QEMU v2.12 released

QEMU v2.12 is out. Here are the highlights from a KVM on Z perspective:

• Added support for an interactive bootloader. As always, we strongly recommend to use the existing support in libvirt.
  To enable/disable, add the following element to your guest definition:
  
     <os>
       <bootmenu enable=’yes|no’ timeout=’n’/>
       ...
     </os>
  
  The timeout parameter specifies a timeout in milliseconds after which the default entry is chosen.
  Alternatively, set attribute loadparm to PROMPT to enable the boot menu without timeout in the respective disk's element:
  
     <disk ...>
       <boot order=’1’ loadparm=’PROMPT’/>
       ...
     </disk>
  
  Example:
  To enable the boot menu for 32 seconds for a guest using a libvirt
  domain XML format follows:
  
     <domain type=’kvm’>
       <os>
         <bootmenu enable=’yes’ timeout=’32000’/>
         ...
       </os>
• Exposure of guest crash information: When a guest is started using libvirt and crashes due to disabled wait, wrong interrupts or a program check loop, libvirt will print the information to the guest’s log, typically located at /var/log/libvirt/qemu.
  E.g. a crash due to a disabled wait results in an entry as follows:
  
     s390: psw-mask=’0xXXXXXXXXXXXXXXXX’, psw-addr=’0xXXXXXXXXXX
           XXXXXX’,crash reason: disabled wait
  
  Requires  libvirt v4.2.
• Added support for guests with more than 8TB of memory.

RHEL 7.5 with support for KVM on Z available

Red Hat Enterprise Linux 7.5 is out. From the release notes, available here:

Availability across multiple architectures
To further support customer choice in computing architecture, Red Hat Enterprise Linux 7.5 is simultaneously available across all supported architectures, including x86, IBM Power, IBM z Systems, and 64-bit Arm.

Support for IBM Z is available through the kernel-alt package, as indicated earlier here, which provides Linux kernel 4.14. QEMU ships v2.10 via package qemu-kvm-ma, and libvirt is updated to v3.9.0 for all platforms.
Thereby, all IBM z14 features as previously listed here are available.
Check these instructions on how to get started. 

SLES 12 SP3 Updates

SLES 12 SP3, released late last year, received a couple of mostly performance and security-related updates in support of IBM z14 and LinuxONE through the maintenance web updates.
In particular:

• Instruction Execution Protection
• SIMD Extensions
• STHYI Support
• Transparent activation of new hardware features: This will enable a set of performance-oriented hardware facilities of z14 that do not require hypervisor changes.
  This includes the following facilities:
• miscellaneous-instruction-extensions facility 2
• entropy-encoding compression facility
• order-preserving-compression facility

RHEL 7.5 Beta supports KVM on Z

The Red Hat Enterprise Linux 7.5 Beta ships with support for KVM on Z through the kernel-alt packages. This will essentially ship Linux kernel 4.14.
Here is the respective section from the release notes:

KVM virtualization is now supported on IBM z Systems. However, this feature is only available in the newly introduced user space based on kernel version 4.14, provided by the kernel-alt packages.

See here for further details.

QEMU v2.11 released

QEMU v2.11 is out. Here are the highlights from a KVM on Z perspective:

• TOD-Clock Epoch Extension Support: Extends the TOD clock beyond the year 2042.
• Setting sysctl vm.allocate_pgste is now superfluous.
• Netboot: The network boot firmware sets the client architecture option (93) in the DHCP request to 0x1f ("s390 Basic"). This allows a DHCP server to deliver the correct boot image for IBM Z guests. This is useful in situations where a single DHCP server has to provide network boot images for multiple architectures, e.g. for the purpose of installing operating systems.
• Added support for virtio-input-ccw and virtio-gpu-ccw. These newly supported devices lay the foundation for applications that require graphical interfaces, which thereby become usable from remote via VNC or SPICE.
  Here is a sample XML snippet for a guest definition:
  
      <input type='keyboard' bus='virtio'/>
      <graphics type='vnc' port='-1' autoport='yes' listen='0.0.0.0'>
        <listen type='address' address='0.0.0.0'/>
      </graphics>
      <video>
        <model type='virtio' heads='1' primary='yes'/>
      </video>

QEMU v2.10 released

QEMU v2.10 is out. See here for a detailed list of all changes related to IBM Z. Here are some of the highlights from a KVM on z perspective:

