Kernel 4.0

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Kernel downloads for the "Development stream"

Download Description
upstream kernel 4.0 kernel 4.0 - upstream with feature descriptions.
linux-4.0-s390-message-catalog.tar.gz / MD5 "Development Stream" kernel 4.0 - message-catalog (optional)

2015-07-10: kernel 4.0 - upstream (feature description)

To download the linux-4.0.tar.gz visit:

The upstream kernel 4.0 contains the following functionality developed by the Linux on z Systems development team:

Simultaneous multithreading support
With this feature, the Linux kernel can use the simultaneous multithreading technology on mainframes.
This technology surfaces a single core as multiple CPUs. In Linux terms, simultaneous multithreading is known as SMT or Hyper-Threading.
SMT is supported on LPAR only. In addition s390-tools-1.30.0 is required with enhanced MT support for dump and hyptop.
For documentation see Device Drivers, Features, and Commands (with kernel 4.0), Chapter 23: 'Managing CPUs', Chapter 26: 's390 hypervisor file system', Chapter 54: 'Selected kernel parameters'.

Export diag 0c data with /sys/kernel/debug/s390_hypfs/diag_0c
With this feature, you can read the CPU performance metrics provided by the z/VM diagnose 0C (works on z/VM only).
This then allows to get the management time for each online CPU of the guest where the diagnose is executed.
For documentation see Device Drivers, Features, and Commands (with kernel 4.0), Chapter 53: 'Commands for Linux on z Systems', 'hyptop - Display hypervisor performance data'.

Avoid cache aliases on System z13
Improve the overall performance of user space applications on z13 by aligning shared objects to multiples of 512 KB.
The virtual addresses from multiple mappings for a page of a shared object needs to have identical bits in the range 2^12 to 2^18 to avoid cache aliases. Support on IBM z13 only.

Enable kdump for SMT
With this feature, you can create kernel dumps of Linux systems that make use of the multi-threading facility. Can be used on LPAR only.
For documentation see Using the Dump Tools, Chapter 1: 'Introduction', Version Dependencies.

Extend the generic cryptographic device driver (zcrypt) to exploit the IBM Crypto Express 5S adapter (CEX5S).
This feature extends the generic cryptographic device driver (zcrypt) to support the CEX5S adapter.
The CEX5S adapter is exposed as a CEX5A, CEX5C or CEX5P cryptographic device as of z13.
Following z/VM APAR is a mandatory prerequisite: VM65577: z/VM 6.2 and 6.3 Compatibility and crypto support (GA 2015-02-13)
For documentation see Device Drivers, Features, and Commands, Chapter Security, 'Generic cryptogaphic device driver'

Wildcard filter support for regulating access to HVC terminal devices.
You can use a simple wildcard for regulating access to HVC terminal devices.
Also you can use 'lnxhvc' as a generic terminal ID that maps to any free HVC terminal device.
For documentation see How to Set up a Terminal Server Environment on z/VM, Chapter 5 'Setting up the target systems'.

2015-07-10: "Development Stream" kernel 4.0 message catalog (feature - optional patch)

linux-4.0-s390-message-catalog.tar.gz / MD5 ... recommended (2015-07-10)

This patch contains:

Kernel message catalog.
Add support for automatic message tags to the printk macro families dev_xyz and pr_xyz. The message tag consists of a component name and a 24 bit hash of the message text. For each message that is documented in the included kernel message catalog a man page can be created with a script (which is included in the patch). The generated man pages contain explanatory text that is intended to help understand the messages.

Note that only s390 specific messages are prepared appropriately and included in the generated message catalog.

This patch is optional as it is very unlikely to be accepted in upstream kernel, but is recommended for all distributions which are built based on the 'Development stream'.