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Commit 448f2831 authored by Jeremy Fitzhardinge's avatar Jeremy Fitzhardinge Committed by Konrad Rzeszutek Wilk
Browse files

xen: add m2p override mechanism 



Add a simple hashtable based mechanism to override some portions of the
m2p, so that we can find out the pfn corresponding to an mfn of a
granted page. In fact entries corresponding to granted pages in the m2p
hold the original pfn value of the page in the source domain that
granted it.

Signed-off-by: default avatarJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: default avatarStefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent b5eafe92

arch/x86/include/asm/xen/page.h

+13 −3
Original line number Diff line number Diff line
@@ -42,6 +42,11 @@ extern unsigned int machine_to_phys_order; 
extern unsigned long get_phys_to_machine(unsigned long pfn);

extern bool set_phys_to_machine(unsigned long pfn, unsigned long mfn);



extern void m2p_add_override(unsigned long mfn, struct page *page);

extern void m2p_remove_override(struct page *page);

extern struct page *m2p_find_override(unsigned long mfn);

extern unsigned long m2p_find_override_pfn(unsigned long mfn, unsigned long pfn);



static inline unsigned long pfn_to_mfn(unsigned long pfn)

{

	unsigned long mfn;
@@ -72,9 +77,6 @@ static inline unsigned long mfn_to_pfn(unsigned long mfn) 
	if (xen_feature(XENFEAT_auto_translated_physmap))

		return mfn;



	if (unlikely((mfn >> machine_to_phys_order) != 0))

		return ~0;



	pfn = 0;

	/*

	 * The array access can fail (e.g., device space beyond end of RAM).
@@ -83,6 +85,14 @@ static inline unsigned long mfn_to_pfn(unsigned long mfn) 
	 */

	__get_user(pfn, &machine_to_phys_mapping[mfn]);



	/*

	 * If this appears to be a foreign mfn (because the pfn

	 * doesn't map back to the mfn), then check the local override

	 * table to see if there's a better pfn to use.

	 */

	if (get_phys_to_machine(pfn) != mfn)

		pfn = m2p_find_override_pfn(mfn, pfn);



	return pfn;

}

arch/x86/xen/p2m.c

+80 −0
Original line number Diff line number Diff line
@@ -27,6 +27,8 @@ 


#include <linux/init.h>

#include <linux/module.h>

#include <linux/list.h>

#include <linux/hash.h>



#include <asm/cache.h>

#include <asm/setup.h>
@@ -37,6 +39,8 @@ 


#include "xen-ops.h"



static void __init m2p_override_init(void);



unsigned long xen_max_p2m_pfn __read_mostly;



#define P2M_PER_PAGE		(PAGE_SIZE / sizeof(unsigned long))
@@ -234,6 +238,8 @@ void __init xen_build_dynamic_phys_to_machine(void) 


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

	}



	m2p_override_init();

}



unsigned long get_phys_to_machine(unsigned long pfn)
@@ -374,3 +380,77 @@ bool set_phys_to_machine(unsigned long pfn, unsigned long mfn) 


	return true;

}



#define M2P_OVERRIDE_HASH_SHIFT	10

#define M2P_OVERRIDE_HASH	(1 << M2P_OVERRIDE_HASH_SHIFT)



static RESERVE_BRK_ARRAY(struct list_head, m2p_overrides, M2P_OVERRIDE_HASH);

static DEFINE_SPINLOCK(m2p_override_lock);



static void __init m2p_override_init(void)

{

	unsigned i;



	m2p_overrides = extend_brk(sizeof(*m2p_overrides) * M2P_OVERRIDE_HASH,

				   sizeof(unsigned long));



	for (i = 0; i < M2P_OVERRIDE_HASH; i++)

		INIT_LIST_HEAD(&m2p_overrides[i]);

}



static unsigned long mfn_hash(unsigned long mfn)

{

	return hash_long(mfn, M2P_OVERRIDE_HASH_SHIFT);

}



/* Add an MFN override for a particular page */

void m2p_add_override(unsigned long mfn, struct page *page)

{

	unsigned long flags;

	page->private = mfn;



	spin_lock_irqsave(&m2p_override_lock, flags);

	list_add(&page->lru,  &m2p_overrides[mfn_hash(mfn)]);

	spin_unlock_irqrestore(&m2p_override_lock, flags);

}



void m2p_remove_override(struct page *page)

{

	unsigned long flags;

	spin_lock_irqsave(&m2p_override_lock, flags);

	list_del(&page->lru);

	spin_unlock_irqrestore(&m2p_override_lock, flags);

}



struct page *m2p_find_override(unsigned long mfn)

{

	unsigned long flags;

	struct list_head *bucket = &m2p_overrides[mfn_hash(mfn)];

	struct page *p, *ret;



	ret = NULL;



	spin_lock_irqsave(&m2p_override_lock, flags);



	list_for_each_entry(p, bucket, lru) {

		if (p->private == mfn) {

			ret = p;

			break;

		}

	}



	spin_unlock_irqrestore(&m2p_override_lock, flags);



	return ret;

}



unsigned long m2p_find_override_pfn(unsigned long mfn, unsigned long pfn)

{

	struct page *p = m2p_find_override(mfn);

	unsigned long ret = pfn;



	if (p)

		ret = page_to_pfn(p);



	return ret;

}