• z14 CPU model
  Provides base support for all of the features introduced with the z14's new processor generation.
  See this previous blog post for details.
• Emulated 3270 Device
  This implementation has been tested with x3270 only. Your mileage with other clients might vary. For practical matters, the sclp console remains to be the recommended terminal type for KVM guests on Z.
  As this feature is still marked as experimental in QEMU, there is currently no libvirt support available. Therefore to configure a 3270 device on a guest (accessible on all IP addresses of the host at port 23), we must use libvirt’s ability to pass-through arbitrary QEMU command line arguments via domain XML (see here for furher details):

  <domain type='kvm' xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'>   …   <qemu:commandline>     <qemu:arg value="-chardev"/>     <qemu:arg value="socket,id=charconsole1,host=0.0.0.0,port=23,\                        nowait,server,tn3270"/>     <qemu:arg value="-device"/>     <qemu:arg value="x-terminal3270,chardev=charconsole1,\                       devno=fe.0.000a,id=terminal1"/>   </qemu:commandline>   … </domain>

  See here for further hints on how to use.
• Bootparameter Support
  Until now, when a guest had multiple kernels to boot with, one had to change the default kernel in /etc/zipl.conf and re-run zipl to boot with a different kernel next time.
  With this feature, we now support option -L in the chreipl command from the s390-tools package, which allows to switch to a different boot option dynamically, e.g. using

$ chreipl ccw -d 0.0.1234 -L 2

However, if somebody has set a new default kernel that does not boot, this will not help, since the guest will not start anymore in the first place.
However, with the newly introduced attribute loadparm, one can switch to a different (working) kernel within the host in a guest's XML:

<disk> ... <boot order='1' loadparm='2'> </disk>

Notes:
• chreipl changes will no longer be effective after the respective guest has been powered off.
• The loadparm attribute became available with libvirt v3.5 or higher. 

KVM on z14 features

While the latest addition to the IBM Z family has been announced, here is a list of features in support of specific features of the new hardware generation in past releases of the Linux kernel, QEMU and libvirt, all activated by default in the z14 CPU model:

• Instruction Execution Protection
  This feature provides KVM hypervisor support for the Instruction Execution Protection (IEP) facility in the z14. The IEP prevents code execution from memory regions marked as non-executable, improving the security model.
  Other than activating/deactivating this feature in the applicable the CPU models in QEMU (which holds true for most hardware-related features on IBM Z in general), there are no switches associated with this feature.
  Requires Linux kernel 4.11 in the KVM host and guests, as well as QEMU v2.10 (host only).
  In the z14 CPU model, the respective feature is:
    iep       Instruction-execution-protection facility
• SIMD Extensions
  Following up to the SIMD instructions as introduced with the previous z13 model, the new z14 provides further vector instructions, which can again be used in KVM guests.
  These new vector instructions can be used to improve decimal calculations as well as for implementing high performance variants of certain cryptographic operations.
  Requires Linux kernel 4.11 as well as QEMU v2.10 in the KVM host, and binaries or a respective Java Runtime Environment in guests using the new vector instructions.
  In the z14 CPU model, the respective feature is:
    vxpd      Vector packed decimal facility
    vxeh      Vector enhancements facility
• Keyless Guest Support
  This feature supports the so-called Keyless Subset (KSS) facility, a new feature of the z14 hardware. With the KSS facility enabled, a host is not required to perform the (costly) storage key initialization and management for KVM guests, unless a guest issues a storage key instruction.
  Requires Linux kernel 4.12 in the KVM host. As for the guests, note that starting with SLES12SP1, RHEL7.2 and Ubuntu 16.04, Linux on IBM Z does not issue any storage key operations anymore.
  This feature does not have a separate entry in the z14 CPU model.
  
