[S390] kvm-390: Let kernel exit SIE instruction on work

[S390] kvm-390: Let kernel exit SIE instruction on work

From: Christian Borntraeger <[email protected]>

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.

Cc: [email protected]
Signed-off-by: Carsten Otte <[email protected]>
Signed-off-by: Christian Borntraeger <[email protected]>
Signed-off-by: Martin Schwidefsky <[email protected]>