text: #ifndef _ASM_X86_XEN_PAGE_H
  #define _ASM_X86_XEN_PAGE_H
  
  #include <linux/kernel.h>
  #include <linux/types.h>
  #include <linux/spinlock.h>
  #include <linux/pfn.h>
  #include <linux/mm.h>
  
  #include <asm/uaccess.h>
  #include <asm/page.h>
  #include <asm/pgtable.h>
  
  #include <xen/interface/xen.h>
  #include <xen/grant_table.h>
  #include <xen/features.h>
  
  /* Xen machine address */
  typedef struct xmaddr {
  	phys_addr_t maddr;
  } xmaddr_t;
  
  /* Xen pseudo-physical address */
  typedef struct xpaddr {
  	phys_addr_t paddr;
  } xpaddr_t;
  
  #define XMADDR(x)	((xmaddr_t) { .maddr = (x) })
  #define XPADDR(x)	((xpaddr_t) { .paddr = (x) })
  
  /**** MACHINE <-> PHYSICAL CONVERSION MACROS ****/
  #define INVALID_P2M_ENTRY	(~0UL)
  #define FOREIGN_FRAME_BIT	(1UL<<(BITS_PER_LONG-1))
  #define IDENTITY_FRAME_BIT	(1UL<<(BITS_PER_LONG-2))
  #define FOREIGN_FRAME(m)	((m) | FOREIGN_FRAME_BIT)
  #define IDENTITY_FRAME(m)	((m) | IDENTITY_FRAME_BIT)
  
  /* Maximum amount of memory we can handle in a domain in pages */
  #define MAX_DOMAIN_PAGES						\
      ((unsigned long)((u64)CONFIG_XEN_MAX_DOMAIN_MEMORY * 1024 * 1024 * 1024 / PAGE_SIZE))
  
  extern unsigned long *machine_to_phys_mapping;
  extern unsigned long  machine_to_phys_nr;
  extern unsigned long *xen_p2m_addr;
  extern unsigned long  xen_p2m_size;
  extern unsigned long  xen_max_p2m_pfn;
  
  extern unsigned long get_phys_to_machine(unsigned long pfn);
  extern bool set_phys_to_machine(unsigned long pfn, unsigned long mfn);
  extern bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn);
  extern unsigned long set_phys_range_identity(unsigned long pfn_s,
  					     unsigned long pfn_e);
  
  extern int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
  				   struct gnttab_map_grant_ref *kmap_ops,
  				   struct page **pages, unsigned int count);
  extern int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
  				     struct gnttab_unmap_grant_ref *kunmap_ops,
  				     struct page **pages, unsigned int count);
  
  /*
   * Helper functions to write or read unsigned long values to/from
   * memory, when the access may fault.
   */
  static inline int xen_safe_write_ulong(unsigned long *addr, unsigned long val)
  {
  	return __put_user(val, (unsigned long __user *)addr);
  }
  
  static inline int xen_safe_read_ulong(unsigned long *addr, unsigned long *val)
  {
  	return __get_user(*val, (unsigned long __user *)addr);
  }
  
  /*
   * When to use pfn_to_mfn(), __pfn_to_mfn() or get_phys_to_machine():
   * - pfn_to_mfn() returns either INVALID_P2M_ENTRY or the mfn. No indicator
   *   bits (identity or foreign) are set.
   * - __pfn_to_mfn() returns the found entry of the p2m table. A possibly set
   *   identity or foreign indicator will be still set. __pfn_to_mfn() is
   *   encapsulating get_phys_to_machine() which is called in special cases only.
   * - get_phys_to_machine() is to be called by __pfn_to_mfn() only in special
   *   cases needing an extended handling.
   */
  static inline unsigned long __pfn_to_mfn(unsigned long pfn)
  {
  	unsigned long mfn;
  
  	if (pfn < xen_p2m_size)
  		mfn = xen_p2m_addr[pfn];
  	else if (unlikely(pfn < xen_max_p2m_pfn))
  		return get_phys_to_machine(pfn);
  	else
  		return IDENTITY_FRAME(pfn);
  
  	if (unlikely(mfn == INVALID_P2M_ENTRY))
  		return get_phys_to_machine(pfn);
  
  	return mfn;
  }
  
  static inline unsigned long pfn_to_mfn(unsigned long pfn)
  {
  	unsigned long mfn;
  
  	if (xen_feature(XENFEAT_auto_translated_physmap))
  		return pfn;
  
  	mfn = __pfn_to_mfn(pfn);
  
  	if (mfn != INVALID_P2M_ENTRY)
  		mfn &= ~(FOREIGN_FRAME_BIT | IDENTITY_FRAME_BIT);
  
  	return mfn;
  }
  
  static inline int phys_to_machine_mapping_valid(unsigned long pfn)
  {
  	if (xen_feature(XENFEAT_auto_translated_physmap))
  		return 1;
  
  	return __pfn_to_mfn(pfn) != INVALID_P2M_ENTRY;
  }
  
  static inline unsigned long mfn_to_pfn_no_overrides(unsigned long mfn)
  {
  	unsigned long pfn;
  	int ret;
  
  	if (xen_feature(XENFEAT_auto_translated_physmap))
  		return mfn;
  
  	if (unlikely(mfn >= machine_to_phys_nr))
  		return ~0;
  
