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Commit b5eafe92 authored by Jeremy Fitzhardinge's avatar Jeremy Fitzhardinge Committed by Konrad Rzeszutek Wilk
Browse files

xen: move p2m handling to separate file 



Signed-off-by: default avatarJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent 8d3eaea2

arch/x86/xen/Makefile

+2 −1
Original line number Diff line number Diff line
@@ -12,7 +12,8 @@ CFLAGS_mmu.o := $(nostackp) 


obj-y		:= enlighten.o setup.o multicalls.o mmu.o irq.o \

			time.o xen-asm.o xen-asm_$(BITS).o \

			grant-table.o suspend.o platform-pci-unplug.o

			grant-table.o suspend.o platform-pci-unplug.o \

			p2m.o



obj-$(CONFIG_SMP)		+= smp.o

obj-$(CONFIG_PARAVIRT_SPINLOCKS)+= spinlock.o

arch/x86/xen/mmu.c

+0 −365
Original line number Diff line number Diff line
@@ -173,371 +173,6 @@ DEFINE_PER_CPU(unsigned long, xen_current_cr3); /* actual vcpu cr3 */ 
 */

#define USER_LIMIT	((STACK_TOP_MAX + PGDIR_SIZE - 1) & PGDIR_MASK)



/*

 * Xen leaves the responsibility for maintaining p2m mappings to the

 * guests themselves, but it must also access and update the p2m array

 * during suspend/resume when all the pages are reallocated.

 *

 * The p2m table is logically a flat array, but we implement it as a

 * three-level tree to allow the address space to be sparse.

 *

 *                               Xen

 *                                |

 *     p2m_top              p2m_top_mfn

 *       /  \                   /   \

 * p2m_mid p2m_mid	p2m_mid_mfn p2m_mid_mfn

 *    / \      / \         /           /

 *  p2m p2m p2m p2m p2m p2m p2m ...

 *

 * The p2m_mid_mfn pages are mapped by p2m_top_mfn_p.

 *

 * The p2m_top and p2m_top_mfn levels are limited to 1 page, so the

 * maximum representable pseudo-physical address space is:

 *  P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE pages

 *

 * P2M_PER_PAGE depends on the architecture, as a mfn is always

 * unsigned long (8 bytes on 64-bit, 4 bytes on 32), leading to

 * 512 and 1024 entries respectively. 

 */



unsigned long xen_max_p2m_pfn __read_mostly;



#define P2M_PER_PAGE		(PAGE_SIZE / sizeof(unsigned long))

#define P2M_MID_PER_PAGE	(PAGE_SIZE / sizeof(unsigned long *))

#define P2M_TOP_PER_PAGE	(PAGE_SIZE / sizeof(unsigned long **))



#define MAX_P2M_PFN		(P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE)



/* Placeholders for holes in the address space */

static RESERVE_BRK_ARRAY(unsigned long, p2m_missing, P2M_PER_PAGE);

static RESERVE_BRK_ARRAY(unsigned long *, p2m_mid_missing, P2M_MID_PER_PAGE);

static RESERVE_BRK_ARRAY(unsigned long, p2m_mid_missing_mfn, P2M_MID_PER_PAGE);



static RESERVE_BRK_ARRAY(unsigned long **, p2m_top, P2M_TOP_PER_PAGE);

static RESERVE_BRK_ARRAY(unsigned long, p2m_top_mfn, P2M_TOP_PER_PAGE);

static RESERVE_BRK_ARRAY(unsigned long *, p2m_top_mfn_p, P2M_TOP_PER_PAGE);



RESERVE_BRK(p2m_mid, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID_PER_PAGE)));

RESERVE_BRK(p2m_mid_mfn, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID_PER_PAGE)));



static inline unsigned p2m_top_index(unsigned long pfn)

{

	BUG_ON(pfn >= MAX_P2M_PFN);

	return pfn / (P2M_MID_PER_PAGE * P2M_PER_PAGE);

