s390/mm: provide base_asce_alloc() / base_asce_free() helper functions

Provide base_asce_alloc() and base_asce_free() helper functions which
can be used to allocate an ASCE and all required region, segment and
page tables required to access memory regions of the virtual kernel
address space.

Both, the ASCE and all tables, do not use any features that correspond
to e.g. enhanced DAT features. This is required for some I/O functions
that pass an ASCE, like e.g. some service call requests, but which may
not use any enhanced features.

Acked-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Acked-by: Janosch Frank <frankja@linux.vnet.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/pgalloc.h

@@ -151,4 +151,7 @@ void vmem_map_init(void);
 void *vmem_crst_alloc(unsigned long val);
 pte_t *vmem_pte_alloc(void);
 
+unsigned long base_asce_alloc(unsigned long addr, unsigned long num_pages);
+void base_asce_free(unsigned long asce);
+
 #endif /* _S390_PGALLOC_H */

arch/s390/mm/pgalloc.c

@@ -6,8 +6,9 @@
  *    Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
  */
 
-#include <linux/mm.h>
 #include <linux/sysctl.h>
+#include <linux/slab.h>
+#include <linux/mm.h>
 #include <asm/mmu_context.h>
 #include <asm/pgalloc.h>
 #include <asm/gmap.h>
@@ -366,3 +367,293 @@ void tlb_remove_table(struct mmu_gather *tlb, void *table)
 	if ((*batch)->nr == MAX_TABLE_BATCH)
 		tlb_flush_mmu(tlb);
 }
+
+/*
+ * Base infrastructure required to generate basic asces, region, segment,
+ * and page tables that do not make use of enhanced features like EDAT1.
+ */
+
+static struct kmem_cache *base_pgt_cache;
+
+static unsigned long base_pgt_alloc(void)
+{
+	u64 *table;
+
+	table = kmem_cache_alloc(base_pgt_cache, GFP_KERNEL);
+	if (table)
+		memset64(table, _PAGE_INVALID, PTRS_PER_PTE);
+	return (unsigned long) table;
+}
+
+static void base_pgt_free(unsigned long table)
+{
+	kmem_cache_free(base_pgt_cache, (void *) table);
+}
+
+static unsigned long base_crst_alloc(unsigned long val)
+{
+	unsigned long table;
+
+	table =	 __get_free_pages(GFP_KERNEL, CRST_ALLOC_ORDER);
+	if (table)
+		crst_table_init((unsigned long *)table, val);
+	return table;
+}
+
+static void base_crst_free(unsigned long table)
+{
+	free_pages(table, CRST_ALLOC_ORDER);
+}
+
+#define BASE_ADDR_END_FUNC(NAME, SIZE)					\
+static inline unsigned long base_##NAME##_addr_end(unsigned long addr,	\
+						   unsigned long end)	\
+{									\
+	unsigned long next = (addr + (SIZE)) & ~((SIZE) - 1);		\
+									\
+	return (next - 1) < (end - 1) ? next : end;			\
+}
+
+BASE_ADDR_END_FUNC(page,    _PAGE_SIZE)
+BASE_ADDR_END_FUNC(segment, _SEGMENT_SIZE)
+BASE_ADDR_END_FUNC(region3, _REGION3_SIZE)
+BASE_ADDR_END_FUNC(region2, _REGION2_SIZE)
+BASE_ADDR_END_FUNC(region1, _REGION1_SIZE)
+
+static inline unsigned long base_lra(unsigned long address)
+{
+	unsigned long real;
+
+	asm volatile(
+		"	lra	%0,0(%1)\n"
+		: "=d" (real) : "a" (address) : "cc");
+	return real;
+}
+
+static int base_page_walk(unsigned long origin, unsigned long addr,
+			  unsigned long end, int alloc)
+{