  	/*
  	 * The array access can fail (e.g., device space beyond end of RAM).
  	 * In such cases it doesn't matter what we return (we return garbage),
  	 * but we must handle the fault without crashing!
  	 */
  	ret = xen_safe_read_ulong(&machine_to_phys_mapping[mfn], &pfn);
  	if (ret < 0)
  		return ~0;
  
  	return pfn;
  }
  
  static inline unsigned long mfn_to_pfn(unsigned long mfn)
  {
  	unsigned long pfn;
  
  	if (xen_feature(XENFEAT_auto_translated_physmap))
  		return mfn;
  
  	pfn = mfn_to_pfn_no_overrides(mfn);
  	if (__pfn_to_mfn(pfn) != mfn)
  		pfn = ~0;
  
  	/*
  	 * pfn is ~0 if there are no entries in the m2p for mfn or the
  	 * entry doesn't map back to the mfn.
  	 */
  	if (pfn == ~0 && __pfn_to_mfn(mfn) == IDENTITY_FRAME(mfn))
  		pfn = mfn;
  
  	return pfn;
  }
  
  static inline xmaddr_t phys_to_machine(xpaddr_t phys)
  {
  	unsigned offset = phys.paddr & ~PAGE_MASK;
  	return XMADDR(PFN_PHYS(pfn_to_mfn(PFN_DOWN(phys.paddr))) | offset);
  }
  
  static inline xpaddr_t machine_to_phys(xmaddr_t machine)
  {
  	unsigned offset = machine.maddr & ~PAGE_MASK;
  	return XPADDR(PFN_PHYS(mfn_to_pfn(PFN_DOWN(machine.maddr))) | offset);
  }
  
  /*
   * We detect special mappings in one of two ways:
   *  1. If the MFN is an I/O page then Xen will set the m2p entry
   *     to be outside our maximum possible pseudophys range.
   *  2. If the MFN belongs to a different domain then we will certainly
   *     not have MFN in our p2m table. Conversely, if the page is ours,
   *     then we'll have p2m(m2p(MFN))==MFN.
   * If we detect a special mapping then it doesn't have a 'struct page'.
   * We force !pfn_valid() by returning an out-of-range pointer.
   *
   * NB. These checks require that, for any MFN that is not in our reservation,
   * there is no PFN such that p2m(PFN) == MFN. Otherwise we can get confused if
   * we are foreign-mapping the MFN, and the other domain as m2p(MFN) == PFN.
   * Yikes! Various places must poke in INVALID_P2M_ENTRY for safety.
   *
   * NB2. When deliberately mapping foreign pages into the p2m table, you *must*
   *      use FOREIGN_FRAME(). This will cause pte_pfn() to choke on it, as we
   *      require. In all the cases we care about, the FOREIGN_FRAME bit is
   *      masked (e.g., pfn_to_mfn()) so behaviour there is correct.
   */
  static inline unsigned long mfn_to_local_pfn(unsigned long mfn)
  {
  	unsigned long pfn;
  
  	if (xen_feature(XENFEAT_auto_translated_physmap))
  		return mfn;
  
  	pfn = mfn_to_pfn(mfn);
  	if (__pfn_to_mfn(pfn) != mfn)
  		return -1; /* force !pfn_valid() */
  	return pfn;
  }
  
  /* VIRT <-> MACHINE conversion */
  #define virt_to_machine(v)	(phys_to_machine(XPADDR(__pa(v))))
  #define virt_to_pfn(v)          (PFN_DOWN(__pa(v)))
  #define virt_to_mfn(v)		(pfn_to_mfn(virt_to_pfn(v)))
  #define mfn_to_virt(m)		(__va(mfn_to_pfn(m) << PAGE_SHIFT))
  
  static inline unsigned long pte_mfn(pte_t pte)
  {
  	return (pte.pte & PTE_PFN_MASK) >> PAGE_SHIFT;
  }
  
  static inline pte_t mfn_pte(unsigned long page_nr, pgprot_t pgprot)
  {
  	pte_t pte;
  
  	pte.pte = ((phys_addr_t)page_nr << PAGE_SHIFT) |
  			massage_pgprot(pgprot);
  
  	return pte;
  }
  
  static inline pteval_t pte_val_ma(pte_t pte)
  {
  	return pte.pte;
  }
  
  static inline pte_t __pte_ma(pteval_t x)
  {
  	return (pte_t) { .pte = x };
  }
  
  #define pmd_val_ma(v) ((v).pmd)
  #ifdef __PAGETABLE_PUD_FOLDED
  #define pud_val_ma(v) ((v).pgd.pgd)
  #else
  #define pud_val_ma(v) ((v).pud)
  #endif
  #define __pmd_ma(x)	((pmd_t) { (x) } )
  
  #define pgd_val_ma(x)	((x).pgd)
  
  void xen_set_domain_pte(pte_t *ptep, pte_t pteval, unsigned domid);
  
  xmaddr_t arbitrary_virt_to_machine(void *address);
  unsigned long arbitrary_virt_to_mfn(void *vaddr);
  void make_lowmem_page_readonly(void *vaddr);
  void make_lowmem_page_readwrite(void *vaddr);
  
  #define xen_remap(cookie, size) ioremap((cookie), (size));
  #define xen_unmap(cookie) iounmap((cookie))
  
  static inline bool xen_arch_need_swiotlb(struct device *dev,
  					 unsigned long pfn,
  					 unsigned long mfn)
  {
  	return false;
  }
  
  #endif /* _ASM_X86_XEN_PAGE_H */
  