}



static inline unsigned p2m_mid_index(unsigned long pfn)

{

	return (pfn / P2M_PER_PAGE) % P2M_MID_PER_PAGE;

}



static inline unsigned p2m_index(unsigned long pfn)

{

	return pfn % P2M_PER_PAGE;

}



static void p2m_top_init(unsigned long ***top)

{

	unsigned i;



	for (i = 0; i < P2M_TOP_PER_PAGE; i++)

		top[i] = p2m_mid_missing;

}



static void p2m_top_mfn_init(unsigned long *top)

{

	unsigned i;



	for (i = 0; i < P2M_TOP_PER_PAGE; i++)

		top[i] = virt_to_mfn(p2m_mid_missing_mfn);

}



static void p2m_top_mfn_p_init(unsigned long **top)

{

	unsigned i;



	for (i = 0; i < P2M_TOP_PER_PAGE; i++)

		top[i] = p2m_mid_missing_mfn;

}



static void p2m_mid_init(unsigned long **mid)

{

	unsigned i;



	for (i = 0; i < P2M_MID_PER_PAGE; i++)

		mid[i] = p2m_missing;

}



static void p2m_mid_mfn_init(unsigned long *mid)

{

	unsigned i;



	for (i = 0; i < P2M_MID_PER_PAGE; i++)

		mid[i] = virt_to_mfn(p2m_missing);

}



static void p2m_init(unsigned long *p2m)

{

	unsigned i;



	for (i = 0; i < P2M_MID_PER_PAGE; i++)

		p2m[i] = INVALID_P2M_ENTRY;

}



/*

 * Build the parallel p2m_top_mfn and p2m_mid_mfn structures

 *

 * This is called both at boot time, and after resuming from suspend:

 * - At boot time we're called very early, and must use extend_brk()

 *   to allocate memory.

 *

 * - After resume we're called from within stop_machine, but the mfn

 *   tree should alreay be completely allocated.

 */

void xen_build_mfn_list_list(void)

{

	unsigned long pfn;



	/* Pre-initialize p2m_top_mfn to be completely missing */

	if (p2m_top_mfn == NULL) {

		p2m_mid_missing_mfn = extend_brk(PAGE_SIZE, PAGE_SIZE);

		p2m_mid_mfn_init(p2m_mid_missing_mfn);



		p2m_top_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE);

		p2m_top_mfn_p_init(p2m_top_mfn_p);



		p2m_top_mfn = extend_brk(PAGE_SIZE, PAGE_SIZE);

		p2m_top_mfn_init(p2m_top_mfn);

	} else {

		/* Reinitialise, mfn's all change after migration */

		p2m_mid_mfn_init(p2m_mid_missing_mfn);

	}



	for (pfn = 0; pfn < xen_max_p2m_pfn; pfn += P2M_PER_PAGE) {

		unsigned topidx = p2m_top_index(pfn);

		unsigned mididx = p2m_mid_index(pfn);

		unsigned long **mid;

		unsigned long *mid_mfn_p;



		mid = p2m_top[topidx];

		mid_mfn_p = p2m_top_mfn_p[topidx];



		/* Don't bother allocating any mfn mid levels if

		 * they're just missing, just update the stored mfn,

		 * since all could have changed over a migrate.

		 */

		if (mid == p2m_mid_missing) {

			BUG_ON(mididx);

			BUG_ON(mid_mfn_p != p2m_mid_missing_mfn);

			p2m_top_mfn[topidx] = virt_to_mfn(p2m_mid_missing_mfn);

			pfn += (P2M_MID_PER_PAGE - 1) * P2M_PER_PAGE;

			continue;

		}



		if (mid_mfn_p == p2m_mid_missing_mfn) {

			/*

			 * XXX boot-time only!  We should never find

			 * missing parts of the mfn tree after

			 * runtime.  extend_brk() will BUG if we call

			 * it too late.

