kvm-390: Let kernel exit SIE instruction on work

kvm-390: Let kernel exit SIE instruction on work

BugLink: http://bugs.launchpad.net/bugs/775809

commit 9ff4cfb3fcfd48b49fdd9be7381b3be340853aa4 upstream.

From: Christian Borntraeger <borntraeger@de.ibm.com>

This patch fixes the sie exit on interrupts. The low level
interrupt handler returns to the PSW address in pt_regs and not
to the PSW address in the lowcore.
Without this fix a cpu bound guest might never leave guest state
since the host interrupt handler would blindly return to the
SIE instruction, even on need_resched and friends.

Signed-off-by: Carsten Otte <cotte@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>