• CPUMF Basic Sample Configuration Level Indication
  Basic mode samples as defined in "The Load-Program-Parameter and the CPU-Measurement Facilities" (SA23-2260) do not provide an indication whether the sample was taken in a KVM host or guest. Beginning with z14, the hardware provides an indication of the configuration level (level of SIE, e.g. LPAR or KVM). This item exploits this information to make the perf guest/host decision reliable.
  Requires Linux kernel 4.12 in the KVM host.
  There is no separate entry in the z14 CPU model, since this feature applies to the host only.
• Semaphore assist
  Improves performance of semaphore locks.
  Requires Linux kernel 4.7 and QEMU v2.10 in the KVM host. Exploitation in Linux kernels in guests is still in progress here, scheduled for 4.14.
  In the z14 CPU model, the respective feature is:
    sema      Semaphore-assist facility
• Guarded storage
  This feature is specifically aimed at Java Virtual Machines running in KVM guests to run with fewer and shorter pauses for garbage collection.
  Requires Linux kernel 4.12 and QEMU 2.10 in the KVM host, and a Java Runtime Environment with respective support in the guests.
  In the z14 CPU model, the respective feature is:
    gs        Guarded-storage facility
• MSA Updates
  z14 introduces 3 new Message Security Assists (MSA) for the following functionalities:
      MSA6: SHA3 hashing
      MSA7: A True Random  Number Generator (TRNG)
      MSA8: The CIPHER MESSAGE WITH AUTHENTICATION instruction,
                  which provides support for the Galois-counter-mode (GCM)
  MSA6 and MSA 7 require Linux kernel 4.7, while MSA8 requires Linux kernel 4.12. All require QEMU v2.10 in the KVM host. These features can be exploited in KVM guests' kernels and userspace applications independently (i.e. a KVM guest's userspace applications can take advantage of these features irrespective of the guest's kernel version).
  In the z14 CPU model, the respective features are:
    msa6      Message-security-assist-extension 6 facility
    msa7      Message-security-assist-extension 7 facility
    msa8      Message-security-assist-extension 8 facility
• Compression enhancements
  New instructions improve compression capabilities and performance.
  Requires Linux kernel 4.7 in the KVM host.
  In the z14 CPU model, the respective features are:
    opc       Order Preserving Compression facility
    eec       Entropy encoding compression facility
• Miscellaneous instructions
  Details on these instructions are to be published in the forthcoming z14 Principles of Operation (PoP).
  Requires Linux kernel 4.7 and QEMU 2.10 in the KVM host, and binaries that were compiled for the z14 instruction set using binutils v2.28 and gcc v7.1 in the guests.
  In the z14 CPU model, the respective feature is:
    minste2   Miscellaneous-instruction-extensions facility 2

Note: All versions specified are minimum versions.

Further features will be announced in future blog posts as usual as they find their way into the respective Open Source projects.
Also, don't forget to check this blog entry with further details on z14 in general and Linux on z in particular.

z14 announced

Today, IBM announced the new IBM Z model named z14. See here for the full press release.

We will look at features in support of the new IBM Z model in a separate blog entry soon.

Migrating from KVM for IBM z to Ubuntu

In case you are contemplating a migration from KVM for IBM z to Ubuntu 16.04 or later, you might find the instructions published on the Ubuntu Wiki here helpful.

Furthermore, Canonical published a nice article here that provides an overview of the many options how to deploy Ubuntu on IBM z Systems, including KVM.

libvirt v.3.5.0 released

libvirt v3.5.0 is now available for download at the libvirt project website.
A new z Systems-specific feature is the introduction of parameter loadparm for boot devices.
The loadparm parameter can be used to select a specific boot configuration from the zipl menu when IPL’ing/booting from a boot device, similar to what the chreipl command does in Linux on z.
Being able to select a configuration from multiple boot configurations provides more flexibility and allows to recover from error situations by booting a "last known good configuration".
To use, specify the loadparm attribute for a boot device in a guest's XML as follows:

   <disk>
      <boot order='1' loadparm='3'/>
      [...]
   </disk>

Note that this feature requires the forthcoming QEMU 2.10 release.

QEMU v2.9 released

QEMU v2.9 is out. Here are the highlights from a KVM on z perspective:

• Added support for virtio-crypto, providing a virtual crypto device as a front-end to the host's crypto capabilities on z Systems.
• Added multiqueue support for virtio-ccw devices, improving throughput in presence of multiple processors.
• Provided network boot enablement. See here for further details.

Linux kernel 4.11 released

Linux kernel 4.11 (available here) has been released, improving Kernel Samepage Merging (KSM) support for KVM on z:

KSM is an existing feature of the Linux kernel that allows the kernel to merge pages with identical content, indicated as MADV_MERGEABLE via madvise(), across different processes to save memory.
This z Systems specific extension improves the performance of userspace applications (e.g. QEMU) in case large amounts of empty/zeroed pages are merged.
This feature is disabled by default, enable as follows:

   $ echo 1 > /sys/kernel/mm/ksm/use_zero_pages

Knowledge Series: Disk Performance Hints & Tips

See here for the second entry in our "knowledge" series, providing hints & tips on KVM on z disk performance.

