xref: /linux/arch/x86/xen/mmu_pv.c (revision 74ce1896c6c65b2f8cccbf59162d542988835835)

/*
 * Xen mmu operations
 *
 * This file contains the various mmu fetch and update operations.
 * The most important job they must perform is the mapping between the
 * domain's pfn and the overall machine mfns.
 *
 * Xen allows guests to directly update the pagetable, in a controlled
 * fashion.  In other words, the guest modifies the same pagetable
 * that the CPU actually uses, which eliminates the overhead of having
 * a separate shadow pagetable.
 *
 * In order to allow this, it falls on the guest domain to map its
 * notion of a "physical" pfn - which is just a domain-local linear
 * address - into a real "machine address" which the CPU's MMU can
 * use.
 *
 * A pgd_t/pmd_t/pte_t will typically contain an mfn, and so can be
 * inserted directly into the pagetable.  When creating a new
 * pte/pmd/pgd, it converts the passed pfn into an mfn.  Conversely,
 * when reading the content back with __(pgd|pmd|pte)_val, it converts
 * the mfn back into a pfn.
 *
 * The other constraint is that all pages which make up a pagetable
 * must be mapped read-only in the guest.  This prevents uncontrolled
 * guest updates to the pagetable.  Xen strictly enforces this, and
 * will disallow any pagetable update which will end up mapping a
 * pagetable page RW, and will disallow using any writable page as a
 * pagetable.
 *
 * Naively, when loading %cr3 with the base of a new pagetable, Xen
 * would need to validate the whole pagetable before going on.
 * Naturally, this is quite slow.  The solution is to "pin" a
 * pagetable, which enforces all the constraints on the pagetable even
 * when it is not actively in use.  This menas that Xen can be assured
 * that it is still valid when you do load it into %cr3, and doesn't
 * need to revalidate it.
 *
 * Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
 */
#include <linux/sched/mm.h>
#include <linux/highmem.h>
#include <linux/debugfs.h>
#include <linux/bug.h>
#include <linux/vmalloc.h>
#include <linux/export.h>
#include <linux/init.h>
#include <linux/gfp.h>
#include <linux/memblock.h>
#include <linux/seq_file.h>
#include <linux/crash_dump.h>
#ifdef CONFIG_KEXEC_CORE
#include <linux/kexec.h>
#endif

#include <trace/events/xen.h>

#include <asm/pgtable.h>
#include <asm/tlbflush.h>
#include <asm/fixmap.h>
#include <asm/mmu_context.h>
#include <asm/setup.h>
#include <asm/paravirt.h>
#include <asm/e820/api.h>
#include <asm/linkage.h>
#include <asm/page.h>
#include <asm/init.h>
#include <asm/pat.h>
#include <asm/smp.h>

#include <asm/xen/hypercall.h>
#include <asm/xen/hypervisor.h>

#include <xen/xen.h>
#include <xen/page.h>
#include <xen/interface/xen.h>
#include <xen/interface/hvm/hvm_op.h>
#include <xen/interface/version.h>
#include <xen/interface/memory.h>
#include <xen/hvc-console.h>

#include "multicalls.h"
#include "mmu.h"
#include "debugfs.h"

#ifdef CONFIG_X86_32
/*
 * Identity map, in addition to plain kernel map.  This needs to be
 * large enough to allocate page table pages to allocate the rest.
 * Each page can map 2MB.
 */
#define LEVEL1_IDENT_ENTRIES	(PTRS_PER_PTE * 4)
static RESERVE_BRK_ARRAY(pte_t, level1_ident_pgt, LEVEL1_IDENT_ENTRIES);
#endif
#ifdef CONFIG_X86_64
/* l3 pud for userspace vsyscall mapping */
static pud_t level3_user_vsyscall[PTRS_PER_PUD] __page_aligned_bss;
#endif /* CONFIG_X86_64 */

/*
 * Note about cr3 (pagetable base) values:
 *
 * xen_cr3 contains the current logical cr3 value; it contains the
 * last set cr3.  This may not be the current effective cr3, because
 * its update may be being lazily deferred.  However, a vcpu looking
 * at its own cr3 can use this value knowing that it everything will
 * be self-consistent.
 *
 * xen_current_cr3 contains the actual vcpu cr3; it is set once the
 * hypercall to set the vcpu cr3 is complete (so it may be a little
 * out of date, but it will never be set early).  If one vcpu is
 * looking at another vcpu's cr3 value, it should use this variable.
 */
DEFINE_PER_CPU(unsigned long, xen_cr3);	 /* cr3 stored as physaddr */
DEFINE_PER_CPU(unsigned long, xen_current_cr3);	 /* actual vcpu cr3 */

static phys_addr_t xen_pt_base, xen_pt_size __initdata;

/*
 * Just beyond the highest usermode address.  STACK_TOP_MAX has a
 * redzone above it, so round it up to a PGD boundary.
 */
#define USER_LIMIT	((STACK_TOP_MAX + PGDIR_SIZE - 1) & PGDIR_MASK)

void make_lowmem_page_readonly(void *vaddr)
{
	pte_t *pte, ptev;
	unsigned long address = (unsigned long)vaddr;
	unsigned int level;

	pte = lookup_address(address, &level);
	if (pte == NULL)
		return;		/* vaddr missing */

	ptev = pte_wrprotect(*pte);

	if (HYPERVISOR_update_va_mapping(address, ptev, 0))
		BUG();
}

void make_lowmem_page_readwrite(void *vaddr)
{
	pte_t *pte, ptev;
	unsigned long address = (unsigned long)vaddr;
	unsigned int level;

	pte = lookup_address(address, &level);
	if (pte == NULL)
		return;		/* vaddr missing */

	ptev = pte_mkwrite(*pte);

	if (HYPERVISOR_update_va_mapping(address, ptev, 0))
		BUG();
}


static bool xen_page_pinned(void *ptr)
{
	struct page *page = virt_to_page(ptr);

	return PagePinned(page);
}

static void xen_extend_mmu_update(const struct mmu_update *update)
{
	struct multicall_space mcs;
	struct mmu_update *u;

	mcs = xen_mc_extend_args(__HYPERVISOR_mmu_update, sizeof(*u));

	if (mcs.mc != NULL) {
		mcs.mc->args[1]++;
	} else {
		mcs = __xen_mc_entry(sizeof(*u));
		MULTI_mmu_update(mcs.mc, mcs.args, 1, NULL, DOMID_SELF);
	}

	u = mcs.args;
	*u = *update;
}

static void xen_extend_mmuext_op(const struct mmuext_op *op)
{
	struct multicall_space mcs;
	struct mmuext_op *u;

	mcs = xen_mc_extend_args(__HYPERVISOR_mmuext_op, sizeof(*u));

	if (mcs.mc != NULL) {
		mcs.mc->args[1]++;
	} else {
		mcs = __xen_mc_entry(sizeof(*u));
		MULTI_mmuext_op(mcs.mc, mcs.args, 1, NULL, DOMID_SELF);
	}

	u = mcs.args;
	*u = *op;
}

static void xen_set_pmd_hyper(pmd_t *ptr, pmd_t val)
{
	struct mmu_update u;

	preempt_disable();

	xen_mc_batch();

	/* ptr may be ioremapped for 64-bit pagetable setup */
	u.ptr = arbitrary_virt_to_machine(ptr).maddr;
	u.val = pmd_val_ma(val);
	xen_extend_mmu_update(&u);

	xen_mc_issue(PARAVIRT_LAZY_MMU);

	preempt_enable();
}

static void xen_set_pmd(pmd_t *ptr, pmd_t val)
{
	trace_xen_mmu_set_pmd(ptr, val);

	/* If page is not pinned, we can just update the entry
	   directly */
	if (!xen_page_pinned(ptr)) {
		*ptr = val;
		return;
	}

	xen_set_pmd_hyper(ptr, val);
}

/*
 * Associate a virtual page frame with a given physical page frame
 * and protection flags for that frame.
 */
void set_pte_mfn(unsigned long vaddr, unsigned long mfn, pgprot_t flags)
{
	set_pte_vaddr(vaddr, mfn_pte(mfn, flags));
}

static bool xen_batched_set_pte(pte_t *ptep, pte_t pteval)
{
	struct mmu_update u;

	if (paravirt_get_lazy_mode() != PARAVIRT_LAZY_MMU)
		return false;

	xen_mc_batch();

	u.ptr = virt_to_machine(ptep).maddr | MMU_NORMAL_PT_UPDATE;
	u.val = pte_val_ma(pteval);
	xen_extend_mmu_update(&u);

	xen_mc_issue(PARAVIRT_LAZY_MMU);

	return true;
}

static inline void __xen_set_pte(pte_t *ptep, pte_t pteval)
{
	if (!xen_batched_set_pte(ptep, pteval)) {
		/*
		 * Could call native_set_pte() here and trap and
		 * emulate the PTE write but with 32-bit guests this
		 * needs two traps (one for each of the two 32-bit
		 * words in the PTE) so do one hypercall directly
		 * instead.
		 */
		struct mmu_update u;

		u.ptr = virt_to_machine(ptep).maddr | MMU_NORMAL_PT_UPDATE;
		u.val = pte_val_ma(pteval);
		HYPERVISOR_mmu_update(&u, 1, NULL, DOMID_SELF);
	}
}

static void xen_set_pte(pte_t *ptep, pte_t pteval)
{
	trace_xen_mmu_set_pte(ptep, pteval);
	__xen_set_pte(ptep, pteval);
}

static void xen_set_pte_at(struct mm_struct *mm, unsigned long addr,
		    pte_t *ptep, pte_t pteval)
{
	trace_xen_mmu_set_pte_at(mm, addr, ptep, pteval);
	__xen_set_pte(ptep, pteval);
}

pte_t xen_ptep_modify_prot_start(struct mm_struct *mm,
				 unsigned long addr, pte_t *ptep)
{
	/* Just return the pte as-is.  We preserve the bits on commit */
	trace_xen_mmu_ptep_modify_prot_start(mm, addr, ptep, *ptep);
	return *ptep;
}

void xen_ptep_modify_prot_commit(struct mm_struct *mm, unsigned long addr,
				 pte_t *ptep, pte_t pte)
{
	struct mmu_update u;

	trace_xen_mmu_ptep_modify_prot_commit(mm, addr, ptep, pte);
	xen_mc_batch();

	u.ptr = virt_to_machine(ptep).maddr | MMU_PT_UPDATE_PRESERVE_AD;
	u.val = pte_val_ma(pte);
	xen_extend_mmu_update(&u);

	xen_mc_issue(PARAVIRT_LAZY_MMU);
}

/* Assume pteval_t is equivalent to all the other *val_t types. */
static pteval_t pte_mfn_to_pfn(pteval_t val)
{
	if (val & _PAGE_PRESENT) {
		unsigned long mfn = (val & PTE_PFN_MASK) >> PAGE_SHIFT;
		unsigned long pfn = mfn_to_pfn(mfn);

		pteval_t flags = val & PTE_FLAGS_MASK;
		if (unlikely(pfn == ~0))
			val = flags & ~_PAGE_PRESENT;
		else
			val = ((pteval_t)pfn << PAGE_SHIFT) | flags;
	}

	return val;
}

static pteval_t pte_pfn_to_mfn(pteval_t val)
{
	if (val & _PAGE_PRESENT) {
		unsigned long pfn = (val & PTE_PFN_MASK) >> PAGE_SHIFT;
		pteval_t flags = val & PTE_FLAGS_MASK;
		unsigned long mfn;

		mfn = __pfn_to_mfn(pfn);

