KVM: s390: implement KVM_REQ_TLB_FLUSH and make use of it

Use the KVM_REQ_TLB_FLUSH request in order to trigger tlb flushes instead
of manipulating the SIE control block whenever we need it. Also trigger it for
a control register sync directly instead of (ab)using kvm_s390_set_prefix().
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

arch/s390/kvm/kvm-s390.c

@@ -1051,6 +1051,11 @@ static int kvm_s390_handle_requests(struct kvm_vcpu *vcpu)
 		goto retry;
 	}
 
+	if (kvm_check_request(KVM_REQ_TLB_FLUSH, vcpu)) {
+		vcpu->arch.sie_block->ihcpu = 0xffff;
+		goto retry;
+	}
+
 	if (kvm_check_request(KVM_REQ_ENABLE_IBS, vcpu)) {
 		if (!ibs_enabled(vcpu)) {
 			trace_kvm_s390_enable_disable_ibs(vcpu->vcpu_id, 1);
@@ -1306,7 +1311,8 @@ static void sync_regs(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 		kvm_s390_set_prefix(vcpu, kvm_run->s.regs.prefix);
 	if (kvm_run->kvm_dirty_regs & KVM_SYNC_CRS) {
 		memcpy(&vcpu->arch.sie_block->gcr, &kvm_run->s.regs.crs, 128);
-		kvm_s390_set_prefix(vcpu, kvm_run->s.regs.prefix);
+		/* some control register changes require a tlb flush */
+		kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
 	}
 	if (kvm_run->kvm_dirty_regs & KVM_SYNC_ARCH0) {
 		vcpu->arch.sie_block->cputm = kvm_run->s.regs.cputm;
@@ -1519,7 +1525,7 @@ void kvm_s390_vcpu_start(struct kvm_vcpu *vcpu)
 	 * Another VCPU might have used IBS while we were offline.
 	 * Let's play safe and flush the VCPU at startup.
 	 */
-	vcpu->arch.sie_block->ihcpu  = 0xffff;
+	kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
 	spin_unlock(&vcpu->kvm->arch.start_stop_lock);
 	return;
 }

arch/s390/kvm/kvm-s390.h

@@ -70,7 +70,7 @@ static inline u32 kvm_s390_get_prefix(struct kvm_vcpu *vcpu)
 static inline void kvm_s390_set_prefix(struct kvm_vcpu *vcpu, u32 prefix)
 {
 	vcpu->arch.sie_block->prefix = prefix >> GUEST_PREFIX_SHIFT;
-	vcpu->arch.sie_block->ihcpu  = 0xffff;
+	kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
 	kvm_make_request(KVM_REQ_MMU_RELOAD, vcpu);
 }