			 */

			mid_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE);

			p2m_mid_mfn_init(mid_mfn_p);



			p2m_top_mfn_p[topidx] = mid_mfn_p;

		}



		p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p);

		mid_mfn_p[mididx] = virt_to_mfn(mid[mididx]);

	}

}



void xen_setup_mfn_list_list(void)

{

	BUG_ON(HYPERVISOR_shared_info == &xen_dummy_shared_info);



	HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list =

		virt_to_mfn(p2m_top_mfn);

	HYPERVISOR_shared_info->arch.max_pfn = xen_max_p2m_pfn;

}



/* Set up p2m_top to point to the domain-builder provided p2m pages */

void __init xen_build_dynamic_phys_to_machine(void)

{

	unsigned long *mfn_list = (unsigned long *)xen_start_info->mfn_list;

	unsigned long max_pfn = min(MAX_DOMAIN_PAGES, xen_start_info->nr_pages);

	unsigned long pfn;



	xen_max_p2m_pfn = max_pfn;



	p2m_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);

	p2m_init(p2m_missing);



	p2m_mid_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);

	p2m_mid_init(p2m_mid_missing);



	p2m_top = extend_brk(PAGE_SIZE, PAGE_SIZE);

	p2m_top_init(p2m_top);



	/*

	 * The domain builder gives us a pre-constructed p2m array in

	 * mfn_list for all the pages initially given to us, so we just

	 * need to graft that into our tree structure.

	 */

	for (pfn = 0; pfn < max_pfn; pfn += P2M_PER_PAGE) {

		unsigned topidx = p2m_top_index(pfn);

		unsigned mididx = p2m_mid_index(pfn);



		if (p2m_top[topidx] == p2m_mid_missing) {

			unsigned long **mid = extend_brk(PAGE_SIZE, PAGE_SIZE);

			p2m_mid_init(mid);



			p2m_top[topidx] = mid;

		}



		p2m_top[topidx][mididx] = &mfn_list[pfn];

	}

}



unsigned long get_phys_to_machine(unsigned long pfn)

{

	unsigned topidx, mididx, idx;



	if (unlikely(pfn >= MAX_P2M_PFN))

		return INVALID_P2M_ENTRY;



	topidx = p2m_top_index(pfn);

	mididx = p2m_mid_index(pfn);

	idx = p2m_index(pfn);



	return p2m_top[topidx][mididx][idx];

}

EXPORT_SYMBOL_GPL(get_phys_to_machine);



static void *alloc_p2m_page(void)

{

	return (void *)__get_free_page(GFP_KERNEL | __GFP_REPEAT);

}



static void free_p2m_page(void *p)

{

	free_page((unsigned long)p);

}



/* 

 * Fully allocate the p2m structure for a given pfn.  We need to check

 * that both the top and mid levels are allocated, and make sure the

 * parallel mfn tree is kept in sync.  We may race with other cpus, so

 * the new pages are installed with cmpxchg; if we lose the race then

 * simply free the page we allocated and use the one that's there.

 */

static bool alloc_p2m(unsigned long pfn)

{

	unsigned topidx, mididx;

	unsigned long ***top_p, **mid;

	unsigned long *top_mfn_p, *mid_mfn;



	topidx = p2m_top_index(pfn);

	mididx = p2m_mid_index(pfn);



	top_p = &p2m_top[topidx];

	mid = *top_p;



	if (mid == p2m_mid_missing) {

		/* Mid level is missing, allocate a new one */

		mid = alloc_p2m_page();

		if (!mid)

			return false;



		p2m_mid_init(mid);



		if (cmpxchg(top_p, p2m_mid_missing, mid) != p2m_mid_missing)

			free_p2m_page(mid);

	}



	top_mfn_p = &p2m_top_mfn[topidx];

	mid_mfn = p2m_top_mfn_p[topidx];