		/*
		 * If there's no mfn for the pfn, then just create an
		 * empty non-present pte.  Unfortunately this loses
		 * information about the original pfn, so
		 * pte_mfn_to_pfn is asymmetric.
		 */
		if (unlikely(mfn == INVALID_P2M_ENTRY)) {
			mfn = 0;
			flags = 0;
		} else
			mfn &= ~(FOREIGN_FRAME_BIT | IDENTITY_FRAME_BIT);
		val = ((pteval_t)mfn << PAGE_SHIFT) | flags;
	}

	return val;
}

__visible pteval_t xen_pte_val(pte_t pte)
{
	pteval_t pteval = pte.pte;

	return pte_mfn_to_pfn(pteval);
}
PV_CALLEE_SAVE_REGS_THUNK(xen_pte_val);

__visible pgdval_t xen_pgd_val(pgd_t pgd)
{
	return pte_mfn_to_pfn(pgd.pgd);
}
PV_CALLEE_SAVE_REGS_THUNK(xen_pgd_val);

__visible pte_t xen_make_pte(pteval_t pte)
{
	pte = pte_pfn_to_mfn(pte);

	return native_make_pte(pte);
}
PV_CALLEE_SAVE_REGS_THUNK(xen_make_pte);

__visible pgd_t xen_make_pgd(pgdval_t pgd)
{
	pgd = pte_pfn_to_mfn(pgd);
	return native_make_pgd(pgd);
}
PV_CALLEE_SAVE_REGS_THUNK(xen_make_pgd);

__visible pmdval_t xen_pmd_val(pmd_t pmd)
{
	return pte_mfn_to_pfn(pmd.pmd);
}
PV_CALLEE_SAVE_REGS_THUNK(xen_pmd_val);

static void xen_set_pud_hyper(pud_t *ptr, pud_t val)
{
	struct mmu_update u;

	preempt_disable();

	xen_mc_batch();

	/* ptr may be ioremapped for 64-bit pagetable setup */
	u.ptr = arbitrary_virt_to_machine(ptr).maddr;
	u.val = pud_val_ma(val);
	xen_extend_mmu_update(&u);

	xen_mc_issue(PARAVIRT_LAZY_MMU);

	preempt_enable();
}

static void xen_set_pud(pud_t *ptr, pud_t val)
{
	trace_xen_mmu_set_pud(ptr, val);

	/* If page is not pinned, we can just update the entry
	   directly */
	if (!xen_page_pinned(ptr)) {
		*ptr = val;
		return;
	}

	xen_set_pud_hyper(ptr, val);
}

#ifdef CONFIG_X86_PAE
static void xen_set_pte_atomic(pte_t *ptep, pte_t pte)
{
	trace_xen_mmu_set_pte_atomic(ptep, pte);
	set_64bit((u64 *)ptep, native_pte_val(pte));
}

static void xen_pte_clear(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
{
	trace_xen_mmu_pte_clear(mm, addr, ptep);
	if (!xen_batched_set_pte(ptep, native_make_pte(0)))
		native_pte_clear(mm, addr, ptep);
}

static void xen_pmd_clear(pmd_t *pmdp)
{
	trace_xen_mmu_pmd_clear(pmdp);
	set_pmd(pmdp, __pmd(0));
}
#endif	/* CONFIG_X86_PAE */

__visible pmd_t xen_make_pmd(pmdval_t pmd)
{
	pmd = pte_pfn_to_mfn(pmd);
	return native_make_pmd(pmd);
}
PV_CALLEE_SAVE_REGS_THUNK(xen_make_pmd);

#if CONFIG_PGTABLE_LEVELS == 4
__visible pudval_t xen_pud_val(pud_t pud)
{
	return pte_mfn_to_pfn(pud.pud);
}
PV_CALLEE_SAVE_REGS_THUNK(xen_pud_val);

__visible pud_t xen_make_pud(pudval_t pud)
{
	pud = pte_pfn_to_mfn(pud);

	return native_make_pud(pud);
}
PV_CALLEE_SAVE_REGS_THUNK(xen_make_pud);

static pgd_t *xen_get_user_pgd(pgd_t *pgd)
{
	pgd_t *pgd_page = (pgd_t *)(((unsigned long)pgd) & PAGE_MASK);
	unsigned offset = pgd - pgd_page;
	pgd_t *user_ptr = NULL;

	if (offset < pgd_index(USER_LIMIT)) {
		struct page *page = virt_to_page(pgd_page);
		user_ptr = (pgd_t *)page->private;
		if (user_ptr)
			user_ptr += offset;
	}

	return user_ptr;
}

static void __xen_set_p4d_hyper(p4d_t *ptr, p4d_t val)
{
	struct mmu_update u;

	u.ptr = virt_to_machine(ptr).maddr;
	u.val = p4d_val_ma(val);
	xen_extend_mmu_update(&u);
}

/*
 * Raw hypercall-based set_p4d, intended for in early boot before
 * there's a page structure.  This implies:
 *  1. The only existing pagetable is the kernel's
 *  2. It is always pinned
 *  3. It has no user pagetable attached to it
 */
static void __init xen_set_p4d_hyper(p4d_t *ptr, p4d_t val)
{
	preempt_disable();

	xen_mc_batch();

	__xen_set_p4d_hyper(ptr, val);

	xen_mc_issue(PARAVIRT_LAZY_MMU);

	preempt_enable();
}

static void xen_set_p4d(p4d_t *ptr, p4d_t val)
{
	pgd_t *user_ptr = xen_get_user_pgd((pgd_t *)ptr);
	pgd_t pgd_val;

	trace_xen_mmu_set_p4d(ptr, (p4d_t *)user_ptr, val);

	/* If page is not pinned, we can just update the entry
	   directly */
	if (!xen_page_pinned(ptr)) {
		*ptr = val;
		if (user_ptr) {
			WARN_ON(xen_page_pinned(user_ptr));
			pgd_val.pgd = p4d_val_ma(val);
			*user_ptr = pgd_val;
		}
		return;
	}

	/* If it's pinned, then we can at least batch the kernel and
	   user updates together. */
	xen_mc_batch();

	__xen_set_p4d_hyper(ptr, val);
	if (user_ptr)
		__xen_set_p4d_hyper((p4d_t *)user_ptr, val);

	xen_mc_issue(PARAVIRT_LAZY_MMU);
}
#endif	/* CONFIG_PGTABLE_LEVELS == 4 */

static int xen_pmd_walk(struct mm_struct *mm, pmd_t *pmd,
		int (*func)(struct mm_struct *mm, struct page *, enum pt_level),
		bool last, unsigned long limit)
{
	int i, nr, flush = 0;

	nr = last ? pmd_index(limit) + 1 : PTRS_PER_PMD;
	for (i = 0; i < nr; i++) {
		if (!pmd_none(pmd[i]))
			flush |= (*func)(mm, pmd_page(pmd[i]), PT_PTE);
	}
	return flush;
}

static int xen_pud_walk(struct mm_struct *mm, pud_t *pud,
		int (*func)(struct mm_struct *mm, struct page *, enum pt_level),
		bool last, unsigned long limit)
{
	int i, nr, flush = 0;

	nr = last ? pud_index(limit) + 1 : PTRS_PER_PUD;
	for (i = 0; i < nr; i++) {
		pmd_t *pmd;

		if (pud_none(pud[i]))
			continue;

		pmd = pmd_offset(&pud[i], 0);
		if (PTRS_PER_PMD > 1)
			flush |= (*func)(mm, virt_to_page(pmd), PT_PMD);
		flush |= xen_pmd_walk(mm, pmd, func,
				last && i == nr - 1, limit);
	}
	return flush;
}

static int xen_p4d_walk(struct mm_struct *mm, p4d_t *p4d,
		int (*func)(struct mm_struct *mm, struct page *, enum pt_level),
		bool last, unsigned long limit)
{
	int i, nr, flush = 0;

	nr = last ? p4d_index(limit) + 1 : PTRS_PER_P4D;
	for (i = 0; i < nr; i++) {
		pud_t *pud;

		if (p4d_none(p4d[i]))
			continue;

		pud = pud_offset(&p4d[i], 0);
		if (PTRS_PER_PUD > 1)
			flush |= (*func)(mm, virt_to_page(pud), PT_PUD);
		flush |= xen_pud_walk(mm, pud, func,
				last && i == nr - 1, limit);
	}
	return flush;
}

/*
 * (Yet another) pagetable walker.  This one is intended for pinning a
 * pagetable.  This means that it walks a pagetable and calls the
 * callback function on each page it finds making up the page table,
 * at every level.  It walks the entire pagetable, but it only bothers
 * pinning pte pages which are below limit.  In the normal case this
 * will be STACK_TOP_MAX, but at boot we need to pin up to
 * FIXADDR_TOP.
 *
 * For 32-bit the important bit is that we don't pin beyond there,
 * because then we start getting into Xen's ptes.
 *
 * For 64-bit, we must skip the Xen hole in the middle of the address
 * space, just after the big x86-64 virtual hole.
 */
static int __xen_pgd_walk(struct mm_struct *mm, pgd_t *pgd,
			  int (*func)(struct mm_struct *mm, struct page *,
				      enum pt_level),
			  unsigned long limit)
{
	int i, nr, flush = 0;
	unsigned hole_low, hole_high;

	/* The limit is the last byte to be touched */
	limit--;
	BUG_ON(limit >= FIXADDR_TOP);

	/*
	 * 64-bit has a great big hole in the middle of the address
	 * space, which contains the Xen mappings.  On 32-bit these
	 * will end up making a zero-sized hole and so is a no-op.
	 */
	hole_low = pgd_index(USER_LIMIT);
	hole_high = pgd_index(PAGE_OFFSET);

	nr = pgd_index(limit) + 1;
	for (i = 0; i < nr; i++) {
		p4d_t *p4d;

		if (i >= hole_low && i < hole_high)
			continue;

		if (pgd_none(pgd[i]))
			continue;

		p4d = p4d_offset(&pgd[i], 0);
		if (PTRS_PER_P4D > 1)
			flush |= (*func)(mm, virt_to_page(p4d), PT_P4D);
		flush |= xen_p4d_walk(mm, p4d, func, i == nr - 1, limit);
	}

	/* Do the top level last, so that the callbacks can use it as
	   a cue to do final things like tlb flushes. */
	flush |= (*func)(mm, virt_to_page(pgd), PT_PGD);

	return flush;
}

static int xen_pgd_walk(struct mm_struct *mm,
			int (*func)(struct mm_struct *mm, struct page *,
				    enum pt_level),
			unsigned long limit)
{
	return __xen_pgd_walk(mm, mm->pgd, func, limit);
}

/* If we're using split pte locks, then take the page's lock and
   return a pointer to it.  Otherwise return NULL. */
static spinlock_t *xen_pte_lock(struct page *page, struct mm_struct *mm)
{
	spinlock_t *ptl = NULL;

#if USE_SPLIT_PTE_PTLOCKS
	ptl = ptlock_ptr(page);
	spin_lock_nest_lock(ptl, &mm->page_table_lock);
#endif

	return ptl;
}

static void xen_pte_unlock(void *v)
{
	spinlock_t *ptl = v;
	spin_unlock(ptl);
}

static void xen_do_pin(unsigned level, unsigned long pfn)
{
	struct mmuext_op op;

	op.cmd = level;
	op.arg1.mfn = pfn_to_mfn(pfn);

	xen_extend_mmuext_op(&op);
}

static int xen_pin_page(struct mm_struct *mm, struct page *page,
			enum pt_level level)
{
	unsigned pgfl = TestSetPagePinned(page);
	int flush;

	if (pgfl)
		flush = 0;		/* already pinned */
	else if (PageHighMem(page))
		/* kmaps need flushing if we found an unpinned
		   highpage */
		flush = 1;
	else {
		void *pt = lowmem_page_address(page);
		unsigned long pfn = page_to_pfn(page);
		struct multicall_space mcs = __xen_mc_entry(0);
		spinlock_t *ptl;

		flush = 0;