Webinar: OpenStack for KVM with Ubuntu on IBM z Systems

Abstract: This session is divided into three parts, each with an equal time share of 15-20 minutes. We will start with a recap what Infrastructure as a Service (IaaS) is all about to resolve some minor potential misconceptions. After that, an overview of the most important capabilities of OpenStack are shown. The most common (at least in the past) pain points and mitigations are discussed too. Eventually, after having enough context, we take a look at Ubuntu and OpenStack on z. This includes deployment, operations and supported features. This session will bring you benefit if you're new(-ish) to OpenStack, evaluating IaaS solutions, and care about the user/operators-view.

Speaker : Markus Zoeller, OpenStack Development, IBM Germany

Audience: IT Manager, IT Architects, System Administrators

Date: Wednesday, April 26th, 2017
Time: 11:00 AM EST / New York, 4:00 PM CET / Germany
Duration: 75 minutes

Registration: You can register here. After registering, you will receive a
confirmation email containing information about joining the webinar.

Replay & Archive: All sessions are recorded. For the archive as well as a replay and handout of this session (available by Apr 30, 2017) and all previous webcasts please visit http://www.vm.ibm.com/education/lvc/

Contact: Please direct any questions to Stephanie Gherghe at gherghe@de.ibm.com

KVM for IBM z Withdrawal

IBM announced that KVM for IBM z will be withdrawn, effective March 31, 2018. From the notice:

"KVM for IBM z Systems Version 1.1.2 will be the last release delivered by IBM. However, IBM will continue to provide the Linux and KVM enablement for z Systems [...]"

Make no mistake: The withdrawal only affects the product KVM for IBM z. It does not mean the end for KVM on z (our open source effort to support KVM on IBM z Systems). To the contrary, development will not only continue unaffected, but the options for users grow, especially with the recent addition of SuSE to the existing support in Ubuntu.
See the FAQ for further details.

SLES now supports KVM on z

SuSE has announced formal support for KVM on z starting with SLES 12 SP2. See the official announcement here for full details.

Knowledge Series: Choosing the Right Configuration

Large server setups are quite typical for KVM on z. One common pitfall is that system and application defaults that work well for a small number of servers may not work very well for a large number of virtual servers or in combination with huge host resources. The following sections present a list of snags that could happen, along with respective suggestions on how to resolve them.
Read more...

QEMU v2.8 & libvirt v3.0 released

QEMU v2.8 and libvirt v3.0 (available for download at the libvirt project website) are out! The highlight from a KVM on z perspective is the introduction of CPU models.
The CPU models are of primary use in live migration scenarios. For example, in a setup with different z Systems machine generations, it is now possible to check up-front whether the target host will support all facilities required by a guest for a successful migration. In case any of the required facilities are missing, the migration is aborted, and the guest will continue to run on the current host.
Furthermore, a guest can be defined with a backlevel CPU model compatible with the target machine (of a previous z Systems generation), so that migrations become possible.

To see what CPU models QEMU (and hence the host) supports, use virsh domcapabilities:

  $ virsh domcapabilities
    [...]
    <cpu>
      <mode name='custom' supported='yes'>
        <model usable='unknown'>z10EC-base</model>
        <model usable='unknown'>z9EC-base</model>
        <model usable='unknown'>z196.2-base</model>
        <model usable='unknown'>z900-base</model>
        <model usable='unknown'>z990</model>
        <model usable='unknown'>z900.2-base</model>
        <model usable='unknown'>host</model>
        <model usable='unknown'>z900.3</model>
        <model usable='unknown'>z114</model>
        <model usable='unknown'>z890-base</model>
        <model usable='unknown'>z13.2-base</model>
        <model usable='unknown'>zEC12.2</model>
        [...]

libvirt v.2.5.0 released

libvirt v2.5.0 is now available for download at the libvirt project website.
A highlight for the z Systems platform support in this release is scsi_host hostdev passthrough, improving throughput by providing a libvirt frontend for scsi_host devices.

New White Paper available: KVM Network Performance

A new white paper has been published: KVM Network Performance - Best Practices and Tuning Recommendations. It is available here, and explores different system configurations (running KVM guests), different networking configuration choices, as well as tuning recommendations for the KVM host and KVM guest environments to achieve greater network performance on the IBM z Systems platforms.