From 684135e0962fce7946a89f50cf6c7ffa78a11b09 Mon Sep 17 00:00:00 2001
From: Thomas Huth <thuth@linux.vnet.ibm.com>
Date: Thu, 17 Apr 2014 09:57:10 +0200
Subject: KVM: s390: Avoid endless loops of specification exceptions

If the new PSW for program interrupts is invalid, the VM ends up
in an endless loop of specification exceptions. Since there is not
much left we can do in this case, we should better drop to userspace
instead so that the crash can be reported to the user.

Signed-off-by: Thomas Huth <thuth@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

diff --git a/arch/s390/kvm/intercept.c b/arch/s390/kvm/intercept.c
index bd607cf..ddc69f5 100644
--- a/arch/s390/kvm/intercept.c
+++ b/arch/s390/kvm/intercept.c
@@ -195,6 +195,7 @@ static int handle_itdb(struct kvm_vcpu *vcpu)
 static int handle_prog(struct kvm_vcpu *vcpu)
 {
 	struct kvm_s390_pgm_info pgm_info;
+	psw_t psw;
 	int rc;
 
 	vcpu->stat.exit_program_interruption++;
@@ -207,7 +208,14 @@ static int handle_prog(struct kvm_vcpu *vcpu)
 	}
 
 	trace_kvm_s390_intercept_prog(vcpu, vcpu->arch.sie_block->iprcc);
-
+	if (vcpu->arch.sie_block->iprcc == PGM_SPECIFICATION) {
+		rc = read_guest_lc(vcpu, __LC_PGM_NEW_PSW, &psw, sizeof(psw_t));
+		if (rc)
+			return rc;
+		/* Avoid endless loops of specification exceptions */
+		if (!is_valid_psw(&psw))
+			return -EOPNOTSUPP;
+	}
 	rc = handle_itdb(vcpu);
 	if (rc)
 		return rc;
-- 
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