		/*
		 * We need to hold the pagetable lock between the time
		 * we make the pagetable RO and when we actually pin
		 * it.  If we don't, then other users may come in and
		 * attempt to update the pagetable by writing it,
		 * which will fail because the memory is RO but not
		 * pinned, so Xen won't do the trap'n'emulate.
		 *
		 * If we're using split pte locks, we can't hold the
		 * entire pagetable's worth of locks during the
		 * traverse, because we may wrap the preempt count (8
		 * bits).  The solution is to mark RO and pin each PTE
		 * page while holding the lock.  This means the number
		 * of locks we end up holding is never more than a
		 * batch size (~32 entries, at present).
		 *
		 * If we're not using split pte locks, we needn't pin
		 * the PTE pages independently, because we're
		 * protected by the overall pagetable lock.
		 */
		ptl = NULL;
		if (level == PT_PTE)
			ptl = xen_pte_lock(page, mm);

		MULTI_update_va_mapping(mcs.mc, (unsigned long)pt,
					pfn_pte(pfn, PAGE_KERNEL_RO),
					level == PT_PGD ? UVMF_TLB_FLUSH : 0);

		if (ptl) {
			xen_do_pin(MMUEXT_PIN_L1_TABLE, pfn);

			/* Queue a deferred unlock for when this batch
			   is completed. */
			xen_mc_callback(xen_pte_unlock, ptl);
		}
	}

	return flush;
}

/* This is called just after a mm has been created, but it has not
   been used yet.  We need to make sure that its pagetable is all
   read-only, and can be pinned. */
static void __xen_pgd_pin(struct mm_struct *mm, pgd_t *pgd)
{
	trace_xen_mmu_pgd_pin(mm, pgd);

	xen_mc_batch();

	if (__xen_pgd_walk(mm, pgd, xen_pin_page, USER_LIMIT)) {
		/* re-enable interrupts for flushing */
		xen_mc_issue(0);

		kmap_flush_unused();

		xen_mc_batch();
	}

#ifdef CONFIG_X86_64
	{
		pgd_t *user_pgd = xen_get_user_pgd(pgd);

		xen_do_pin(MMUEXT_PIN_L4_TABLE, PFN_DOWN(__pa(pgd)));

		if (user_pgd) {
			xen_pin_page(mm, virt_to_page(user_pgd), PT_PGD);
			xen_do_pin(MMUEXT_PIN_L4_TABLE,
				   PFN_DOWN(__pa(user_pgd)));
		}
	}
#else /* CONFIG_X86_32 */
#ifdef CONFIG_X86_PAE
	/* Need to make sure unshared kernel PMD is pinnable */
	xen_pin_page(mm, pgd_page(pgd[pgd_index(TASK_SIZE)]),
		     PT_PMD);
#endif
	xen_do_pin(MMUEXT_PIN_L3_TABLE, PFN_DOWN(__pa(pgd)));
#endif /* CONFIG_X86_64 */
	xen_mc_issue(0);
}

static void xen_pgd_pin(struct mm_struct *mm)
{
	__xen_pgd_pin(mm, mm->pgd);
}

/*
 * On save, we need to pin all pagetables to make sure they get their
 * mfns turned into pfns.  Search the list for any unpinned pgds and pin
 * them (unpinned pgds are not currently in use, probably because the
 * process is under construction or destruction).
 *
 * Expected to be called in stop_machine() ("equivalent to taking
 * every spinlock in the system"), so the locking doesn't really
 * matter all that much.
 */
void xen_mm_pin_all(void)
{
	struct page *page;

	spin_lock(&pgd_lock);

	list_for_each_entry(page, &pgd_list, lru) {
		if (!PagePinned(page)) {
			__xen_pgd_pin(&init_mm, (pgd_t *)page_address(page));
			SetPageSavePinned(page);
		}
	}

	spin_unlock(&pgd_lock);
}

/*
 * The init_mm pagetable is really pinned as soon as its created, but
 * that's before we have page structures to store the bits.  So do all
 * the book-keeping now.
 */
static int __init xen_mark_pinned(struct mm_struct *mm, struct page *page,
				  enum pt_level level)
{
	SetPagePinned(page);
	return 0;
}

static void __init xen_mark_init_mm_pinned(void)
{
	xen_pgd_walk(&init_mm, xen_mark_pinned, FIXADDR_TOP);
}

static int xen_unpin_page(struct mm_struct *mm, struct page *page,
			  enum pt_level level)
{
	unsigned pgfl = TestClearPagePinned(page);

	if (pgfl && !PageHighMem(page)) {
		void *pt = lowmem_page_address(page);
		unsigned long pfn = page_to_pfn(page);
		spinlock_t *ptl = NULL;
		struct multicall_space mcs;

		/*
		 * Do the converse to pin_page.  If we're using split
		 * pte locks, we must be holding the lock for while
		 * the pte page is unpinned but still RO to prevent
		 * concurrent updates from seeing it in this
		 * partially-pinned state.
		 */
		if (level == PT_PTE) {
			ptl = xen_pte_lock(page, mm);

			if (ptl)
				xen_do_pin(MMUEXT_UNPIN_TABLE, pfn);
		}

		mcs = __xen_mc_entry(0);

		MULTI_update_va_mapping(mcs.mc, (unsigned long)pt,
					pfn_pte(pfn, PAGE_KERNEL),
					level == PT_PGD ? UVMF_TLB_FLUSH : 0);

		if (ptl) {
			/* unlock when batch completed */
			xen_mc_callback(xen_pte_unlock, ptl);
		}
	}

	return 0;		/* never need to flush on unpin */
}

/* Release a pagetables pages back as normal RW */
static void __xen_pgd_unpin(struct mm_struct *mm, pgd_t *pgd)
{
	trace_xen_mmu_pgd_unpin(mm, pgd);

	xen_mc_batch();

	xen_do_pin(MMUEXT_UNPIN_TABLE, PFN_DOWN(__pa(pgd)));

#ifdef CONFIG_X86_64
	{
		pgd_t *user_pgd = xen_get_user_pgd(pgd);

		if (user_pgd) {
			xen_do_pin(MMUEXT_UNPIN_TABLE,
				   PFN_DOWN(__pa(user_pgd)));
			xen_unpin_page(mm, virt_to_page(user_pgd), PT_PGD);
		}
	}
#endif

#ifdef CONFIG_X86_PAE
	/* Need to make sure unshared kernel PMD is unpinned */
	xen_unpin_page(mm, pgd_page(pgd[pgd_index(TASK_SIZE)]),
		       PT_PMD);
#endif

	__xen_pgd_walk(mm, pgd, xen_unpin_page, USER_LIMIT);

	xen_mc_issue(0);
}

static void xen_pgd_unpin(struct mm_struct *mm)
{
	__xen_pgd_unpin(mm, mm->pgd);
}

/*
 * On resume, undo any pinning done at save, so that the rest of the
 * kernel doesn't see any unexpected pinned pagetables.
 */
void xen_mm_unpin_all(void)
{
	struct page *page;

	spin_lock(&pgd_lock);

	list_for_each_entry(page, &pgd_list, lru) {
		if (PageSavePinned(page)) {
			BUG_ON(!PagePinned(page));
			__xen_pgd_unpin(&init_mm, (pgd_t *)page_address(page));
			ClearPageSavePinned(page);
		}
	}

	spin_unlock(&pgd_lock);
}

static void xen_activate_mm(struct mm_struct *prev, struct mm_struct *next)
{
	spin_lock(&next->page_table_lock);
	xen_pgd_pin(next);
	spin_unlock(&next->page_table_lock);
}

static void xen_dup_mmap(struct mm_struct *oldmm, struct mm_struct *mm)
{
	spin_lock(&mm->page_table_lock);
	xen_pgd_pin(mm);
	spin_unlock(&mm->page_table_lock);
}

static void drop_mm_ref_this_cpu(void *info)
{
	struct mm_struct *mm = info;

	if (this_cpu_read(cpu_tlbstate.loaded_mm) == mm)
		leave_mm(smp_processor_id());

	/*
	 * If this cpu still has a stale cr3 reference, then make sure
	 * it has been flushed.
	 */
	if (this_cpu_read(xen_current_cr3) == __pa(mm->pgd))
		xen_mc_flush();
}

#ifdef CONFIG_SMP
/*
 * Another cpu may still have their %cr3 pointing at the pagetable, so
 * we need to repoint it somewhere else before we can unpin it.
 */
static void xen_drop_mm_ref(struct mm_struct *mm)
{
	cpumask_var_t mask;
	unsigned cpu;

	drop_mm_ref_this_cpu(mm);

	/* Get the "official" set of cpus referring to our pagetable. */
	if (!alloc_cpumask_var(&mask, GFP_ATOMIC)) {
		for_each_online_cpu(cpu) {
			if (per_cpu(xen_current_cr3, cpu) != __pa(mm->pgd))
				continue;
			smp_call_function_single(cpu, drop_mm_ref_this_cpu, mm, 1);
		}
		return;
	}

	/*
	 * It's possible that a vcpu may have a stale reference to our
	 * cr3, because its in lazy mode, and it hasn't yet flushed
	 * its set of pending hypercalls yet.  In this case, we can
	 * look at its actual current cr3 value, and force it to flush
	 * if needed.
	 */
	cpumask_clear(mask);
	for_each_online_cpu(cpu) {
		if (per_cpu(xen_current_cr3, cpu) == __pa(mm->pgd))
			cpumask_set_cpu(cpu, mask);
	}

	smp_call_function_many(mask, drop_mm_ref_this_cpu, mm, 1);
	free_cpumask_var(mask);
}
#else
static void xen_drop_mm_ref(struct mm_struct *mm)
{
	drop_mm_ref_this_cpu(mm);
}
#endif

/*
 * While a process runs, Xen pins its pagetables, which means that the
 * hypervisor forces it to be read-only, and it controls all updates
 * to it.  This means that all pagetable updates have to go via the
 * hypervisor, which is moderately expensive.
 *
 * Since we're pulling the pagetable down, we switch to use init_mm,
 * unpin old process pagetable and mark it all read-write, which
 * allows further operations on it to be simple memory accesses.
 *
 * The only subtle point is that another CPU may be still using the
 * pagetable because of lazy tlb flushing.  This means we need need to
 * switch all CPUs off this pagetable before we can unpin it.
 */
static void xen_exit_mmap(struct mm_struct *mm)
{
	get_cpu();		/* make sure we don't move around */
	xen_drop_mm_ref(mm);
	put_cpu();

	spin_lock(&mm->page_table_lock);

	/* pgd may not be pinned in the error exit path of execve */
	if (xen_page_pinned(mm->pgd))
		xen_pgd_unpin(mm);

	spin_unlock(&mm->page_table_lock);
}

static void xen_post_allocator_init(void);

static void __init pin_pagetable_pfn(unsigned cmd, unsigned long pfn)
{
	struct mmuext_op op;

	op.cmd = cmd;
	op.arg1.mfn = pfn_to_mfn(pfn);
	if (HYPERVISOR_mmuext_op(&op, 1, NULL, DOMID_SELF))
		BUG();
}

#ifdef CONFIG_X86_64
static void __init xen_cleanhighmap(unsigned long vaddr,
				    unsigned long vaddr_end)
{
	unsigned long kernel_end = roundup((unsigned long)_brk_end, PMD_SIZE) - 1;
	pmd_t *pmd = level2_kernel_pgt + pmd_index(vaddr);

	/* NOTE: The loop is more greedy than the cleanup_highmap variant.
	 * We include the PMD passed in on _both_ boundaries. */
	for (; vaddr <= vaddr_end && (pmd < (level2_kernel_pgt + PTRS_PER_PMD));
			pmd++, vaddr += PMD_SIZE) {
		if (pmd_none(*pmd))
			continue;
		if (vaddr < (unsigned long) _text || vaddr > kernel_end)
			set_pmd(pmd, __pmd(0));
	}
	/* In case we did something silly, we should crash in this function
	 * instead of somewhere later and be confusing. */
	xen_mc_flush();
}