	BUG_ON(virt_to_mfn(mid_mfn) != *top_mfn_p);



	if (mid_mfn == p2m_mid_missing_mfn) {

		/* Separately check the mid mfn level */

		unsigned long missing_mfn;

		unsigned long mid_mfn_mfn;



		mid_mfn = alloc_p2m_page();

		if (!mid_mfn)

			return false;



		p2m_mid_mfn_init(mid_mfn);



		missing_mfn = virt_to_mfn(p2m_mid_missing_mfn);

		mid_mfn_mfn = virt_to_mfn(mid_mfn);

		if (cmpxchg(top_mfn_p, missing_mfn, mid_mfn_mfn) != missing_mfn)

			free_p2m_page(mid_mfn);

		else

			p2m_top_mfn_p[topidx] = mid_mfn;

	}



	if (p2m_top[topidx][mididx] == p2m_missing) {

		/* p2m leaf page is missing */

		unsigned long *p2m;



		p2m = alloc_p2m_page();

		if (!p2m)

			return false;



		p2m_init(p2m);



		if (cmpxchg(&mid[mididx], p2m_missing, p2m) != p2m_missing)

			free_p2m_page(p2m);

		else

			mid_mfn[mididx] = virt_to_mfn(p2m);

	}



	return true;

}



/* Try to install p2m mapping; fail if intermediate bits missing */

bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)

{

	unsigned topidx, mididx, idx;



	if (unlikely(pfn >= MAX_P2M_PFN)) {

		BUG_ON(mfn != INVALID_P2M_ENTRY);

		return true;

	}



	topidx = p2m_top_index(pfn);

	mididx = p2m_mid_index(pfn);

	idx = p2m_index(pfn);



	if (p2m_top[topidx][mididx] == p2m_missing)

		return mfn == INVALID_P2M_ENTRY;



	p2m_top[topidx][mididx][idx] = mfn;



	return true;

}



bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)

{

	if (unlikely(xen_feature(XENFEAT_auto_translated_physmap))) {

		BUG_ON(pfn != mfn && mfn != INVALID_P2M_ENTRY);

		return true;

	}



	if (unlikely(!__set_phys_to_machine(pfn, mfn)))  {

		if (!alloc_p2m(pfn))

			return false;



		if (!__set_phys_to_machine(pfn, mfn))

			return false;

	}



	return true;

}



unsigned long arbitrary_virt_to_mfn(void *vaddr)

{

	xmaddr_t maddr = arbitrary_virt_to_machine(vaddr);

arch/x86/xen/p2m.c

0 → 100644
+376 −0
Original line number Diff line number Diff line 
/*

 * Xen leaves the responsibility for maintaining p2m mappings to the

 * guests themselves, but it must also access and update the p2m array

 * during suspend/resume when all the pages are reallocated.

 *

 * The p2m table is logically a flat array, but we implement it as a

 * three-level tree to allow the address space to be sparse.

 *

 *                               Xen

 *                                |

 *     p2m_top              p2m_top_mfn

 *       /  \                   /   \

 * p2m_mid p2m_mid	p2m_mid_mfn p2m_mid_mfn

 *    / \      / \         /           /

 *  p2m p2m p2m p2m p2m p2m p2m ...

 *

 * The p2m_mid_mfn pages are mapped by p2m_top_mfn_p.

 *

 * The p2m_top and p2m_top_mfn levels are limited to 1 page, so the

 * maximum representable pseudo-physical address space is:

 *  P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE pages

 *

 * P2M_PER_PAGE depends on the architecture, as a mfn is always

 * unsigned long (8 bytes on 64-bit, 4 bytes on 32), leading to

 * 512 and 1024 entries respectively. 