+	unsigned long *pte, next;
+
+	if (!alloc)
+		return 0;
+	pte = (unsigned long *) origin;
+	pte += (addr & _PAGE_INDEX) >> _PAGE_SHIFT;
+	do {
+		next = base_page_addr_end(addr, end);
+		*pte = base_lra(addr);
+	} while (pte++, addr = next, addr < end);
+	return 0;
+}
+
+static int base_segment_walk(unsigned long origin, unsigned long addr,
+			     unsigned long end, int alloc)
+{
+	unsigned long *ste, next, table;
+	int rc;
+
+	ste = (unsigned long *) origin;
+	ste += (addr & _SEGMENT_INDEX) >> _SEGMENT_SHIFT;
+	do {
+		next = base_segment_addr_end(addr, end);
+		if (*ste & _SEGMENT_ENTRY_INVALID) {
+			if (!alloc)
+				continue;
+			table = base_pgt_alloc();
+			if (!table)
+				return -ENOMEM;
+			*ste = table | _SEGMENT_ENTRY;
+		}
+		table = *ste & _SEGMENT_ENTRY_ORIGIN;
+		rc = base_page_walk(table, addr, next, alloc);
+		if (rc)
+			return rc;
+		if (!alloc)
+			base_pgt_free(table);
+		cond_resched();
+	} while (ste++, addr = next, addr < end);
+	return 0;
+}
+
+static int base_region3_walk(unsigned long origin, unsigned long addr,
+			     unsigned long end, int alloc)
+{
+	unsigned long *rtte, next, table;
+	int rc;
+
+	rtte = (unsigned long *) origin;
+	rtte += (addr & _REGION3_INDEX) >> _REGION3_SHIFT;
+	do {
+		next = base_region3_addr_end(addr, end);
+		if (*rtte & _REGION_ENTRY_INVALID) {
+			if (!alloc)
+				continue;
+			table = base_crst_alloc(_SEGMENT_ENTRY_EMPTY);
+			if (!table)
+				return -ENOMEM;
+			*rtte = table | _REGION3_ENTRY;
+		}
+		table = *rtte & _REGION_ENTRY_ORIGIN;
+		rc = base_segment_walk(table, addr, next, alloc);
+		if (rc)
+			return rc;
+		if (!alloc)
+			base_crst_free(table);
+	} while (rtte++, addr = next, addr < end);
+	return 0;
+}
+
+static int base_region2_walk(unsigned long origin, unsigned long addr,
+			     unsigned long end, int alloc)
+{
+	unsigned long *rste, next, table;
+	int rc;
+
+	rste = (unsigned long *) origin;
+	rste += (addr & _REGION2_INDEX) >> _REGION2_SHIFT;
+	do {
+		next = base_region2_addr_end(addr, end);
+		if (*rste & _REGION_ENTRY_INVALID) {
+			if (!alloc)
+				continue;
+			table = base_crst_alloc(_REGION3_ENTRY_EMPTY);
+			if (!table)
+				return -ENOMEM;
+			*rste = table | _REGION2_ENTRY;
+		}
+		table = *rste & _REGION_ENTRY_ORIGIN;
+		rc = base_region3_walk(table, addr, next, alloc);
+		if (rc)
+			return rc;
+		if (!alloc)
+			base_crst_free(table);
+	} while (rste++, addr = next, addr < end);
+	return 0;
+}
+
+static int base_region1_walk(unsigned long origin, unsigned long addr,
+			     unsigned long end, int alloc)
+{
+	unsigned long *rfte, next, table;
+	int rc;
+
+	rfte = (unsigned long *) origin;
+	rfte += (addr & _REGION1_INDEX) >> _REGION1_SHIFT;
+	do {
+		next = base_region1_addr_end(addr, end);
+		if (*rfte & _REGION_ENTRY_INVALID) {
+			if (!alloc)
+				continue;
+			table = base_crst_alloc(_REGION2_ENTRY_EMPTY);
+			if (!table)
+				return -ENOMEM;
+			*rfte = table | _REGION1_ENTRY;
+		}
+		table = *rfte & _REGION_ENTRY_ORIGIN;
+		rc = base_region2_walk(table, addr, next, alloc);
+		if (rc)
+			return rc;
+		if (!alloc)
+			base_crst_free(table);