/*
 * Make a page range writeable and free it.
 */
static void __init xen_free_ro_pages(unsigned long paddr, unsigned long size)
{
	void *vaddr = __va(paddr);
	void *vaddr_end = vaddr + size;

	for (; vaddr < vaddr_end; vaddr += PAGE_SIZE)
		make_lowmem_page_readwrite(vaddr);

	memblock_free(paddr, size);
}

static void __init xen_cleanmfnmap_free_pgtbl(void *pgtbl, bool unpin)
{
	unsigned long pa = __pa(pgtbl) & PHYSICAL_PAGE_MASK;

	if (unpin)
		pin_pagetable_pfn(MMUEXT_UNPIN_TABLE, PFN_DOWN(pa));
	ClearPagePinned(virt_to_page(__va(pa)));
	xen_free_ro_pages(pa, PAGE_SIZE);
}

static void __init xen_cleanmfnmap_pmd(pmd_t *pmd, bool unpin)
{
	unsigned long pa;
	pte_t *pte_tbl;
	int i;

	if (pmd_large(*pmd)) {
		pa = pmd_val(*pmd) & PHYSICAL_PAGE_MASK;
		xen_free_ro_pages(pa, PMD_SIZE);
		return;
	}

	pte_tbl = pte_offset_kernel(pmd, 0);
	for (i = 0; i < PTRS_PER_PTE; i++) {
		if (pte_none(pte_tbl[i]))
			continue;
		pa = pte_pfn(pte_tbl[i]) << PAGE_SHIFT;
		xen_free_ro_pages(pa, PAGE_SIZE);
	}
	set_pmd(pmd, __pmd(0));
	xen_cleanmfnmap_free_pgtbl(pte_tbl, unpin);
}

static void __init xen_cleanmfnmap_pud(pud_t *pud, bool unpin)
{
	unsigned long pa;
	pmd_t *pmd_tbl;
	int i;

	if (pud_large(*pud)) {
		pa = pud_val(*pud) & PHYSICAL_PAGE_MASK;
		xen_free_ro_pages(pa, PUD_SIZE);
		return;
	}

	pmd_tbl = pmd_offset(pud, 0);
	for (i = 0; i < PTRS_PER_PMD; i++) {
		if (pmd_none(pmd_tbl[i]))
			continue;
		xen_cleanmfnmap_pmd(pmd_tbl + i, unpin);
	}
	set_pud(pud, __pud(0));
	xen_cleanmfnmap_free_pgtbl(pmd_tbl, unpin);
}

static void __init xen_cleanmfnmap_p4d(p4d_t *p4d, bool unpin)
{
	unsigned long pa;
	pud_t *pud_tbl;
	int i;

	if (p4d_large(*p4d)) {
		pa = p4d_val(*p4d) & PHYSICAL_PAGE_MASK;
		xen_free_ro_pages(pa, P4D_SIZE);
		return;
	}

	pud_tbl = pud_offset(p4d, 0);
	for (i = 0; i < PTRS_PER_PUD; i++) {
		if (pud_none(pud_tbl[i]))
			continue;
		xen_cleanmfnmap_pud(pud_tbl + i, unpin);
	}
	set_p4d(p4d, __p4d(0));
	xen_cleanmfnmap_free_pgtbl(pud_tbl, unpin);
}

/*
 * Since it is well isolated we can (and since it is perhaps large we should)
 * also free the page tables mapping the initial P->M table.
 */
static void __init xen_cleanmfnmap(unsigned long vaddr)
{
	pgd_t *pgd;
	p4d_t *p4d;
	unsigned int i;
	bool unpin;

	unpin = (vaddr == 2 * PGDIR_SIZE);
	vaddr &= PMD_MASK;
	pgd = pgd_offset_k(vaddr);
	p4d = p4d_offset(pgd, 0);
	for (i = 0; i < PTRS_PER_P4D; i++) {
		if (p4d_none(p4d[i]))
			continue;
		xen_cleanmfnmap_p4d(p4d + i, unpin);
	}
	if (IS_ENABLED(CONFIG_X86_5LEVEL)) {
		set_pgd(pgd, __pgd(0));
		xen_cleanmfnmap_free_pgtbl(p4d, unpin);
	}
}

static void __init xen_pagetable_p2m_free(void)
{
	unsigned long size;
	unsigned long addr;

	size = PAGE_ALIGN(xen_start_info->nr_pages * sizeof(unsigned long));

	/* No memory or already called. */
	if ((unsigned long)xen_p2m_addr == xen_start_info->mfn_list)
		return;

	/* using __ka address and sticking INVALID_P2M_ENTRY! */
	memset((void *)xen_start_info->mfn_list, 0xff, size);

	addr = xen_start_info->mfn_list;
	/*
	 * We could be in __ka space.
	 * We roundup to the PMD, which means that if anybody at this stage is
	 * using the __ka address of xen_start_info or
	 * xen_start_info->shared_info they are in going to crash. Fortunatly
	 * we have already revectored in xen_setup_kernel_pagetable and in
	 * xen_setup_shared_info.
	 */
	size = roundup(size, PMD_SIZE);

	if (addr >= __START_KERNEL_map) {
		xen_cleanhighmap(addr, addr + size);
		size = PAGE_ALIGN(xen_start_info->nr_pages *
				  sizeof(unsigned long));
		memblock_free(__pa(addr), size);
	} else {
		xen_cleanmfnmap(addr);
	}
}

static void __init xen_pagetable_cleanhighmap(void)
{
	unsigned long size;
	unsigned long addr;

	/* At this stage, cleanup_highmap has already cleaned __ka space
	 * from _brk_limit way up to the max_pfn_mapped (which is the end of
	 * the ramdisk). We continue on, erasing PMD entries that point to page
	 * tables - do note that they are accessible at this stage via __va.
	 * For good measure we also round up to the PMD - which means that if
	 * anybody is using __ka address to the initial boot-stack - and try
	 * to use it - they are going to crash. The xen_start_info has been
	 * taken care of already in xen_setup_kernel_pagetable. */
	addr = xen_start_info->pt_base;
	size = roundup(xen_start_info->nr_pt_frames * PAGE_SIZE, PMD_SIZE);

	xen_cleanhighmap(addr, addr + size);
	xen_start_info->pt_base = (unsigned long)__va(__pa(xen_start_info->pt_base));
#ifdef DEBUG
	/* This is superfluous and is not necessary, but you know what
	 * lets do it. The MODULES_VADDR -> MODULES_END should be clear of
	 * anything at this stage. */
	xen_cleanhighmap(MODULES_VADDR, roundup(MODULES_VADDR, PUD_SIZE) - 1);
#endif
}
#endif

static void __init xen_pagetable_p2m_setup(void)
{
	xen_vmalloc_p2m_tree();

#ifdef CONFIG_X86_64
	xen_pagetable_p2m_free();

	xen_pagetable_cleanhighmap();
#endif
	/* And revector! Bye bye old array */
	xen_start_info->mfn_list = (unsigned long)xen_p2m_addr;
}

static void __init xen_pagetable_init(void)
{
	paging_init();
	xen_post_allocator_init();

	xen_pagetable_p2m_setup();

	/* Allocate and initialize top and mid mfn levels for p2m structure */
	xen_build_mfn_list_list();

	/* Remap memory freed due to conflicts with E820 map */
	xen_remap_memory();

	xen_setup_shared_info();
}
static void xen_write_cr2(unsigned long cr2)
{
	this_cpu_read(xen_vcpu)->arch.cr2 = cr2;
}

static unsigned long xen_read_cr2(void)
{
	return this_cpu_read(xen_vcpu)->arch.cr2;
}

unsigned long xen_read_cr2_direct(void)
{
	return this_cpu_read(xen_vcpu_info.arch.cr2);
}

static void xen_flush_tlb(void)
{
	struct mmuext_op *op;
	struct multicall_space mcs;

	trace_xen_mmu_flush_tlb(0);

	preempt_disable();

	mcs = xen_mc_entry(sizeof(*op));

	op = mcs.args;
	op->cmd = MMUEXT_TLB_FLUSH_LOCAL;
	MULTI_mmuext_op(mcs.mc, op, 1, NULL, DOMID_SELF);

	xen_mc_issue(PARAVIRT_LAZY_MMU);

	preempt_enable();
}

static void xen_flush_tlb_single(unsigned long addr)
{
	struct mmuext_op *op;
	struct multicall_space mcs;

	trace_xen_mmu_flush_tlb_single(addr);

	preempt_disable();

	mcs = xen_mc_entry(sizeof(*op));
	op = mcs.args;
	op->cmd = MMUEXT_INVLPG_LOCAL;
	op->arg1.linear_addr = addr & PAGE_MASK;
	MULTI_mmuext_op(mcs.mc, op, 1, NULL, DOMID_SELF);

	xen_mc_issue(PARAVIRT_LAZY_MMU);

	preempt_enable();
}

static void xen_flush_tlb_others(const struct cpumask *cpus,
				 const struct flush_tlb_info *info)
{
	struct {
		struct mmuext_op op;
#ifdef CONFIG_SMP
		DECLARE_BITMAP(mask, num_processors);
#else
		DECLARE_BITMAP(mask, NR_CPUS);
#endif
	} *args;
	struct multicall_space mcs;

	trace_xen_mmu_flush_tlb_others(cpus, info->mm, info->start, info->end);

	if (cpumask_empty(cpus))
		return;		/* nothing to do */

	mcs = xen_mc_entry(sizeof(*args));
	args = mcs.args;
	args->op.arg2.vcpumask = to_cpumask(args->mask);

	/* Remove us, and any offline CPUS. */
	cpumask_and(to_cpumask(args->mask), cpus, cpu_online_mask);
	cpumask_clear_cpu(smp_processor_id(), to_cpumask(args->mask));

	args->op.cmd = MMUEXT_TLB_FLUSH_MULTI;
	if (info->end != TLB_FLUSH_ALL &&
	    (info->end - info->start) <= PAGE_SIZE) {
		args->op.cmd = MMUEXT_INVLPG_MULTI;
		args->op.arg1.linear_addr = info->start;
	}

	MULTI_mmuext_op(mcs.mc, &args->op, 1, NULL, DOMID_SELF);

	xen_mc_issue(PARAVIRT_LAZY_MMU);
}

static unsigned long xen_read_cr3(void)
{
	return this_cpu_read(xen_cr3);
}

static void set_current_cr3(void *v)
{
	this_cpu_write(xen_current_cr3, (unsigned long)v);
}

static void __xen_write_cr3(bool kernel, unsigned long cr3)
{
	struct mmuext_op op;
	unsigned long mfn;

	trace_xen_mmu_write_cr3(kernel, cr3);

	if (cr3)
		mfn = pfn_to_mfn(PFN_DOWN(cr3));
	else
		mfn = 0;

	WARN_ON(mfn == 0 && kernel);

	op.cmd = kernel ? MMUEXT_NEW_BASEPTR : MMUEXT_NEW_USER_BASEPTR;
	op.arg1.mfn = mfn;

	xen_extend_mmuext_op(&op);

	if (kernel) {
		this_cpu_write(xen_cr3, cr3);

		/* Update xen_current_cr3 once the batch has actually
		   been submitted. */
		xen_mc_callback(set_current_cr3, (void *)cr3);
	}
}
static void xen_write_cr3(unsigned long cr3)
{
	BUG_ON(preemptible());

	xen_mc_batch();  /* disables interrupts */

	/* Update while interrupts are disabled, so its atomic with
	   respect to ipis */
	this_cpu_write(xen_cr3, cr3);

