KVM: s390: pv: Mark mm as protected after the set secure parameters and improve cleanup

We can only have protected guest pages after a successful set secure
parameters call as only then the UV allows imports and unpacks.

By moving the test we can now also check for it in s390_reset_acc()
and do an early return if it is 0.
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Fixes: 29b40f10 ("KVM: s390: protvirt: Add initial vm and cpu lifecycle handling")
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

arch/s390/kvm/kvm-s390.c

@@ -2312,7 +2312,7 @@ static int kvm_s390_handle_pv(struct kvm *kvm, struct kvm_pv_cmd *cmd)
 		struct kvm_s390_pv_unp unp = {};
 
 		r = -EINVAL;
-		if (!kvm_s390_pv_is_protected(kvm))
+		if (!kvm_s390_pv_is_protected(kvm) || !mm_is_protected(kvm->mm))
 			break;
 
 		r = -EFAULT;

arch/s390/kvm/pv.c

@@ -208,7 +208,6 @@ int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
 		return -EIO;
 	}
 	kvm->arch.gmap->guest_handle = uvcb.guest_handle;
-	atomic_set(&kvm->mm->context.is_protected, 1);
 	return 0;
 }
 
@@ -228,6 +227,8 @@ int kvm_s390_pv_set_sec_parms(struct kvm *kvm, void *hdr, u64 length, u16 *rc,
 	*rrc = uvcb.header.rrc;
 	KVM_UV_EVENT(kvm, 3, "PROTVIRT VM SET PARMS: rc %x rrc %x",
 		     *rc, *rrc);
+	if (!cc)
+		atomic_set(&kvm->mm->context.is_protected, 1);
 	return cc ? -EINVAL : 0;
 }
 

arch/s390/mm/gmap.c

@@ -2690,6 +2690,8 @@ static const struct mm_walk_ops reset_acc_walk_ops = {
 #include <linux/sched/mm.h>
 void s390_reset_acc(struct mm_struct *mm)
 {
+	if (!mm_is_protected(mm))
+		return;
 	/*
 	 * we might be called during
 	 * reset:                             we walk the pages and clear