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page-states.c

/*
 * arch/s390/mm/page-states.c
 *
 * Copyright IBM Corp. 2008
 *
 * Guest page hinting for unused pages.
 *
 * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
 */

#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/mm.h>
#include <linux/init.h>

#define ESSA_SET_STABLE       1
#define ESSA_SET_UNUSED       2

static int cmma_flag;

static int __init cmma(char *str)
{
      char *parm;
      parm = strstrip(str);
      if (strcmp(parm, "yes") == 0 || strcmp(parm, "on") == 0) {
            cmma_flag = 1;
            return 1;
      }
      cmma_flag = 0;
      if (strcmp(parm, "no") == 0 || strcmp(parm, "off") == 0)
            return 1;
      return 0;
}

__setup("cmma=", cmma);

void __init cmma_init(void)
{
      register unsigned long tmp asm("0") = 0;
      register int rc asm("1") = -EOPNOTSUPP;

      if (!cmma_flag)
            return;
      asm volatile(
            "       .insn rrf,0xb9ab0000,%1,%1,0,0\n"
            "0:     la      %0,0\n"
            "1:\n"
            EX_TABLE(0b,1b)
            : "+&d" (rc), "+&d" (tmp));
      if (rc)
            cmma_flag = 0;
}

void arch_free_page(struct page *page, int order)
{
      int i, rc;

      if (!cmma_flag)
            return;
      for (i = 0; i < (1 << order); i++)
            asm volatile(".insn rrf,0xb9ab0000,%0,%1,%2,0"
                       : "=&d" (rc)
                       : "a" ((page_to_pfn(page) + i) << PAGE_SHIFT),
                         "i" (ESSA_SET_UNUSED));
}

void arch_alloc_page(struct page *page, int order)
{
      int i, rc;

      if (!cmma_flag)
            return;
      for (i = 0; i < (1 << order); i++)
            asm volatile(".insn rrf,0xb9ab0000,%0,%1,%2,0"
                       : "=&d" (rc)
                       : "a" ((page_to_pfn(page) + i) << PAGE_SHIFT),
                         "i" (ESSA_SET_STABLE));
}

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