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.
