• Jiri Kosina's avatar
    x86/power: Fix 'nosmt' vs hibernation triple fault during resume · ec527c31
    Jiri Kosina authored
    As explained in
    
    	0cc3cd21 ("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    which is no longer valid.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: 4.19+ <stable@vger.kernel.org> # v4.19+
    Debugged-by: default avatarThomas Gleixner <tglx@linutronix.de>
    Fixes: 0cc3cd21 ("cpu/hotplug: Boot HT siblings at least once")
    Signed-off-by: default avatarJiri Kosina <jkosina@suse.cz>
    Acked-by: default avatarPavel Machek <pavel@ucw.cz>
    Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
    Reviewed-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
    Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
    ec527c31
cpu.h 7.18 KB