Public bug reported:
In the initial MIO support introduced in
commit 71ba41c9b1d9 ("s390/pci: provide support for MIO instructions")
setting up the PCI BAR resources defaults to using the
mio_wb address as the resource's start address.
This means users of the mapping, which includes most drivers, will get
write combining on PCI Stores.
his may lead to problems when drivers expect write through
behavior when not using an explicit ioremap_wc() which is the default
behavior on other platforms.
The attached patch changes the default to write through.
It has already been reviewed and is currently queued to be send for
Linux 5.6-rc5 with a CC stable tag.
** Affects: linux (Ubuntu)
Importance: Undecided
Assignee: Skipper Bug Screeners (skipper-screen-team)
Status: New
** Tags: architecture-s39064 bugnameltc-184193 severity-high
targetmilestone-inin2004
** Tags added: architecture-s39064 bugnameltc-184193 severity-high
targetmilestone-inin2004
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https://bugs.launchpad.net/bugs/1866162
Title:
[UBUNTU 20.04] ZPCI used write back addresses by default but should
use write through
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