On Thu 2019-05-30 00:09:39, Jiri Kosina wrote: > From: Jiri Kosina <[email protected]> > > As explained in > > 0cc3cd21657b ("cpu/hotplug: Boot HT siblings at least once") > > we always, no matter what, have to bring up x86 HT siblings during boot at > least once in order to avoid first MCE bringing the system to its knees. > > That means that whenever 'nosmt' is supplied on the kernel command-line, > all the HT siblings are as a result sitting in mwait or cpudile after > going through the online-offline cycle at least once. > > This causes a serious issue though when a kernel, which saw 'nosmt' on its > commandline, is going to perform resume from hibernation: if the resume > from the hibernated image is successful, cr3 is flipped in order to point > to the address space of the kernel that is being resumed, which in turn > means that all the HT siblings are all of a sudden mwaiting on address > which is no longer valid. > > That results in triple fault shortly after cr3 is switched, and machine > reboots. > > Fix this by always waking up all the SMT siblings before initiating the > 'restore from hibernation' process; this guarantees that all the HT > siblings will be properly carried over to the resumed kernel waiting in > resume_play_dead(), and acted upon accordingly afterwards, based on the > target kernel configuration. > Symmetricaly, the resumed kernel has to push the SMT siblings to mwait > again in case it has SMT disabled; this means it has to online all > the siblings when resuming (so that they come out of hlt) and offline > them again to let them reach mwait. > > Cc: [email protected] # v4.19+ > Debugged-by: Thomas Gleixner <[email protected]> > Fixes: 0cc3cd21657b ("cpu/hotplug: Boot HT siblings at least once") > Signed-off-by: Jiri Kosina <[email protected]>
Acked-by: Pavel Machek <[email protected]> -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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