From: Christian Borntraeger <borntraeger@de.ibm.com>
Date: Thu, 6 Mar 2014 15:01:38 +0000 (+0100)
Subject: KVM: s390: Optimize ucontrol path
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=6d807fb1a3280648dffbdb78751d762d07048b5a;p=karo-tx-linux.git

KVM: s390: Optimize ucontrol path

commit 2955c83f72801245afd0fe5c560cc75b82bea9aa upstream.

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 <borntraeger@de.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index e0676f390d57..95f4a976c160 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -753,7 +753,8 @@ static int vcpu_post_run(struct kvm_vcpu *vcpu, int exit_reason)
 
 	if (rc == 0) {
 		if (kvm_is_ucontrol(vcpu->kvm))
-			rc = -EOPNOTSUPP;
+			/* Don't exit for host interrupts. */
+			rc = vcpu->arch.sie_block->icptcode ? -EOPNOTSUPP : 0;
 		else
 			rc = kvm_handle_sie_intercept(vcpu);
 	}