Add page table management functions to be used for KVM guest (gmap)
page tables.

This patch adds the boilerplate and functions for the allocation and
deallocation of DAT tables.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
---
 arch/s390/kvm/Makefile     |  1 +
 arch/s390/kvm/dat.c        | 91 ++++++++++++++++++++++++++++++++++++++
 arch/s390/kvm/dat.h        |  4 ++
 arch/s390/mm/page-states.c |  1 +
 4 files changed, 97 insertions(+)
 create mode 100644 arch/s390/kvm/dat.c

diff --git a/arch/s390/kvm/Makefile b/arch/s390/kvm/Makefile
index 9a723c48b05a..84315d2f75fb 100644
--- a/arch/s390/kvm/Makefile
+++ b/arch/s390/kvm/Makefile
@@ -9,6 +9,7 @@ ccflags-y := -Ivirt/kvm -Iarch/s390/kvm
 
 kvm-y += kvm-s390.o intercept.o interrupt.o priv.o sigp.o
 kvm-y += diag.o gaccess.o guestdbg.o vsie.o pv.o gmap-vsie.o
+kvm-y += dat.o
 
 kvm-$(CONFIG_VFIO_PCI_ZDEV_KVM) += pci.o
 obj-$(CONFIG_KVM) += kvm.o
diff --git a/arch/s390/kvm/dat.c b/arch/s390/kvm/dat.c
new file mode 100644
index 000000000000..326be78adcda
--- /dev/null
+++ b/arch/s390/kvm/dat.c
@@ -0,0 +1,91 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  KVM guest address space mapping code
+ *
+ *    Copyright IBM Corp. 2007, 2020, 2024
+ *    Author(s): Claudio Imbrenda <imbrenda@linux.ibm.com>
+ *		 Martin Schwidefsky <schwidefsky@de.ibm.com>
+ *		 David Hildenbrand <david@redhat.com>
+ *		 Janosch Frank <frankja@linux.ibm.com>
+ */
+
+#include <linux/kernel.h>
+#include <linux/pagewalk.h>
+#include <linux/swap.h>
+#include <linux/smp.h>
+#include <linux/spinlock.h>
+#include <linux/slab.h>
+#include <linux/swapops.h>
+#include <linux/ksm.h>
+#include <linux/mm.h>
+#include <linux/mman.h>
+#include <linux/pgtable.h>
+#include <linux/kvm_types.h>
+#include <linux/kvm_host.h>
+
+#include <asm/pgalloc.h>
+#include <asm/page-states.h>
+#include <asm/tlb.h>
+#include "dat.h"
+
+static inline struct page_table *dat_alloc_pt_noinit(void)
+{
+	struct page *page;
+	void *virt;
+
+	page = alloc_pages(GFP_ATOMIC, 0);
+	if (!page)
+		return NULL;
+
+	virt = page_to_virt(page);
+	__arch_set_page_dat(virt, 1);
+	return virt;
+}
+
+struct page_table *dat_alloc_pt(unsigned long pte_bits, unsigned long pgste_bits)
+{
+	struct page_table *res;
+
+	res = dat_alloc_pt_noinit();
+	if (res)
+		dat_init_page_table(res, pte_bits, pgste_bits);
+	return res;
+}
+
+static inline struct crst_table *dat_alloc_crst_noinit(void)
+{
+	struct page *page;
+	void *virt;
+
+	page = alloc_pages(GFP_ATOMIC | __GFP_COMP, CRST_ALLOC_ORDER);
+	if (!page)
+		return NULL;
+	virt = page_to_virt(page);
+	__arch_set_page_dat(virt, 1UL << CRST_ALLOC_ORDER);
+	return virt;
+}
+
+struct crst_table *dat_alloc_crst(unsigned long init)
+{
+	struct crst_table *res;
+
+	res = dat_alloc_crst_noinit();
+	if (res)
+		crst_table_init((void *)res, init);
+	return res;
+}
+
+void dat_free_level(struct crst_table *table, bool owns_ptes)
+{
+	unsigned int i;
+
+	for (i = 0; i < _CRST_ENTRIES; i++) {
+		if (table->crstes[i].h.fc || table->crstes[i].h.i)
+			continue;
+		if (!is_pmd(table->crstes[i]))
+			dat_free_level(dereference_crste(table->crstes[i]), owns_ptes);
+		else if (owns_ptes)
+			dat_free_pt(dereference_pmd(table->crstes[i].pmd));
+	}
+	dat_free_crst(table);
+}
diff --git a/arch/s390/kvm/dat.h b/arch/s390/kvm/dat.h
index 1e355239247b..5056cfa02619 100644
--- a/arch/s390/kvm/dat.h
+++ b/arch/s390/kvm/dat.h
@@ -385,6 +385,10 @@ static inline union crste _crste_fc1(kvm_pfn_t pfn, int tt, bool w, bool d)
 	return res;
 }
 
+void dat_free_level(struct crst_table *table, bool owns_ptes);
+struct page_table *dat_alloc_pt(unsigned long pte_bits, unsigned long pgste_bits);
+struct crst_table *dat_alloc_crst(unsigned long init);
+
 static inline struct crst_table *crste_table_start(union crste *crstep)
 {
 	return (struct crst_table *)ALIGN_DOWN((unsigned long)crstep, _CRST_TABLE_SIZE);
diff --git a/arch/s390/mm/page-states.c b/arch/s390/mm/page-states.c
index 01f9b39e65f5..5bee173db72e 100644
--- a/arch/s390/mm/page-states.c
+++ b/arch/s390/mm/page-states.c
@@ -13,6 +13,7 @@
 #include <asm/page.h>
 
 int __bootdata_preserved(cmma_flag);
+EXPORT_SYMBOL(cmma_flag);
 
 void arch_free_page(struct page *page, int order)
 {
-- 
2.51.0