+	} while (rfte++, addr = next, addr < end);
+	return 0;
+}
+
+/**
+ * base_asce_free - free asce and tables returned from base_asce_alloc()
+ * @asce: asce to be freed
+ *
+ * Frees all region, segment, and page tables that were allocated with a
+ * corresponding base_asce_alloc() call.
+ */
+void base_asce_free(unsigned long asce)
+{
+	unsigned long table = asce & _ASCE_ORIGIN;
+
+	if (!asce)
+		return;
+	switch (asce & _ASCE_TYPE_MASK) {
+	case _ASCE_TYPE_SEGMENT:
+		base_segment_walk(table, 0, _REGION3_SIZE, 0);
+		break;
+	case _ASCE_TYPE_REGION3:
+		base_region3_walk(table, 0, _REGION2_SIZE, 0);
+		break;
+	case _ASCE_TYPE_REGION2:
+		base_region2_walk(table, 0, _REGION1_SIZE, 0);
+		break;
+	case _ASCE_TYPE_REGION1:
+		base_region1_walk(table, 0, -_PAGE_SIZE, 0);
+		break;
+	}
+	base_crst_free(table);
+}
+
+static int base_pgt_cache_init(void)
+{
+	static DEFINE_MUTEX(base_pgt_cache_mutex);
+	unsigned long sz = _PAGE_TABLE_SIZE;
+
+	if (base_pgt_cache)
+		return 0;
+	mutex_lock(&base_pgt_cache_mutex);
+	if (!base_pgt_cache)
+		base_pgt_cache = kmem_cache_create("base_pgt", sz, sz, 0, NULL);
+	mutex_unlock(&base_pgt_cache_mutex);
+	return base_pgt_cache ? 0 : -ENOMEM;
+}
+
+/**
+ * base_asce_alloc - create kernel mapping without enhanced DAT features
+ * @addr: virtual start address of kernel mapping
+ * @num_pages: number of consecutive pages
+ *
+ * Generate an asce, including all required region, segment and page tables,
+ * that can be used to access the virtual kernel mapping. The difference is
+ * that the returned asce does not make use of any enhanced DAT features like
+ * e.g. large pages. This is required for some I/O functions that pass an
+ * asce, like e.g. some service call requests.
+ *
+ * Note: the returned asce may NEVER be attached to any cpu. It may only be
+ *	 used for I/O requests. tlb entries that might result because the
+ *	 asce was attached to a cpu won't be cleared.
+ */
+unsigned long base_asce_alloc(unsigned long addr, unsigned long num_pages)
+{
+	unsigned long asce, table, end;
+	int rc;
+
+	if (base_pgt_cache_init())
+		return 0;
+	end = addr + num_pages * PAGE_SIZE;
+	if (end <= _REGION3_SIZE) {
+		table = base_crst_alloc(_SEGMENT_ENTRY_EMPTY);
+		if (!table)
+			return 0;
+		rc = base_segment_walk(table, addr, end, 1);
+		asce = table | _ASCE_TYPE_SEGMENT | _ASCE_TABLE_LENGTH;
+	} else if (end <= _REGION2_SIZE) {
+		table = base_crst_alloc(_REGION3_ENTRY_EMPTY);
+		if (!table)
+			return 0;
+		rc = base_region3_walk(table, addr, end, 1);
+		asce = table | _ASCE_TYPE_REGION3 | _ASCE_TABLE_LENGTH;
+	} else if (end <= _REGION1_SIZE) {
+		table = base_crst_alloc(_REGION2_ENTRY_EMPTY);
+		if (!table)
+			return 0;
+		rc = base_region2_walk(table, addr, end, 1);
+		asce = table | _ASCE_TYPE_REGION2 | _ASCE_TABLE_LENGTH;
+	} else {
+		table = base_crst_alloc(_REGION1_ENTRY_EMPTY);
+		if (!table)
+			return 0;
+		rc = base_region1_walk(table, addr, end, 1);
+		asce = table | _ASCE_TYPE_REGION1 | _ASCE_TABLE_LENGTH;
+	}
+	if (rc) {
+		base_asce_free(asce);
+		asce = 0;
+	}
+	return asce;
+}