[PATCH v2] KVM: s390: take care of clock-comparator sign control

[David Hildenbrand <david@redhat.com>]

Missed when enabling the Multiple-epoch facility. If the facility is
installed and the control is set, a sign based comaprison has to be
performed.

Right now we would inject wrong interrupts and ignore interrupt
conditions. Also the sleep time is calculated in a wrong way.

Signed-off-by: David Hildenbrand <david@redhat.com>
---

We might be able to drop the checks for "test_kvm_facility(vcpu->kvm, 139)",
as the architecture states:

"When the multiple-epoch facility is not installed in the configuration
and the clock-comparator sign control is one, it is unpredictable whether
the comparison follows the rules of unsigned or signed binary arithmetic."

Have no machine to test this with :(

 arch/s390/kvm/interrupt.c | 32 ++++++++++++++++++++++++++------
 1 file changed, 26 insertions(+), 6 deletions(-)

diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index 024ad8bcc516..6566a853c0b8 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -170,7 +170,16 @@ static int ckc_interrupts_enabled(struct kvm_vcpu *vcpu)
 
 static int ckc_irq_pending(struct kvm_vcpu *vcpu)
 {
-	if (vcpu->arch.sie_block->ckc >= kvm_s390_get_tod_clock_fast(vcpu->kvm))
+	int64_t ckc, tod;
+
+	if (vcpu->arch.sie_block->gcr[0] & 0x0020000000000000ul &&
+	    test_kvm_facility(vcpu->kvm, 139)) {
+		ckc = vcpu->arch.sie_block->ckc;
+		tod = kvm_s390_get_tod_clock_fast(vcpu->kvm);
+		if (ckc >= tod)
+			return 0;
+	} else if (vcpu->arch.sie_block->ckc >=
+		   kvm_s390_get_tod_clock_fast(vcpu->kvm))
 		return 0;
 	return ckc_interrupts_enabled(vcpu);
 }
@@ -1011,13 +1020,24 @@ int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu)
 
 static u64 __calculate_sltime(struct kvm_vcpu *vcpu)
 {
-	u64 now, cputm, sltime = 0;
+	u64 now, cputm, ckc, sltime = 0;
+	int64_t ckc_signed, now_signed;
 
 	if (ckc_interrupts_enabled(vcpu)) {
-		now = kvm_s390_get_tod_clock_fast(vcpu->kvm);
-		sltime = tod_to_ns(vcpu->arch.sie_block->ckc - now);
-		/* already expired or overflow? */
-		if (!sltime || vcpu->arch.sie_block->ckc <= now)
+		if (vcpu->arch.sie_block->gcr[0] & 0x0020000000000000ul &&
+		    test_kvm_facility(vcpu->kvm, 139)) {
+			now = kvm_s390_get_tod_clock_fast(vcpu->kvm);
+			ckc = vcpu->arch.sie_block->ckc;
+			if (ckc < now)
+				sltime = tod_to_ns(now - ckc);
+		} else {
+			now_signed = kvm_s390_get_tod_clock_fast(vcpu->kvm);
+			ckc_signed = vcpu->arch.sie_block->ckc;
+			if (ckc_signed < now_signed)
+				sltime = tod_to_ns(now_signed - ckc_signed);
+		}
+		/* already expired */
+		if (!sltime)
 			return 0;
 		if (cpu_timer_interrupts_enabled(vcpu)) {
 			cputm = kvm_s390_get_cpu_timer(vcpu);
-- 
2.14.3