KVM: s390: Optimize ucontrol path
KVM: s390: Optimize ucontrol path

Since commit 7c470539c95630c1f2a10f109e96f249730b75eb
(s390/kvm: avoid automatic sie reentry) we will run through the C code
of KVM on host interrupts instead of just reentering the guest. This
will result in additional ucontrol exits (at least HZ per second). Let
handle a 0 intercept in the kernel and dont return to userspace,
even if in ucontrol mode.

Signed-off-by: Christian Borntraeger <49712f635b03c16d7f4c43df70e49ec8c565813d@de.ibm.com>
Reviewed-by: Cornelia Huck <94980dd689360e06f79e918bf71ea5fed7a2bc63@de.ibm.com>
CC: 4fbacc2fa0ffdbb11bf1ad6925b886ebd08dd15f@vger.kernel.org

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs