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xen: add m2p override mechanism

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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: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
Jeremy Fitzhardinge 2010-12-15 13:19:33 +00:00 committed by Konrad Rzeszutek Wilk
parent b5eafe924b
commit 448f283193
2 changed files with 93 additions and 3 deletions
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16
arch/x86/include/asm/xen/page.h
View File

@ -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;
}

80
arch/x86/xen/p2m.c
View File

@ -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;
}