Changes/z13BaselineForIBMZ

z13 as the Baseline for IBM Z Hardware

Summary

Move the minimal architecture level for IBM Z hardware (the s390x architecture) to z13 to benefit from the new features and better performance in the newer CPU.

Owner

• Name: Dan Horák
• Email: <sharkcz@fedoraproject.org>

Current status

• Targeted release: Fedora Linux 38
• Last updated: 2022-08-03
• devel thread
• FESCo issue: #2842
• Tracker bug: #2115105
• Release notes tracker: #872

Detailed Description

Moving the minimal architecture level for IBM Z hardware (the s390x architecture) to z13 allows us to benefit from the new features and better performance in the newer CPU. The current minimum at zEC12 is targeting hardware that has been already obsoleted by the vendor. All Fedora infrastructure is already using the latest z15 hardware (builders and co and also our public resources for developers). But we still want to be able to use existing z13 and z14 hardware. Also the TCG (full-system/non-KVM) emulation in QEMU already allows running distros built with z13 as the baseline architecture. This change means updating the defaults in gcc and the build flags and in the kernel.

Benefit to Fedora

The primary benefit is being able to exploit vector instructions by default, which should increase performance. Plus take advantage of other architectural improvements.

Scope

• Proposal owners:
  • update the minimal hardware level in the kernel config to z13 (MR#1907)
  • set default compiler flags to -march=z13 -mtune=z14 in redhat-rpm-config (PR#207) and gcc (PR#25)

• Other developers:

none

• Release engineering: #Releng issue number

• Policies and guidelines: N/A (not needed for this Change)

• Trademark approval: N/A (not needed for this Change)

• Alignment with Objectives:

Upgrade/compatibility impact

Users with hardware older than z13 should stick with F-36 or older release.

How To Test

You shouldn't be able to start Fedora Linux 37 on system older than z13.

User Experience

The primary difference will be in the availability of the vector instructions and as a result better performance.

Contingency Plan

• Contingency mechanism: (What to do? Who will do it?) N/A (not a System Wide Change)
• Contingency deadline: N/A (not a System Wide Change)
• Blocks release? N/A (not a System Wide Change), Yes/No

Documentation

N/A (not a System Wide Change)

Release Notes

Starting with Fedora Linux 37 the minimal hardware level for the s390x architecture has been updated to z13.