 */



#include <linux/init.h>

#include <linux/module.h>



#include <asm/cache.h>

#include <asm/setup.h>



#include <asm/xen/page.h>

#include <asm/xen/hypercall.h>

#include <asm/xen/hypervisor.h>



#include "xen-ops.h"



unsigned long xen_max_p2m_pfn __read_mostly;



#define P2M_PER_PAGE		(PAGE_SIZE / sizeof(unsigned long))

#define P2M_MID_PER_PAGE	(PAGE_SIZE / sizeof(unsigned long *))

#define P2M_TOP_PER_PAGE	(PAGE_SIZE / sizeof(unsigned long **))



#define MAX_P2M_PFN		(P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE)



/* Placeholders for holes in the address space */

static RESERVE_BRK_ARRAY(unsigned long, p2m_missing, P2M_PER_PAGE);

static RESERVE_BRK_ARRAY(unsigned long *, p2m_mid_missing, P2M_MID_PER_PAGE);

static RESERVE_BRK_ARRAY(unsigned long, p2m_mid_missing_mfn, P2M_MID_PER_PAGE);



static RESERVE_BRK_ARRAY(unsigned long **, p2m_top, P2M_TOP_PER_PAGE);

static RESERVE_BRK_ARRAY(unsigned long, p2m_top_mfn, P2M_TOP_PER_PAGE);

static RESERVE_BRK_ARRAY(unsigned long *, p2m_top_mfn_p, P2M_TOP_PER_PAGE);



RESERVE_BRK(p2m_mid, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID_PER_PAGE)));

RESERVE_BRK(p2m_mid_mfn, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID_PER_PAGE)));



static inline unsigned p2m_top_index(unsigned long pfn)

{

	BUG_ON(pfn >= MAX_P2M_PFN);

	return pfn / (P2M_MID_PER_PAGE * P2M_PER_PAGE);

}



static inline unsigned p2m_mid_index(unsigned long pfn)

{

	return (pfn / P2M_PER_PAGE) % P2M_MID_PER_PAGE;

}



static inline unsigned p2m_index(unsigned long pfn)

{

	return pfn % P2M_PER_PAGE;

}



static void p2m_top_init(unsigned long ***top)

{

	unsigned i;



	for (i = 0; i < P2M_TOP_PER_PAGE; i++)

		top[i] = p2m_mid_missing;

}



static void p2m_top_mfn_init(unsigned long *top)

{

	unsigned i;



	for (i = 0; i < P2M_TOP_PER_PAGE; i++)

		top[i] = virt_to_mfn(p2m_mid_missing_mfn);

}



static void p2m_top_mfn_p_init(unsigned long **top)

{

	unsigned i;



	for (i = 0; i < P2M_TOP_PER_PAGE; i++)

		top[i] = p2m_mid_missing_mfn;

}



static void p2m_mid_init(unsigned long **mid)

{

	unsigned i;



	for (i = 0; i < P2M_MID_PER_PAGE; i++)

		mid[i] = p2m_missing;

}



static void p2m_mid_mfn_init(unsigned long *mid)

{

	unsigned i;



	for (i = 0; i < P2M_MID_PER_PAGE; i++)

		mid[i] = virt_to_mfn(p2m_missing);

}



static void p2m_init(unsigned long *p2m)

{

	unsigned i;



	for (i = 0; i < P2M_MID_PER_PAGE; i++)

		p2m[i] = INVALID_P2M_ENTRY;

}



/*

 * Build the parallel p2m_top_mfn and p2m_mid_mfn structures

 *

 * This is called both at boot time, and after resuming from suspend:

 * - At boot time we're called very early, and must use extend_brk()

 *   to allocate memory.

 *

 * - After resume we're called from within stop_machine, but the mfn

 *   tree should alreay be completely allocated.

