a PVops kernel. We are no longer using a dedicated kernel-xen package:

  • The kernel-default+kernel-xen on dom0 was replaced by the kernel-default package.

  • The kernel-xen package on PV domU was replaced by the kernel-default package.

  • The kernel-default+xen-kmp on HVM domU was replaced by kernel-default.

For SUSE Linux Enterprise Server 12 SP1 and older (down to 10 SP4), the paravirtualized drivers are included in a dedicated kernel-xen package.

The paravirtualized drivers are available as follows:

SUSE Linux Enterprise Server 12 / 12 SP1 / 12 SP2

Included in kernel

SUSE Linux Enterprise Server 11 / 11 SP1 / 11 SP2 / 11 SP3 / 11 SP4

Included in kernel

SUSE Linux Enterprise Server 10 SP4

Included in kernel

Red Hat

Available since Red Hat Enterprise Linux 5.4. Starting from Red Hat Enterprise Linux 7.2, Red Hat removed the PV drivers.

Windows

SUSE has developed virtio-based drivers for Windows, which are available in the Virtual Machine Driver Pack (VMDP). For more information, see https://www.suse.com/products/vmdriverpack/.

7.5 Supported VM migration scenarios

  

SUSE Linux Enterprise Server supports migrating a virtual machine from one physical host to another.

7.5.1 Offline migration scenarios

  

SUSE supports offline migration, powering off a guest VM, then moving it to a host running a different SLE product, from SLE 12 to SLE 15 SPX. The following host operating system combinations are fully supported (L3) for migrating guests from one host to another:

Table 7.5: Offline supported migrating guests from SUSE Linux Enterprise Server 12 SP3
  

Host Source Product Name

To Host Target

SUSE Linux Enterprise Server 12 SP3

SLES 12 SP3

SLES 12 SP4

SLES 12 SP5

SLES 15 GA

Table 7.6: Offline supported migrating guests from SUSE Linux Enterprise Server 12 SP4
  

Host Source Product Name

To Host Target

SUSE Linux Enterprise Server 12 SP4

SLES 12 SP4

SLES 12 SP5

SLES 15 (KVM only)

SLES 15 SP1

Table 7.7: Offline supported migrating guests from SUSE Linux Enterprise Server 12 SP5
  

Host Source Product Name

To Host Target

SUSE Linux Enterprise Server 12 SP5

SLES 12 SP5

SLES 15 SP1

SLES 15 SP2

Table 7.8: Offline supported migrating guests from SUSE Linux Enterprise Server 15 GA
  

Host Source Product Name

To Host Target

SUSE Linux Enterprise Server 15 GA

SLES 15 GA

SLES 15 SP1

SLES 15 SP2

SLES 15 SP3

Table 7.9: Offline supported migrating guests from SUSE Linux Enterprise Server 15 SP1
  

Host Source Product Name

To Host Target

SUSE Linux Enterprise Server 15 SP1

SLES 15 SP1

SLES 15 SP2

SLES 15 SP3

Table 7.10: Offline supported migrating guests from SUSE Linux Enterprise Server 15 SP2
  

Host Source Product Name

To Host Target

SUSE Linux Enterprise Server 15 SP2

SLES 15 SP2

SLES 15 SP3

7.5.2 Live migration scenarios

  

This section lists support status of various live migration scenarios when running virtualized on top of SLES. Also, refer to the supported live migration requirements. The following host operating system combinations are fully supported (L3 in accordance with the respective product life cycle).

Table 7.11: Supported live-migrating guests from SLES 12 SP3
  

Host Source Product Name

To Host Target

SUSE Linux Enterprise Server 12 SP3

SLES 12 SP4

Table 7.12: supported live-migrating guests from SLES 12 SP4
  

Host Source Product Name

To Host Target

SUSE Linux Enterprise Server 12 SP4

SLES 12 SP4

SLES 12 SP5

SLES 15 GA (KVM only)

Table 7.13: Supported live-migrating guests from SLES 12 SP5
  

Host Source Product Name

To Host Target

SUSE Linux Enterprise Server 12 SP5

SLES 12 SP5

SLES 15 SP1

Table 7.14: Supported live-migrating guests from SLES 15
  

Host Source Product Name

To Host Target

SUSE Linux Enterprise Server 15 GA

SLES 15 GA

SLES 15 SP1

Table 7.15: Supported live-migrating guests from SLES 15 SP1
  

Host Source Product Name

To Host Target

SUSE Linux Enterprise Server 15 SP1

SLES 15 SP1

SLES 15 SP2

Table 7.16: Supported live-migrating guests from SLES 15 SP2
  

Host Source Product Name

To Host Target

SUSE Linux Enterprise Server 15 SP2

SLES 15 SP2

SLES 15 SP3

Table 7.17: Supported live-migrating guests from SLES 15 SP3
  

Host Source Product Name

To Host Target

SUSE Linux Enterprise Server 15 SP3

SLES 15 SP3

SLES 15 SP4 (when it is available)
Note
Note: Live migration

  • SUSE always supports live migration of virtual machines between hosts running SLES with successive service pack numbers. For example, from SLES 15 SP2 to 15 SP3.