	__xen_write_cr3(true, cr3);

#ifdef CONFIG_X86_64
	{
		pgd_t *user_pgd = xen_get_user_pgd(__va(cr3));
		if (user_pgd)
			__xen_write_cr3(false, __pa(user_pgd));
		else
			__xen_write_cr3(false, 0);
	}
#endif

	xen_mc_issue(PARAVIRT_LAZY_CPU);  /* interrupts restored */
}

#ifdef CONFIG_X86_64
/*
 * At the start of the day - when Xen launches a guest, it has already
 * built pagetables for the guest. We diligently look over them
 * in xen_setup_kernel_pagetable and graft as appropriate them in the
 * init_top_pgt and its friends. Then when we are happy we load
 * the new init_top_pgt - and continue on.
 *
 * The generic code starts (start_kernel) and 'init_mem_mapping' sets
 * up the rest of the pagetables. When it has completed it loads the cr3.
 * N.B. that baremetal would start at 'start_kernel' (and the early
 * #PF handler would create bootstrap pagetables) - so we are running
 * with the same assumptions as what to do when write_cr3 is executed
 * at this point.
 *
 * Since there are no user-page tables at all, we have two variants
 * of xen_write_cr3 - the early bootup (this one), and the late one
 * (xen_write_cr3). The reason we have to do that is that in 64-bit
 * the Linux kernel and user-space are both in ring 3 while the
 * hypervisor is in ring 0.
 */
static void __init xen_write_cr3_init(unsigned long cr3)
{
	BUG_ON(preemptible());

	xen_mc_batch();  /* disables interrupts */

	/* Update while interrupts are disabled, so its atomic with
	   respect to ipis */
	this_cpu_write(xen_cr3, cr3);

	__xen_write_cr3(true, cr3);

	xen_mc_issue(PARAVIRT_LAZY_CPU);  /* interrupts restored */
}
#endif

static int xen_pgd_alloc(struct mm_struct *mm)
{
	pgd_t *pgd = mm->pgd;
	int ret = 0;

	BUG_ON(PagePinned(virt_to_page(pgd)));

#ifdef CONFIG_X86_64
	{
		struct page *page = virt_to_page(pgd);
		pgd_t *user_pgd;

		BUG_ON(page->private != 0);

		ret = -ENOMEM;

		user_pgd = (pgd_t *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
		page->private = (unsigned long)user_pgd;

		if (user_pgd != NULL) {
#ifdef CONFIG_X86_VSYSCALL_EMULATION
			user_pgd[pgd_index(VSYSCALL_ADDR)] =
				__pgd(__pa(level3_user_vsyscall) | _PAGE_TABLE);
#endif
			ret = 0;
		}

		BUG_ON(PagePinned(virt_to_page(xen_get_user_pgd(pgd))));
	}
#endif
	return ret;
}

static void xen_pgd_free(struct mm_struct *mm, pgd_t *pgd)
{
#ifdef CONFIG_X86_64
	pgd_t *user_pgd = xen_get_user_pgd(pgd);

	if (user_pgd)
		free_page((unsigned long)user_pgd);
#endif
}

/*
 * Init-time set_pte while constructing initial pagetables, which
 * doesn't allow RO page table pages to be remapped RW.
 *
 * If there is no MFN for this PFN then this page is initially
 * ballooned out so clear the PTE (as in decrease_reservation() in
 * drivers/xen/balloon.c).
 *
 * Many of these PTE updates are done on unpinned and writable pages
 * and doing a hypercall for these is unnecessary and expensive.  At
 * this point it is not possible to tell if a page is pinned or not,
 * so always write the PTE directly and rely on Xen trapping and
 * emulating any updates as necessary.
 */
__visible pte_t xen_make_pte_init(pteval_t pte)
{
#ifdef CONFIG_X86_64
	unsigned long pfn;

	/*
	 * Pages belonging to the initial p2m list mapped outside the default
	 * address range must be mapped read-only. This region contains the
	 * page tables for mapping the p2m list, too, and page tables MUST be
	 * mapped read-only.
	 */
	pfn = (pte & PTE_PFN_MASK) >> PAGE_SHIFT;
	if (xen_start_info->mfn_list < __START_KERNEL_map &&
	    pfn >= xen_start_info->first_p2m_pfn &&
	    pfn < xen_start_info->first_p2m_pfn + xen_start_info->nr_p2m_frames)
		pte &= ~_PAGE_RW;
#endif
	pte = pte_pfn_to_mfn(pte);
	return native_make_pte(pte);
}
PV_CALLEE_SAVE_REGS_THUNK(xen_make_pte_init);

static void __init xen_set_pte_init(pte_t *ptep, pte_t pte)
{
#ifdef CONFIG_X86_32
	/* If there's an existing pte, then don't allow _PAGE_RW to be set */
	if (pte_mfn(pte) != INVALID_P2M_ENTRY
	    && pte_val_ma(*ptep) & _PAGE_PRESENT)
		pte = __pte_ma(((pte_val_ma(*ptep) & _PAGE_RW) | ~_PAGE_RW) &
			       pte_val_ma(pte));
#endif
	native_set_pte(ptep, pte);
}

/* Early in boot, while setting up the initial pagetable, assume
   everything is pinned. */
static void __init xen_alloc_pte_init(struct mm_struct *mm, unsigned long pfn)
{
#ifdef CONFIG_FLATMEM
	BUG_ON(mem_map);	/* should only be used early */
#endif
	make_lowmem_page_readonly(__va(PFN_PHYS(pfn)));
	pin_pagetable_pfn(MMUEXT_PIN_L1_TABLE, pfn);
}

/* Used for pmd and pud */
static void __init xen_alloc_pmd_init(struct mm_struct *mm, unsigned long pfn)
{
#ifdef CONFIG_FLATMEM
	BUG_ON(mem_map);	/* should only be used early */
#endif
	make_lowmem_page_readonly(__va(PFN_PHYS(pfn)));
}

/* Early release_pte assumes that all pts are pinned, since there's
   only init_mm and anything attached to that is pinned. */
static void __init xen_release_pte_init(unsigned long pfn)
{
	pin_pagetable_pfn(MMUEXT_UNPIN_TABLE, pfn);
	make_lowmem_page_readwrite(__va(PFN_PHYS(pfn)));
}

static void __init xen_release_pmd_init(unsigned long pfn)
{
	make_lowmem_page_readwrite(__va(PFN_PHYS(pfn)));
}

static inline void __pin_pagetable_pfn(unsigned cmd, unsigned long pfn)
{
	struct multicall_space mcs;
	struct mmuext_op *op;

	mcs = __xen_mc_entry(sizeof(*op));
	op = mcs.args;
	op->cmd = cmd;
	op->arg1.mfn = pfn_to_mfn(pfn);

	MULTI_mmuext_op(mcs.mc, mcs.args, 1, NULL, DOMID_SELF);
}

static inline void __set_pfn_prot(unsigned long pfn, pgprot_t prot)
{
	struct multicall_space mcs;
	unsigned long addr = (unsigned long)__va(pfn << PAGE_SHIFT);

	mcs = __xen_mc_entry(0);
	MULTI_update_va_mapping(mcs.mc, (unsigned long)addr,
				pfn_pte(pfn, prot), 0);
}

/* This needs to make sure the new pte page is pinned iff its being
   attached to a pinned pagetable. */
static inline void xen_alloc_ptpage(struct mm_struct *mm, unsigned long pfn,
				    unsigned level)
{
	bool pinned = PagePinned(virt_to_page(mm->pgd));

	trace_xen_mmu_alloc_ptpage(mm, pfn, level, pinned);

	if (pinned) {
		struct page *page = pfn_to_page(pfn);

		SetPagePinned(page);

		if (!PageHighMem(page)) {
			xen_mc_batch();

			__set_pfn_prot(pfn, PAGE_KERNEL_RO);

			if (level == PT_PTE && USE_SPLIT_PTE_PTLOCKS)
				__pin_pagetable_pfn(MMUEXT_PIN_L1_TABLE, pfn);

			xen_mc_issue(PARAVIRT_LAZY_MMU);
		} else {
			/* make sure there are no stray mappings of
			   this page */
			kmap_flush_unused();
		}
	}
}

static void xen_alloc_pte(struct mm_struct *mm, unsigned long pfn)
{
	xen_alloc_ptpage(mm, pfn, PT_PTE);
}

static void xen_alloc_pmd(struct mm_struct *mm, unsigned long pfn)
{
	xen_alloc_ptpage(mm, pfn, PT_PMD);
}

/* This should never happen until we're OK to use struct page */
static inline void xen_release_ptpage(unsigned long pfn, unsigned level)
{
	struct page *page = pfn_to_page(pfn);
	bool pinned = PagePinned(page);

	trace_xen_mmu_release_ptpage(pfn, level, pinned);

	if (pinned) {
		if (!PageHighMem(page)) {
			xen_mc_batch();

			if (level == PT_PTE && USE_SPLIT_PTE_PTLOCKS)
				__pin_pagetable_pfn(MMUEXT_UNPIN_TABLE, pfn);

			__set_pfn_prot(pfn, PAGE_KERNEL);

			xen_mc_issue(PARAVIRT_LAZY_MMU);
		}
		ClearPagePinned(page);
	}
}

static void xen_release_pte(unsigned long pfn)
{
	xen_release_ptpage(pfn, PT_PTE);
}

static void xen_release_pmd(unsigned long pfn)
{
	xen_release_ptpage(pfn, PT_PMD);
}

#if CONFIG_PGTABLE_LEVELS >= 4
static void xen_alloc_pud(struct mm_struct *mm, unsigned long pfn)
{
	xen_alloc_ptpage(mm, pfn, PT_PUD);
}

static void xen_release_pud(unsigned long pfn)
{
	xen_release_ptpage(pfn, PT_PUD);
}
#endif

void __init xen_reserve_top(void)
{
#ifdef CONFIG_X86_32
	unsigned long top = HYPERVISOR_VIRT_START;
	struct xen_platform_parameters pp;

	if (HYPERVISOR_xen_version(XENVER_platform_parameters, &pp) == 0)
		top = pp.virt_start;

	reserve_top_address(-top);
#endif	/* CONFIG_X86_32 */
}

/*
 * Like __va(), but returns address in the kernel mapping (which is
 * all we have until the physical memory mapping has been set up.
 */
static void * __init __ka(phys_addr_t paddr)
{
#ifdef CONFIG_X86_64
	return (void *)(paddr + __START_KERNEL_map);
#else
	return __va(paddr);
#endif
}

/* Convert a machine address to physical address */
static unsigned long __init m2p(phys_addr_t maddr)
{
	phys_addr_t paddr;

	maddr &= PTE_PFN_MASK;
	paddr = mfn_to_pfn(maddr >> PAGE_SHIFT) << PAGE_SHIFT;

	return paddr;
}

/* Convert a machine address to kernel virtual */
static void * __init m2v(phys_addr_t maddr)
{
	return __ka(m2p(maddr));
}

/* Set the page permissions on an identity-mapped pages */
static void __init set_page_prot_flags(void *addr, pgprot_t prot,
				       unsigned long flags)
{
	unsigned long pfn = __pa(addr) >> PAGE_SHIFT;
	pte_t pte = pfn_pte(pfn, prot);

	if (HYPERVISOR_update_va_mapping((unsigned long)addr, pte, flags))
		BUG();
}
static void __init set_page_prot(void *addr, pgprot_t prot)
{
	return set_page_prot_flags(addr, prot, UVMF_NONE);
}
#ifdef CONFIG_X86_32
static void __init xen_map_identity_early(pmd_t *pmd, unsigned long max_pfn)
{
	unsigned pmdidx, pteidx;
	unsigned ident_pte;
	unsigned long pfn;

	level1_ident_pgt = extend_brk(sizeof(pte_t) * LEVEL1_IDENT_ENTRIES,
				      PAGE_SIZE);

	ident_pte = 0;
	pfn = 0;
	for (pmdidx = 0; pmdidx < PTRS_PER_PMD && pfn < max_pfn; pmdidx++) {
		pte_t *pte_page;