 */

void xen_build_mfn_list_list(void)

{

	unsigned long pfn;



	/* Pre-initialize p2m_top_mfn to be completely missing */

	if (p2m_top_mfn == NULL) {

		p2m_mid_missing_mfn = extend_brk(PAGE_SIZE, PAGE_SIZE);

		p2m_mid_mfn_init(p2m_mid_missing_mfn);



		p2m_top_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE);

		p2m_top_mfn_p_init(p2m_top_mfn_p);



		p2m_top_mfn = extend_brk(PAGE_SIZE, PAGE_SIZE);

		p2m_top_mfn_init(p2m_top_mfn);

	} else {

		/* Reinitialise, mfn's all change after migration */

		p2m_mid_mfn_init(p2m_mid_missing_mfn);

	}



	for (pfn = 0; pfn < xen_max_p2m_pfn; pfn += P2M_PER_PAGE) {

		unsigned topidx = p2m_top_index(pfn);

		unsigned mididx = p2m_mid_index(pfn);

		unsigned long **mid;

		unsigned long *mid_mfn_p;



		mid = p2m_top[topidx];

		mid_mfn_p = p2m_top_mfn_p[topidx];



		/* Don't bother allocating any mfn mid levels if

		 * they're just missing, just update the stored mfn,

		 * since all could have changed over a migrate.

		 */

		if (mid == p2m_mid_missing) {

			BUG_ON(mididx);

			BUG_ON(mid_mfn_p != p2m_mid_missing_mfn);

			p2m_top_mfn[topidx] = virt_to_mfn(p2m_mid_missing_mfn);

			pfn += (P2M_MID_PER_PAGE - 1) * P2M_PER_PAGE;

			continue;

		}



		if (mid_mfn_p == p2m_mid_missing_mfn) {

			/*

			 * XXX boot-time only!  We should never find

			 * missing parts of the mfn tree after

			 * runtime.  extend_brk() will BUG if we call

			 * it too late.

			 */

			mid_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE);

			p2m_mid_mfn_init(mid_mfn_p);



			p2m_top_mfn_p[topidx] = mid_mfn_p;

		}



		p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p);

		mid_mfn_p[mididx] = virt_to_mfn(mid[mididx]);

	}

}



void xen_setup_mfn_list_list(void)

{

	BUG_ON(HYPERVISOR_shared_info == &xen_dummy_shared_info);



	HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list =

		virt_to_mfn(p2m_top_mfn);

	HYPERVISOR_shared_info->arch.max_pfn = xen_max_p2m_pfn;

}



/* Set up p2m_top to point to the domain-builder provided p2m pages */

void __init xen_build_dynamic_phys_to_machine(void)

{

	unsigned long *mfn_list = (unsigned long *)xen_start_info->mfn_list;

	unsigned long max_pfn = min(MAX_DOMAIN_PAGES, xen_start_info->nr_pages);

	unsigned long pfn;



	xen_max_p2m_pfn = max_pfn;



	p2m_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);

	p2m_init(p2m_missing);



	p2m_mid_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);

	p2m_mid_init(p2m_mid_missing);



	p2m_top = extend_brk(PAGE_SIZE, PAGE_SIZE);

	p2m_top_init(p2m_top);



	/*

	 * The domain builder gives us a pre-constructed p2m array in

	 * mfn_list for all the pages initially given to us, so we just

	 * need to graft that into our tree structure.

	 */

	for (pfn = 0; pfn < max_pfn; pfn += P2M_PER_PAGE) {

		unsigned topidx = p2m_top_index(pfn);

		unsigned mididx = p2m_mid_index(pfn);



		if (p2m_top[topidx] == p2m_mid_missing) {

			unsigned long **mid = extend_brk(PAGE_SIZE, PAGE_SIZE);

			p2m_mid_init(mid);



			p2m_top[topidx] = mid;

		}



		p2m_top[topidx][mididx] = &mfn_list[pfn];

	}

}



unsigned long get_phys_to_machine(unsigned long pfn)

{

	unsigned topidx, mididx, idx;



	if (unlikely(pfn >= MAX_P2M_PFN))

		return INVALID_P2M_ENTRY;



	topidx = p2m_top_index(pfn);

	mididx = p2m_mid_index(pfn);

	idx = p2m_index(pfn);



	return p2m_top[topidx][mididx][idx];

