Implement gmap_protect_asce_top_level(), which was a stub. This
function was a stub due to cross dependencies with other patches.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
---
 arch/s390/kvm/gmap.c | 73 ++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 71 insertions(+), 2 deletions(-)

diff --git a/arch/s390/kvm/gmap.c b/arch/s390/kvm/gmap.c
index 29ce8df697dd..cbb777e940d1 100644
--- a/arch/s390/kvm/gmap.c
+++ b/arch/s390/kvm/gmap.c
@@ -22,6 +22,7 @@
 #include "dat.h"
 #include "gmap.h"
 #include "kvm-s390.h"
+#include "faultin.h"
 
 static inline bool kvm_s390_is_in_sie(struct kvm_vcpu *vcpu)
 {
@@ -988,10 +989,78 @@ static struct gmap *gmap_find_shadow(struct gmap *parent, union asce asce, int e
 	return NULL;
 }
 
+#define CRST_TABLE_PAGES (_CRST_TABLE_SIZE / PAGE_SIZE)
+struct gmap_protect_asce_top_level {
+	unsigned long seq;
+	struct guest_fault f[CRST_TABLE_PAGES];
+};
+
+static inline int __gmap_protect_asce_top_level(struct kvm_s390_mmu_cache *mc, struct gmap *sg,
+						struct gmap_protect_asce_top_level *context)
+{
+	int rc, i;
+
+	guard(write_lock)(&sg->kvm->mmu_lock);
+
+	if (kvm_s390_array_needs_retry_safe(sg->kvm, context->seq, context->f))
+		return -EAGAIN;
+
+	scoped_guard(spinlock, &sg->parent->children_lock) {
+		for (i = 0; i < CRST_TABLE_PAGES; i++) {
+			rc = gmap_protect_rmap(mc, sg, context->f[i].gfn, 0, context->f[i].pfn,
+					       TABLE_TYPE_REGION1 + 1, context->f[i].writable);
+			if (rc)
+				return rc;
+		}
+		sg->initialized = true;
+		gmap_add_child(sg->parent, sg);
+	}
+
+	kvm_s390_release_faultin_array(sg->kvm, context->f, false);
+	return 0;
+}
+
+static inline int _gmap_protect_asce_top_level(struct kvm_s390_mmu_cache *mc, struct gmap *sg,
+					       struct gmap_protect_asce_top_level *context)
+{
+	int rc;
+
+	if (kvm_s390_array_needs_retry_unsafe(sg->kvm, context->seq, context->f))
+		return -EAGAIN;
+	do {
+		rc = kvm_s390_mmu_cache_topup(mc);
+		if (rc)
+			return rc;
+		rc = radix_tree_preload(GFP_KERNEL);
+		if (rc)
+			return rc;
+		rc = __gmap_protect_asce_top_level(mc, sg, context);
+		radix_tree_preload_end();
+	} while (rc == -ENOMEM);
+
+	return rc;
+}
+
 static int gmap_protect_asce_top_level(struct kvm_s390_mmu_cache *mc, struct gmap *sg)
 {
-	KVM_BUG_ON(1, sg->kvm);
-	return -EINVAL;
+	struct gmap_protect_asce_top_level context = {};
+	union asce asce = sg->guest_asce;
+	int rc;
+
+	KVM_BUG_ON(!sg->is_shadow, sg->kvm);
+
+	context.seq = sg->kvm->mmu_invalidate_seq;
+	/* Pairs with the smp_wmb() in kvm_mmu_invalidate_end(). */
+	smp_rmb();
+
+	rc = kvm_s390_get_guest_pages(sg->kvm, context.f, asce.rsto, asce.dt + 1, false);
+	if (rc > 0)
+		rc = -EFAULT;
+	if (!rc)
+		rc = _gmap_protect_asce_top_level(mc, sg, &context);
+	if (rc)
+		kvm_s390_release_faultin_array(sg->kvm, context.f, true);
+	return rc;
 }
 
 /**
-- 
2.51.1