		/* Reuse or allocate a page of ptes */
		if (pmd_present(pmd[pmdidx]))
			pte_page = m2v(pmd[pmdidx].pmd);
		else {
			/* Check for free pte pages */
			if (ident_pte == LEVEL1_IDENT_ENTRIES)
				break;

			pte_page = &level1_ident_pgt[ident_pte];
			ident_pte += PTRS_PER_PTE;

			pmd[pmdidx] = __pmd(__pa(pte_page) | _PAGE_TABLE);
		}

		/* Install mappings */
		for (pteidx = 0; pteidx < PTRS_PER_PTE; pteidx++, pfn++) {
			pte_t pte;

			if (pfn > max_pfn_mapped)
				max_pfn_mapped = pfn;

			if (!pte_none(pte_page[pteidx]))
				continue;

			pte = pfn_pte(pfn, PAGE_KERNEL_EXEC);
			pte_page[pteidx] = pte;
		}
	}

	for (pteidx = 0; pteidx < ident_pte; pteidx += PTRS_PER_PTE)
		set_page_prot(&level1_ident_pgt[pteidx], PAGE_KERNEL_RO);

	set_page_prot(pmd, PAGE_KERNEL_RO);
}
#endif
void __init xen_setup_machphys_mapping(void)
{
	struct xen_machphys_mapping mapping;

	if (HYPERVISOR_memory_op(XENMEM_machphys_mapping, &mapping) == 0) {
		machine_to_phys_mapping = (unsigned long *)mapping.v_start;
		machine_to_phys_nr = mapping.max_mfn + 1;
	} else {
		machine_to_phys_nr = MACH2PHYS_NR_ENTRIES;
	}
#ifdef CONFIG_X86_32
	WARN_ON((machine_to_phys_mapping + (machine_to_phys_nr - 1))
		< machine_to_phys_mapping);
#endif
}

#ifdef CONFIG_X86_64
static void __init convert_pfn_mfn(void *v)
{
	pte_t *pte = v;
	int i;

	/* All levels are converted the same way, so just treat them
	   as ptes. */
	for (i = 0; i < PTRS_PER_PTE; i++)
		pte[i] = xen_make_pte(pte[i].pte);
}
static void __init check_pt_base(unsigned long *pt_base, unsigned long *pt_end,
				 unsigned long addr)
{
	if (*pt_base == PFN_DOWN(__pa(addr))) {
		set_page_prot_flags((void *)addr, PAGE_KERNEL, UVMF_INVLPG);
		clear_page((void *)addr);
		(*pt_base)++;
	}
	if (*pt_end == PFN_DOWN(__pa(addr))) {
		set_page_prot_flags((void *)addr, PAGE_KERNEL, UVMF_INVLPG);
		clear_page((void *)addr);
		(*pt_end)--;
	}
}
/*
 * Set up the initial kernel pagetable.
 *
 * We can construct this by grafting the Xen provided pagetable into
 * head_64.S's preconstructed pagetables.  We copy the Xen L2's into
 * level2_ident_pgt, and level2_kernel_pgt.  This means that only the
 * kernel has a physical mapping to start with - but that's enough to
 * get __va working.  We need to fill in the rest of the physical
 * mapping once some sort of allocator has been set up.
 */
void __init xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn)
{
	pud_t *l3;
	pmd_t *l2;
	unsigned long addr[3];
	unsigned long pt_base, pt_end;
	unsigned i;

	/* max_pfn_mapped is the last pfn mapped in the initial memory
	 * mappings. Considering that on Xen after the kernel mappings we
	 * have the mappings of some pages that don't exist in pfn space, we
	 * set max_pfn_mapped to the last real pfn mapped. */
	if (xen_start_info->mfn_list < __START_KERNEL_map)
		max_pfn_mapped = xen_start_info->first_p2m_pfn;
	else
		max_pfn_mapped = PFN_DOWN(__pa(xen_start_info->mfn_list));

	pt_base = PFN_DOWN(__pa(xen_start_info->pt_base));
	pt_end = pt_base + xen_start_info->nr_pt_frames;

	/* Zap identity mapping */
	init_top_pgt[0] = __pgd(0);

	/* Pre-constructed entries are in pfn, so convert to mfn */
	/* L4[272] -> level3_ident_pgt  */
	/* L4[511] -> level3_kernel_pgt */
	convert_pfn_mfn(init_top_pgt);

	/* L3_i[0] -> level2_ident_pgt */
	convert_pfn_mfn(level3_ident_pgt);
	/* L3_k[510] -> level2_kernel_pgt */
	/* L3_k[511] -> level2_fixmap_pgt */
	convert_pfn_mfn(level3_kernel_pgt);

	/* L3_k[511][506] -> level1_fixmap_pgt */
	convert_pfn_mfn(level2_fixmap_pgt);

	/* We get [511][511] and have Xen's version of level2_kernel_pgt */
	l3 = m2v(pgd[pgd_index(__START_KERNEL_map)].pgd);
	l2 = m2v(l3[pud_index(__START_KERNEL_map)].pud);

	addr[0] = (unsigned long)pgd;
	addr[1] = (unsigned long)l3;
	addr[2] = (unsigned long)l2;
	/* Graft it onto L4[272][0]. Note that we creating an aliasing problem:
	 * Both L4[272][0] and L4[511][510] have entries that point to the same
	 * L2 (PMD) tables. Meaning that if you modify it in __va space
	 * it will be also modified in the __ka space! (But if you just
	 * modify the PMD table to point to other PTE's or none, then you
	 * are OK - which is what cleanup_highmap does) */
	copy_page(level2_ident_pgt, l2);
	/* Graft it onto L4[511][510] */
	copy_page(level2_kernel_pgt, l2);

	/* Copy the initial P->M table mappings if necessary. */
	i = pgd_index(xen_start_info->mfn_list);
	if (i && i < pgd_index(__START_KERNEL_map))
		init_top_pgt[i] = ((pgd_t *)xen_start_info->pt_base)[i];

	/* Make pagetable pieces RO */
	set_page_prot(init_top_pgt, PAGE_KERNEL_RO);
	set_page_prot(level3_ident_pgt, PAGE_KERNEL_RO);
	set_page_prot(level3_kernel_pgt, PAGE_KERNEL_RO);
	set_page_prot(level3_user_vsyscall, PAGE_KERNEL_RO);
	set_page_prot(level2_ident_pgt, PAGE_KERNEL_RO);
	set_page_prot(level2_kernel_pgt, PAGE_KERNEL_RO);
	set_page_prot(level2_fixmap_pgt, PAGE_KERNEL_RO);
	set_page_prot(level1_fixmap_pgt, PAGE_KERNEL_RO);

	/* Pin down new L4 */
	pin_pagetable_pfn(MMUEXT_PIN_L4_TABLE,
			  PFN_DOWN(__pa_symbol(init_top_pgt)));

	/* Unpin Xen-provided one */
	pin_pagetable_pfn(MMUEXT_UNPIN_TABLE, PFN_DOWN(__pa(pgd)));

	/*
	 * At this stage there can be no user pgd, and no page structure to
	 * attach it to, so make sure we just set kernel pgd.
	 */
	xen_mc_batch();
	__xen_write_cr3(true, __pa(init_top_pgt));
	xen_mc_issue(PARAVIRT_LAZY_CPU);

	/* We can't that easily rip out L3 and L2, as the Xen pagetables are
	 * set out this way: [L4], [L1], [L2], [L3], [L1], [L1] ...  for
	 * the initial domain. For guests using the toolstack, they are in:
	 * [L4], [L3], [L2], [L1], [L1], order .. So for dom0 we can only
	 * rip out the [L4] (pgd), but for guests we shave off three pages.
	 */
	for (i = 0; i < ARRAY_SIZE(addr); i++)
		check_pt_base(&pt_base, &pt_end, addr[i]);

	/* Our (by three pages) smaller Xen pagetable that we are using */
	xen_pt_base = PFN_PHYS(pt_base);
	xen_pt_size = (pt_end - pt_base) * PAGE_SIZE;
	memblock_reserve(xen_pt_base, xen_pt_size);

	/* Revector the xen_start_info */
	xen_start_info = (struct start_info *)__va(__pa(xen_start_info));
}

/*
 * Read a value from a physical address.
 */
static unsigned long __init xen_read_phys_ulong(phys_addr_t addr)
{
	unsigned long *vaddr;
	unsigned long val;

	vaddr = early_memremap_ro(addr, sizeof(val));
	val = *vaddr;
	early_memunmap(vaddr, sizeof(val));
	return val;
}

/*
 * Translate a virtual address to a physical one without relying on mapped
 * page tables. Don't rely on big pages being aligned in (guest) physical
 * space!
 */
static phys_addr_t __init xen_early_virt_to_phys(unsigned long vaddr)
{
	phys_addr_t pa;
	pgd_t pgd;
	pud_t pud;
	pmd_t pmd;
	pte_t pte;

	pa = read_cr3_pa();
	pgd = native_make_pgd(xen_read_phys_ulong(pa + pgd_index(vaddr) *
						       sizeof(pgd)));
	if (!pgd_present(pgd))
		return 0;

	pa = pgd_val(pgd) & PTE_PFN_MASK;
	pud = native_make_pud(xen_read_phys_ulong(pa + pud_index(vaddr) *
						       sizeof(pud)));
	if (!pud_present(pud))
		return 0;
	pa = pud_val(pud) & PTE_PFN_MASK;
	if (pud_large(pud))
		return pa + (vaddr & ~PUD_MASK);

	pmd = native_make_pmd(xen_read_phys_ulong(pa + pmd_index(vaddr) *
						       sizeof(pmd)));
	if (!pmd_present(pmd))
		return 0;
	pa = pmd_val(pmd) & PTE_PFN_MASK;
	if (pmd_large(pmd))
		return pa + (vaddr & ~PMD_MASK);

	pte = native_make_pte(xen_read_phys_ulong(pa + pte_index(vaddr) *
						       sizeof(pte)));
	if (!pte_present(pte))
		return 0;
	pa = pte_pfn(pte) << PAGE_SHIFT;

	return pa | (vaddr & ~PAGE_MASK);
}

/*
 * Find a new area for the hypervisor supplied p2m list and relocate the p2m to
 * this area.
 */
void __init xen_relocate_p2m(void)
{
	phys_addr_t size, new_area, pt_phys, pmd_phys, pud_phys, p4d_phys;
	unsigned long p2m_pfn, p2m_pfn_end, n_frames, pfn, pfn_end;
	int n_pte, n_pt, n_pmd, n_pud, n_p4d, idx_pte, idx_pt, idx_pmd, idx_pud, idx_p4d;
	pte_t *pt;
	pmd_t *pmd;
	pud_t *pud;
	p4d_t *p4d = NULL;
	pgd_t *pgd;
	unsigned long *new_p2m;
	int save_pud;

	size = PAGE_ALIGN(xen_start_info->nr_pages * sizeof(unsigned long));
	n_pte = roundup(size, PAGE_SIZE) >> PAGE_SHIFT;
	n_pt = roundup(size, PMD_SIZE) >> PMD_SHIFT;
	n_pmd = roundup(size, PUD_SIZE) >> PUD_SHIFT;
	n_pud = roundup(size, P4D_SIZE) >> P4D_SHIFT;
	if (PTRS_PER_P4D > 1)
		n_p4d = roundup(size, PGDIR_SIZE) >> PGDIR_SHIFT;
	else
		n_p4d = 0;
	n_frames = n_pte + n_pt + n_pmd + n_pud + n_p4d;

	new_area = xen_find_free_area(PFN_PHYS(n_frames));
	if (!new_area) {
		xen_raw_console_write("Can't find new memory area for p2m needed due to E820 map conflict\n");
		BUG();
	}

