** Information type changed from Proprietary to Public
** Also affects: linux (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1729442
Title:
Prevent timer value 0 for MWAITX
Status in amd:
New
Status in linux package in Ubuntu:
New
Bug description:
Newer hardware has uncovered a bug in the software implementation of
using MWAITX for the delay function. A value of 0 for the timer is
meant to indicate that a timeout will not be used to exit MWAITX. On
newer hardware this can result in MWAITX never returning, resulting in
NMI soft lockup messages being printed. On older hardware, some of the
other conditions under which MWAITX can exit masked this issue.
The AMD APM does not currently document this and will be updated.
Please refer to http://marc.info/?l=kvm&m=148950623231140 for
information regarding NMI soft lockup messages on an AMD Ryzen 1800X.
This has been root-caused as a 0 passed to MWAITX causing it to wait
indefinitely. This change has the added benefit of avoiding the
unnecessary setup of MONITORX/MWAITX when the delay value is zero.
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit/?id=88d879d29f9cc0de2d930b584285638cdada6625
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