From: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
---
arch/x86/include/asm/xen/page.h | 16 ++++++-
arch/x86/xen/p2m.c | 80 +++++++++++++++++++++++++++++++++++++++
2 files changed, 93 insertions(+), 3 deletions(-)
diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
index 8760cc6..50f0a0f 100644
--- a/arch/x86/include/asm/xen/page.h
+++ b/arch/x86/include/asm/xen/page.h
@@ -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;
}
diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 259ec3b..8db19d5 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -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;
+}
--
1.5.6.5
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