	/*
	 * Setup the page tables for addressing the new p2m list.
	 * We have asked the hypervisor to map the p2m list at the user address
	 * PUD_SIZE. It may have done so, or it may have used a kernel space
	 * address depending on the Xen version.
	 * To avoid any possible virtual address collision, just use
	 * 2 * PUD_SIZE for the new area.
	 */
	p4d_phys = new_area;
	pud_phys = p4d_phys + PFN_PHYS(n_p4d);
	pmd_phys = pud_phys + PFN_PHYS(n_pud);
	pt_phys = pmd_phys + PFN_PHYS(n_pmd);
	p2m_pfn = PFN_DOWN(pt_phys) + n_pt;

	pgd = __va(read_cr3_pa());
	new_p2m = (unsigned long *)(2 * PGDIR_SIZE);
	idx_p4d = 0;
	save_pud = n_pud;
	do {
		if (n_p4d > 0) {
			p4d = early_memremap(p4d_phys, PAGE_SIZE);
			clear_page(p4d);
			n_pud = min(save_pud, PTRS_PER_P4D);
		}
		for (idx_pud = 0; idx_pud < n_pud; idx_pud++) {
			pud = early_memremap(pud_phys, PAGE_SIZE);
			clear_page(pud);
			for (idx_pmd = 0; idx_pmd < min(n_pmd, PTRS_PER_PUD);
				 idx_pmd++) {
				pmd = early_memremap(pmd_phys, PAGE_SIZE);
				clear_page(pmd);
				for (idx_pt = 0; idx_pt < min(n_pt, PTRS_PER_PMD);
					 idx_pt++) {
					pt = early_memremap(pt_phys, PAGE_SIZE);
					clear_page(pt);
					for (idx_pte = 0;
						 idx_pte < min(n_pte, PTRS_PER_PTE);
						 idx_pte++) {
						set_pte(pt + idx_pte,
								pfn_pte(p2m_pfn, PAGE_KERNEL));
						p2m_pfn++;
					}
					n_pte -= PTRS_PER_PTE;
					early_memunmap(pt, PAGE_SIZE);
					make_lowmem_page_readonly(__va(pt_phys));
					pin_pagetable_pfn(MMUEXT_PIN_L1_TABLE,
							PFN_DOWN(pt_phys));
					set_pmd(pmd + idx_pt,
							__pmd(_PAGE_TABLE | pt_phys));
					pt_phys += PAGE_SIZE;
				}
				n_pt -= PTRS_PER_PMD;
				early_memunmap(pmd, PAGE_SIZE);
				make_lowmem_page_readonly(__va(pmd_phys));
				pin_pagetable_pfn(MMUEXT_PIN_L2_TABLE,
						PFN_DOWN(pmd_phys));
				set_pud(pud + idx_pmd, __pud(_PAGE_TABLE | pmd_phys));
				pmd_phys += PAGE_SIZE;
			}
			n_pmd -= PTRS_PER_PUD;
			early_memunmap(pud, PAGE_SIZE);
			make_lowmem_page_readonly(__va(pud_phys));
			pin_pagetable_pfn(MMUEXT_PIN_L3_TABLE, PFN_DOWN(pud_phys));
			if (n_p4d > 0)
				set_p4d(p4d + idx_pud, __p4d(_PAGE_TABLE | pud_phys));
			else
				set_pgd(pgd + 2 + idx_pud, __pgd(_PAGE_TABLE | pud_phys));
			pud_phys += PAGE_SIZE;
		}
		if (n_p4d > 0) {
			save_pud -= PTRS_PER_P4D;
			early_memunmap(p4d, PAGE_SIZE);
			make_lowmem_page_readonly(__va(p4d_phys));
			pin_pagetable_pfn(MMUEXT_PIN_L4_TABLE, PFN_DOWN(p4d_phys));
			set_pgd(pgd + 2 + idx_p4d, __pgd(_PAGE_TABLE | p4d_phys));
			p4d_phys += PAGE_SIZE;
		}
	} while (++idx_p4d < n_p4d);

	/* Now copy the old p2m info to the new area. */
	memcpy(new_p2m, xen_p2m_addr, size);
	xen_p2m_addr = new_p2m;

	/* Release the old p2m list and set new list info. */
	p2m_pfn = PFN_DOWN(xen_early_virt_to_phys(xen_start_info->mfn_list));
	BUG_ON(!p2m_pfn);
	p2m_pfn_end = p2m_pfn + PFN_DOWN(size);

	if (xen_start_info->mfn_list < __START_KERNEL_map) {
		pfn = xen_start_info->first_p2m_pfn;
		pfn_end = xen_start_info->first_p2m_pfn +
			  xen_start_info->nr_p2m_frames;
		set_pgd(pgd + 1, __pgd(0));
	} else {
		pfn = p2m_pfn;
		pfn_end = p2m_pfn_end;
	}

	memblock_free(PFN_PHYS(pfn), PAGE_SIZE * (pfn_end - pfn));
	while (pfn < pfn_end) {
		if (pfn == p2m_pfn) {
			pfn = p2m_pfn_end;
			continue;
		}
		make_lowmem_page_readwrite(__va(PFN_PHYS(pfn)));
		pfn++;
	}

	xen_start_info->mfn_list = (unsigned long)xen_p2m_addr;
	xen_start_info->first_p2m_pfn =  PFN_DOWN(new_area);
	xen_start_info->nr_p2m_frames = n_frames;
}

#else	/* !CONFIG_X86_64 */
static RESERVE_BRK_ARRAY(pmd_t, initial_kernel_pmd, PTRS_PER_PMD);
static RESERVE_BRK_ARRAY(pmd_t, swapper_kernel_pmd, PTRS_PER_PMD);

static void __init xen_write_cr3_init(unsigned long cr3)
{
	unsigned long pfn = PFN_DOWN(__pa(swapper_pg_dir));

	BUG_ON(read_cr3_pa() != __pa(initial_page_table));
	BUG_ON(cr3 != __pa(swapper_pg_dir));

	/*
	 * We are switching to swapper_pg_dir for the first time (from
	 * initial_page_table) and therefore need to mark that page
	 * read-only and then pin it.
	 *
	 * Xen disallows sharing of kernel PMDs for PAE
	 * guests. Therefore we must copy the kernel PMD from
	 * initial_page_table into a new kernel PMD to be used in
	 * swapper_pg_dir.
	 */
	swapper_kernel_pmd =
		extend_brk(sizeof(pmd_t) * PTRS_PER_PMD, PAGE_SIZE);
	copy_page(swapper_kernel_pmd, initial_kernel_pmd);
	swapper_pg_dir[KERNEL_PGD_BOUNDARY] =
		__pgd(__pa(swapper_kernel_pmd) | _PAGE_PRESENT);
	set_page_prot(swapper_kernel_pmd, PAGE_KERNEL_RO);

	set_page_prot(swapper_pg_dir, PAGE_KERNEL_RO);
	xen_write_cr3(cr3);
	pin_pagetable_pfn(MMUEXT_PIN_L3_TABLE, pfn);

	pin_pagetable_pfn(MMUEXT_UNPIN_TABLE,
			  PFN_DOWN(__pa(initial_page_table)));
	set_page_prot(initial_page_table, PAGE_KERNEL);
	set_page_prot(initial_kernel_pmd, PAGE_KERNEL);

	pv_mmu_ops.write_cr3 = &xen_write_cr3;
}

/*
 * For 32 bit domains xen_start_info->pt_base is the pgd address which might be
 * not the first page table in the page table pool.
 * Iterate through the initial page tables to find the real page table base.
 */
static phys_addr_t xen_find_pt_base(pmd_t *pmd)
{
	phys_addr_t pt_base, paddr;
	unsigned pmdidx;

	pt_base = min(__pa(xen_start_info->pt_base), __pa(pmd));

	for (pmdidx = 0; pmdidx < PTRS_PER_PMD; pmdidx++)
		if (pmd_present(pmd[pmdidx]) && !pmd_large(pmd[pmdidx])) {
			paddr = m2p(pmd[pmdidx].pmd);
			pt_base = min(pt_base, paddr);
		}

	return pt_base;
}

void __init xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn)
{
	pmd_t *kernel_pmd;

	kernel_pmd = m2v(pgd[KERNEL_PGD_BOUNDARY].pgd);

	xen_pt_base = xen_find_pt_base(kernel_pmd);
	xen_pt_size = xen_start_info->nr_pt_frames * PAGE_SIZE;

	initial_kernel_pmd =
		extend_brk(sizeof(pmd_t) * PTRS_PER_PMD, PAGE_SIZE);

	max_pfn_mapped = PFN_DOWN(xen_pt_base + xen_pt_size + 512 * 1024);

	copy_page(initial_kernel_pmd, kernel_pmd);

	xen_map_identity_early(initial_kernel_pmd, max_pfn);

	copy_page(initial_page_table, pgd);
	initial_page_table[KERNEL_PGD_BOUNDARY] =
		__pgd(__pa(initial_kernel_pmd) | _PAGE_PRESENT);

	set_page_prot(initial_kernel_pmd, PAGE_KERNEL_RO);
	set_page_prot(initial_page_table, PAGE_KERNEL_RO);
	set_page_prot(empty_zero_page, PAGE_KERNEL_RO);

	pin_pagetable_pfn(MMUEXT_UNPIN_TABLE, PFN_DOWN(__pa(pgd)));

	pin_pagetable_pfn(MMUEXT_PIN_L3_TABLE,
			  PFN_DOWN(__pa(initial_page_table)));
	xen_write_cr3(__pa(initial_page_table));

	memblock_reserve(xen_pt_base, xen_pt_size);
}
#endif	/* CONFIG_X86_64 */

void __init xen_reserve_special_pages(void)
{
	phys_addr_t paddr;

	memblock_reserve(__pa(xen_start_info), PAGE_SIZE);
	if (xen_start_info->store_mfn) {
		paddr = PFN_PHYS(mfn_to_pfn(xen_start_info->store_mfn));
		memblock_reserve(paddr, PAGE_SIZE);
	}
	if (!xen_initial_domain()) {
		paddr = PFN_PHYS(mfn_to_pfn(xen_start_info->console.domU.mfn));
		memblock_reserve(paddr, PAGE_SIZE);
	}
}

void __init xen_pt_check_e820(void)
{
	if (xen_is_e820_reserved(xen_pt_base, xen_pt_size)) {
		xen_raw_console_write("Xen hypervisor allocated page table memory conflicts with E820 map\n");
		BUG();
	}
}

static unsigned char dummy_mapping[PAGE_SIZE] __page_aligned_bss;

static void xen_set_fixmap(unsigned idx, phys_addr_t phys, pgprot_t prot)
{
	pte_t pte;

	phys >>= PAGE_SHIFT;

	switch (idx) {
	case FIX_BTMAP_END ... FIX_BTMAP_BEGIN:
	case FIX_RO_IDT:
#ifdef CONFIG_X86_32
	case FIX_WP_TEST:
# ifdef CONFIG_HIGHMEM
	case FIX_KMAP_BEGIN ... FIX_KMAP_END:
# endif
#elif defined(CONFIG_X86_VSYSCALL_EMULATION)
	case VSYSCALL_PAGE:
#endif
	case FIX_TEXT_POKE0:
	case FIX_TEXT_POKE1:
	case FIX_GDT_REMAP_BEGIN ... FIX_GDT_REMAP_END:
		/* All local page mappings */
		pte = pfn_pte(phys, prot);
		break;

#ifdef CONFIG_X86_LOCAL_APIC
	case FIX_APIC_BASE:	/* maps dummy local APIC */
		pte = pfn_pte(PFN_DOWN(__pa(dummy_mapping)), PAGE_KERNEL);
		break;
#endif