  • SUSE strives to support live migration of virtual machines from a host running a service pack under LTSS to a host running a newer service pack, within the same major version of SUSE Linux Enterprise Server. For example, virtual machine migration from a SLES 12 SP2 host to a SLES 12 SP5 host. SUSE only performs minimal testing of LTSS-to-newer migration scenarios and recommends thorough on-site testing before attempting to migrate critical virtual machines.

Note
Note: Xen live migration

Live migration between SLE 11 and SLE 12 is not supported because of the different tool stack, see the Release notes for more details.

7.6 Feature support

  

7.6.1 Xen host (Dom0)

  
Table 7.18: Feature support—host (Dom0)
  

Features

Xen

Network and block device hotplugging

Yes

Physical CPU hotplugging

No

Virtual CPU hotplugging

Yes

Virtual CPU pinning

Yes

Virtual CPU capping

Yes

Intel* VT-x2: FlexPriority, FlexMigrate (migration constraints apply to dissimilar CPU architectures)

Yes

Intel* VT-d2 (DMA remapping with interrupt filtering and queued invalidation)

Yes

AMD* IOMMU (I/O page table with guest-to-host physical address translation)

Yes

Note
Note: Adding or removing physical CPUs at runtime is not supported

The addition or removal of physical CPUs at runtime is not supported. However, virtual CPUs can be added or removed for each VM Guest while offline.

7.6.2 Xen paravirtualized guest (DomU)

  
Table 7.19: Feature support—paravirtualized guest
  

Features

Xen

Virtual network and virtual block device hotplugging

Yes

Virtual CPU hotplugging

Yes

Virtual CPU over-commitment

Yes

Dynamic virtual memory resize

Yes

VM save and restore

Yes

VM live migration

Yes (See Section 11.7.1, “Migration requirements”)

Advanced debugging with GDBC

Yes

Dom0 metrics visible to VM

Yes

Memory ballooning

Yes

PCI Pass-Through

Yes (NetWare guests are excluded)

For live migration, both source and target system architectures need to match; that is, the processors (AMD* or Intel*) must be the same. Unless CPU ID masking is used, such as with Intel FlexMigration, the target should feature the same processor revision or a more recent processor revision than the source. If VMs are moved among different systems, the same rules apply for each move. To avoid failing optimized code at runtime or application start-up, source and target CPUs need to expose the same processor extensions. Xen exposes the physical CPU extensions to the VMs transparently. To summarize, guests can be 32-bit or 64-bit, but the VHS must be identical.

Note
Note: Intel flexMigration

For machines that support Intel FlexMigration, CPU-ID masking and faulting allow more flexibility in cross-CPU migration.

7.6.3 Fully virtualized guest

  
Table 7.20: Feature support—fully virtualized guest
  

Features

Xen

KVM

Virtual network and virtual block device hotplugging

Yes

Yes

Virtual CPU hotplugging

No

No

Virtual CPU over-commitment

Yes

Yes

Dynamic virtual memory resize

Yes

Yes

VM save and restore

Yes

Yes

VM Live Migration

Yes (See Section 11.7.1, “Migration requirements”)

Yes

VM snapshot

Yes

Yes

Advanced debugging with GDBC

Yes

Yes

Dom0 metrics visible to VM

Yes

Yes

PCI Pass-Through

Yes

Yes

AMD SEV

No

Yes (See https://documentation.suse.com/sles/15-SP3/html/SLES-amd-sev/article-amd-sev.html)

Note
Note: Windows guest

Hotplugging of virtual network and virtual block devices, and resizing, shrinking, and restoring dynamic virtual memory are supported in Xen and KVM only if PV drivers are being used (VMDP).

For KVM, a detailed description of supported limits, features, recommended settings and scenarios, and other useful information is maintained in kvm-supported.txt. This file is part of the KVM package and can be found in /usr/share/doc/packages/qemu-kvm.

7.7 Nested virtualization

  

Nested virtualization allows you to run a virtual machine inside another VM while still using hardware acceleration from the host. It has very bad performance and adds more complexity while debugging. Nested virtualization is mostly used for testing purposes. In SUSE Linux Enterprise Server, nested virtualization is a Technology Preview. It is only provided for testing purposes and is not supported. Bugs can be reported but they will be treated with low priority. Any attempt to live-migrate or to save or restore VMs in the presence of nested virtualization is also explicitly unsupported.