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Description: s390/pci: move pseudo-MMIO to prevent MIO overlap
Symptom: On some configurations of z15 LPARs having an ISM device
attached may cause other PCI devices like NVMes or RoCEs to
be unusable and fail to probe. An error message in the kernel
log indicates that a PCI memory BAR could not be assigned.
Problem: On z15 with the enhanced PCI memory I/O instructions (MIO) ISM
devices still rely on the classic PCI instructions which used
pseud-MMIO addresses created by Linux. These addresses can
conflict with the firmware created MIO addresses which is
detected by the Linux PCI resource allocation code which then
prevents probing of the device even though technically the
address conflict would not cause issues.
Solution: Use disjunct ranges for Linux generated pseudo-MMIO and firmware
provided MIO addresses.
Reproduction: On an LPAR with a lot of PCI devices and in particular many ISM
devices the conflict is more likely. It is however unclear how
to provoke a conflict without special firmware. The fix was and
will be tested on a known affected system.
Upstream-ID: 52d04d408185b7aa47628d2339c28ec70074e0ae
Distros: Ubuntu 20.04 and higher
Preventive: yes
Author: Niklas Schnelle <schne...@linux.ibm.com>
Component: kernel
** Affects: linux (Ubuntu)
Importance: Undecided
Assignee: Skipper Bug Screeners (skipper-screen-team)
Status: New
** Tags: architecture-s39064 bugnameltc-196506 severity-high
targetmilestone-inin---
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[UBUNTU 20.04] s390/pci: move pseudo-MMIO to prevent MIO overlap
https://bugs.launchpad.net/bugs/1961850
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