#ifdef CONFIG_X86_IO_APIC
	case FIX_IO_APIC_BASE_0 ... FIX_IO_APIC_BASE_END:
		/*
		 * We just don't map the IO APIC - all access is via
		 * hypercalls.  Keep the address in the pte for reference.
		 */
		pte = pfn_pte(PFN_DOWN(__pa(dummy_mapping)), PAGE_KERNEL);
		break;
#endif

	case FIX_PARAVIRT_BOOTMAP:
		/* This is an MFN, but it isn't an IO mapping from the
		   IO domain */
		pte = mfn_pte(phys, prot);
		break;

	default:
		/* By default, set_fixmap is used for hardware mappings */
		pte = mfn_pte(phys, prot);
		break;
	}

	__native_set_fixmap(idx, pte);

#ifdef CONFIG_X86_VSYSCALL_EMULATION
	/* Replicate changes to map the vsyscall page into the user
	   pagetable vsyscall mapping. */
	if (idx == VSYSCALL_PAGE) {
		unsigned long vaddr = __fix_to_virt(idx);
		set_pte_vaddr_pud(level3_user_vsyscall, vaddr, pte);
	}
#endif
}

static void __init xen_post_allocator_init(void)
{
	pv_mmu_ops.set_pte = xen_set_pte;
	pv_mmu_ops.set_pmd = xen_set_pmd;
	pv_mmu_ops.set_pud = xen_set_pud;
#if CONFIG_PGTABLE_LEVELS >= 4
	pv_mmu_ops.set_p4d = xen_set_p4d;
#endif

	/* This will work as long as patching hasn't happened yet
	   (which it hasn't) */
	pv_mmu_ops.alloc_pte = xen_alloc_pte;
	pv_mmu_ops.alloc_pmd = xen_alloc_pmd;
	pv_mmu_ops.release_pte = xen_release_pte;
	pv_mmu_ops.release_pmd = xen_release_pmd;
#if CONFIG_PGTABLE_LEVELS >= 4
	pv_mmu_ops.alloc_pud = xen_alloc_pud;
	pv_mmu_ops.release_pud = xen_release_pud;
#endif
	pv_mmu_ops.make_pte = PV_CALLEE_SAVE(xen_make_pte);

#ifdef CONFIG_X86_64
	pv_mmu_ops.write_cr3 = &xen_write_cr3;
	SetPagePinned(virt_to_page(level3_user_vsyscall));
#endif
	xen_mark_init_mm_pinned();
}

static void xen_leave_lazy_mmu(void)
{
	preempt_disable();
	xen_mc_flush();
	paravirt_leave_lazy_mmu();
	preempt_enable();
}

static const struct pv_mmu_ops xen_mmu_ops __initconst = {
	.read_cr2 = xen_read_cr2,
	.write_cr2 = xen_write_cr2,

	.read_cr3 = xen_read_cr3,
	.write_cr3 = xen_write_cr3_init,

	.flush_tlb_user = xen_flush_tlb,
	.flush_tlb_kernel = xen_flush_tlb,
	.flush_tlb_single = xen_flush_tlb_single,
	.flush_tlb_others = xen_flush_tlb_others,

	.pgd_alloc = xen_pgd_alloc,
	.pgd_free = xen_pgd_free,

	.alloc_pte = xen_alloc_pte_init,
	.release_pte = xen_release_pte_init,
	.alloc_pmd = xen_alloc_pmd_init,
	.release_pmd = xen_release_pmd_init,

	.set_pte = xen_set_pte_init,
	.set_pte_at = xen_set_pte_at,
	.set_pmd = xen_set_pmd_hyper,

	.ptep_modify_prot_start = __ptep_modify_prot_start,
	.ptep_modify_prot_commit = __ptep_modify_prot_commit,

	.pte_val = PV_CALLEE_SAVE(xen_pte_val),
	.pgd_val = PV_CALLEE_SAVE(xen_pgd_val),

	.make_pte = PV_CALLEE_SAVE(xen_make_pte_init),
	.make_pgd = PV_CALLEE_SAVE(xen_make_pgd),

#ifdef CONFIG_X86_PAE
	.set_pte_atomic = xen_set_pte_atomic,
	.pte_clear = xen_pte_clear,
	.pmd_clear = xen_pmd_clear,
#endif	/* CONFIG_X86_PAE */
	.set_pud = xen_set_pud_hyper,

	.make_pmd = PV_CALLEE_SAVE(xen_make_pmd),
	.pmd_val = PV_CALLEE_SAVE(xen_pmd_val),

#if CONFIG_PGTABLE_LEVELS >= 4
	.pud_val = PV_CALLEE_SAVE(xen_pud_val),
	.make_pud = PV_CALLEE_SAVE(xen_make_pud),
	.set_p4d = xen_set_p4d_hyper,

	.alloc_pud = xen_alloc_pmd_init,
	.release_pud = xen_release_pmd_init,
#endif	/* CONFIG_PGTABLE_LEVELS == 4 */

	.activate_mm = xen_activate_mm,
	.dup_mmap = xen_dup_mmap,
	.exit_mmap = xen_exit_mmap,

	.lazy_mode = {
		.enter = paravirt_enter_lazy_mmu,
		.leave = xen_leave_lazy_mmu,
		.flush = paravirt_flush_lazy_mmu,
	},

	.set_fixmap = xen_set_fixmap,
};

void __init xen_init_mmu_ops(void)
{
	x86_init.paging.pagetable_init = xen_pagetable_init;

	pv_mmu_ops = xen_mmu_ops;

	memset(dummy_mapping, 0xff, PAGE_SIZE);
}

/* Protected by xen_reservation_lock. */
#define MAX_CONTIG_ORDER 9 /* 2MB */
static unsigned long discontig_frames[1<<MAX_CONTIG_ORDER];

#define VOID_PTE (mfn_pte(0, __pgprot(0)))
static void xen_zap_pfn_range(unsigned long vaddr, unsigned int order,
				unsigned long *in_frames,
				unsigned long *out_frames)
{
	int i;
	struct multicall_space mcs;

	xen_mc_batch();
	for (i = 0; i < (1UL<<order); i++, vaddr += PAGE_SIZE) {
		mcs = __xen_mc_entry(0);

		if (in_frames)
			in_frames[i] = virt_to_mfn(vaddr);

		MULTI_update_va_mapping(mcs.mc, vaddr, VOID_PTE, 0);
		__set_phys_to_machine(virt_to_pfn(vaddr), INVALID_P2M_ENTRY);

		if (out_frames)
			out_frames[i] = virt_to_pfn(vaddr);
	}
	xen_mc_issue(0);
}

/*
 * Update the pfn-to-mfn mappings for a virtual address range, either to
 * point to an array of mfns, or contiguously from a single starting
 * mfn.
 */
static void xen_remap_exchanged_ptes(unsigned long vaddr, int order,
				     unsigned long *mfns,
				     unsigned long first_mfn)
{
	unsigned i, limit;
	unsigned long mfn;

	xen_mc_batch();

	limit = 1u << order;
	for (i = 0; i < limit; i++, vaddr += PAGE_SIZE) {
		struct multicall_space mcs;
		unsigned flags;

		mcs = __xen_mc_entry(0);
		if (mfns)
			mfn = mfns[i];
		else
			mfn = first_mfn + i;

		if (i < (limit - 1))
			flags = 0;
		else {
			if (order == 0)
				flags = UVMF_INVLPG | UVMF_ALL;
			else
				flags = UVMF_TLB_FLUSH | UVMF_ALL;
		}

		MULTI_update_va_mapping(mcs.mc, vaddr,
				mfn_pte(mfn, PAGE_KERNEL), flags);

		set_phys_to_machine(virt_to_pfn(vaddr), mfn);
	}

	xen_mc_issue(0);
}

/*
 * Perform the hypercall to exchange a region of our pfns to point to
 * memory with the required contiguous alignment.  Takes the pfns as
 * input, and populates mfns as output.
 *
 * Returns a success code indicating whether the hypervisor was able to
 * satisfy the request or not.
 */
static int xen_exchange_memory(unsigned long extents_in, unsigned int order_in,
			       unsigned long *pfns_in,
			       unsigned long extents_out,
			       unsigned int order_out,
			       unsigned long *mfns_out,
			       unsigned int address_bits)
{
	long rc;
	int success;

	struct xen_memory_exchange exchange = {
		.in = {
			.nr_extents   = extents_in,
			.extent_order = order_in,
			.extent_start = pfns_in,
			.domid        = DOMID_SELF
		},
		.out = {
			.nr_extents   = extents_out,
			.extent_order = order_out,
			.extent_start = mfns_out,
			.address_bits = address_bits,
			.domid        = DOMID_SELF
		}
	};

	BUG_ON(extents_in << order_in != extents_out << order_out);

	rc = HYPERVISOR_memory_op(XENMEM_exchange, &exchange);
	success = (exchange.nr_exchanged == extents_in);

	BUG_ON(!success && ((exchange.nr_exchanged != 0) || (rc == 0)));
	BUG_ON(success && (rc != 0));

	return success;
}

int xen_create_contiguous_region(phys_addr_t pstart, unsigned int order,
				 unsigned int address_bits,
				 dma_addr_t *dma_handle)
{
	unsigned long *in_frames = discontig_frames, out_frame;
	unsigned long  flags;
	int            success;
	unsigned long vstart = (unsigned long)phys_to_virt(pstart);

	/*
	 * Currently an auto-translated guest will not perform I/O, nor will
	 * it require PAE page directories below 4GB. Therefore any calls to
	 * this function are redundant and can be ignored.
	 */

	if (unlikely(order > MAX_CONTIG_ORDER))
		return -ENOMEM;

	memset((void *) vstart, 0, PAGE_SIZE << order);

	spin_lock_irqsave(&xen_reservation_lock, flags);

	/* 1. Zap current PTEs, remembering MFNs. */
	xen_zap_pfn_range(vstart, order, in_frames, NULL);

	/* 2. Get a new contiguous memory extent. */
	out_frame = virt_to_pfn(vstart);
	success = xen_exchange_memory(1UL << order, 0, in_frames,
				      1, order, &out_frame,
				      address_bits);

	/* 3. Map the new extent in place of old pages. */
	if (success)
		xen_remap_exchanged_ptes(vstart, order, NULL, out_frame);
	else
		xen_remap_exchanged_ptes(vstart, order, in_frames, 0);

	spin_unlock_irqrestore(&xen_reservation_lock, flags);

	*dma_handle = virt_to_machine(vstart).maddr;
	return success ? 0 : -ENOMEM;
}
EXPORT_SYMBOL_GPL(xen_create_contiguous_region);

void xen_destroy_contiguous_region(phys_addr_t pstart, unsigned int order)
{
	unsigned long *out_frames = discontig_frames, in_frame;
	unsigned long  flags;
	int success;
	unsigned long vstart;

	if (unlikely(order > MAX_CONTIG_ORDER))
		return;

	vstart = (unsigned long)phys_to_virt(pstart);
	memset((void *) vstart, 0, PAGE_SIZE << order);

	spin_lock_irqsave(&xen_reservation_lock, flags);

	/* 1. Find start MFN of contiguous extent. */
	in_frame = virt_to_mfn(vstart);

	/* 2. Zap current PTEs. */
	xen_zap_pfn_range(vstart, order, NULL, out_frames);

	/* 3. Do the exchange for non-contiguous MFNs. */
	success = xen_exchange_memory(1, order, &in_frame, 1UL << order,
					0, out_frames, 0);

	/* 4. Map new pages in place of old pages. */
	if (success)
		xen_remap_exchanged_ptes(vstart, order, out_frames, 0);
	else
		xen_remap_exchanged_ptes(vstart, order, NULL, in_frame);

	spin_unlock_irqrestore(&xen_reservation_lock, flags);
}
EXPORT_SYMBOL_GPL(xen_destroy_contiguous_region);

#ifdef CONFIG_KEXEC_CORE
phys_addr_t paddr_vmcoreinfo_note(void)
{
	if (xen_pv_domain())
		return virt_to_machine(vmcoreinfo_note).maddr;
	else
		return __pa(vmcoreinfo_note);
}
#endif /* CONFIG_KEXEC_CORE */