}

EXPORT_SYMBOL_GPL(get_phys_to_machine);



static void *alloc_p2m_page(void)

{

	return (void *)__get_free_page(GFP_KERNEL | __GFP_REPEAT);

}



static void free_p2m_page(void *p)

{

	free_page((unsigned long)p);

}



/* 

 * Fully allocate the p2m structure for a given pfn.  We need to check

 * that both the top and mid levels are allocated, and make sure the

 * parallel mfn tree is kept in sync.  We may race with other cpus, so

 * the new pages are installed with cmpxchg; if we lose the race then

 * simply free the page we allocated and use the one that's there.

 */

static bool alloc_p2m(unsigned long pfn)

{

	unsigned topidx, mididx;

	unsigned long ***top_p, **mid;

	unsigned long *top_mfn_p, *mid_mfn;



	topidx = p2m_top_index(pfn);

	mididx = p2m_mid_index(pfn);



	top_p = &p2m_top[topidx];

	mid = *top_p;



	if (mid == p2m_mid_missing) {

		/* Mid level is missing, allocate a new one */

		mid = alloc_p2m_page();

		if (!mid)

			return false;



		p2m_mid_init(mid);



		if (cmpxchg(top_p, p2m_mid_missing, mid) != p2m_mid_missing)

			free_p2m_page(mid);

	}



	top_mfn_p = &p2m_top_mfn[topidx];

	mid_mfn = p2m_top_mfn_p[topidx];



	BUG_ON(virt_to_mfn(mid_mfn) != *top_mfn_p);



	if (mid_mfn == p2m_mid_missing_mfn) {

		/* Separately check the mid mfn level */

		unsigned long missing_mfn;

		unsigned long mid_mfn_mfn;



		mid_mfn = alloc_p2m_page();

		if (!mid_mfn)

			return false;



		p2m_mid_mfn_init(mid_mfn);



		missing_mfn = virt_to_mfn(p2m_mid_missing_mfn);

		mid_mfn_mfn = virt_to_mfn(mid_mfn);

		if (cmpxchg(top_mfn_p, missing_mfn, mid_mfn_mfn) != missing_mfn)

			free_p2m_page(mid_mfn);

		else

			p2m_top_mfn_p[topidx] = mid_mfn;

	}



	if (p2m_top[topidx][mididx] == p2m_missing) {

		/* p2m leaf page is missing */

		unsigned long *p2m;



		p2m = alloc_p2m_page();

		if (!p2m)

			return false;



		p2m_init(p2m);



		if (cmpxchg(&mid[mididx], p2m_missing, p2m) != p2m_missing)

			free_p2m_page(p2m);

		else

			mid_mfn[mididx] = virt_to_mfn(p2m);

	}



	return true;

}



/* Try to install p2m mapping; fail if intermediate bits missing */

bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)

{

	unsigned topidx, mididx, idx;



	if (unlikely(pfn >= MAX_P2M_PFN)) {

		BUG_ON(mfn != INVALID_P2M_ENTRY);

		return true;

	}



	topidx = p2m_top_index(pfn);

	mididx = p2m_mid_index(pfn);

	idx = p2m_index(pfn);



	if (p2m_top[topidx][mididx] == p2m_missing)

		return mfn == INVALID_P2M_ENTRY;



	p2m_top[topidx][mididx][idx] = mfn;



	return true;

}



bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)

{

	if (unlikely(xen_feature(XENFEAT_auto_translated_physmap))) {

		BUG_ON(pfn != mfn && mfn != INVALID_P2M_ENTRY);

		return true;

	}



	if (unlikely(!__set_phys_to_machine(pfn, mfn)))  {

		if (!alloc_p2m(pfn))

			return false;



		if (!__set_phys_to_machine(pfn, mfn))

			return false;

	}



	return true;

}