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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-changelog] [xen-unstable] [XEN] Simplify the shadow hash table.
# HG changeset patch
# User Tim Deegan <Tim.Deegan@xxxxxxxxxxxxx>
# Node ID 7a38b70788a5551bcb71a6edea7a40708556c60b
# Parent 6f0d8434d23f819e935e85bcee3885ce7bc1abe0
[XEN] Simplify the shadow hash table.
Chain hash buckets through the shadow page_info structs instead
of in separately allocated structures. This lets us get rid of
some xenheap allocations and a domain_crash_synchronous() call.
Signed-off-by: Tim Deegan <Tim.Deegan@xxxxxxxxxxxxx>
---
xen/arch/x86/mm/shadow/common.c | 326 ++++++++++++---------------------------
xen/arch/x86/mm/shadow/private.h | 8
xen/include/asm-x86/domain.h | 4
xen/include/asm-x86/shadow.h | 18 --
4 files changed, 110 insertions(+), 246 deletions(-)
diff -r 6f0d8434d23f -r 7a38b70788a5 xen/arch/x86/mm/shadow/common.c
--- a/xen/arch/x86/mm/shadow/common.c Thu Nov 23 17:40:28 2006 +0000
+++ b/xen/arch/x86/mm/shadow/common.c Thu Nov 23 17:42:29 2006 +0000
@@ -1265,17 +1265,22 @@ unsigned int shadow_set_allocation(struc
}
/**************************************************************************/
-/* Hash table for storing the guest->shadow mappings */
+/* Hash table for storing the guest->shadow mappings.
+ * The table itself is an array of pointers to shadows; the shadows are then
+ * threaded on a singly-linked list of shadows with the same hash value */
+
+#define SHADOW_HASH_BUCKETS 251
+/* Other possibly useful primes are 509, 1021, 2039, 4093, 8191, 16381 */
/* Hash function that takes a gfn or mfn, plus another byte of type info */
typedef u32 key_t;
-static inline key_t sh_hash(unsigned long n, u8 t)
+static inline key_t sh_hash(unsigned long n, unsigned int t)
{
unsigned char *p = (unsigned char *)&n;
key_t k = t;
int i;
for ( i = 0; i < sizeof(n) ; i++ ) k = (u32)p[i] + (k<<6) + (k<<16) - k;
- return k;
+ return k % SHADOW_HASH_BUCKETS;
}
#if SHADOW_AUDIT & (SHADOW_AUDIT_HASH|SHADOW_AUDIT_HASH_FULL)
@@ -1285,58 +1290,50 @@ static void sh_hash_audit_bucket(struct
static void sh_hash_audit_bucket(struct domain *d, int bucket)
/* Audit one bucket of the hash table */
{
- struct shadow_hash_entry *e, *x;
- struct shadow_page_info *sp;
+ struct shadow_page_info *sp, *x;
if ( !(SHADOW_AUDIT_ENABLE) )
return;
- e = &d->arch.shadow.hash_table[bucket];
- if ( e->t == 0 ) return; /* Bucket is empty */
- while ( e )
- {
- /* Empty link? */
- BUG_ON( e->t == 0 );
- /* Bogus type? */
- BUG_ON( e->t > SH_type_max_shadow );
- /* Wrong bucket? */
- BUG_ON( sh_hash(e->n, e->t) % SHADOW_HASH_BUCKETS != bucket );
- /* Duplicate entry? */
- for ( x = e->next; x; x = x->next )
- BUG_ON( x->n == e->n && x->t == e->t );
- /* Bogus MFN? */
- BUG_ON( !valid_mfn(e->smfn) );
- sp = mfn_to_shadow_page(e->smfn);
+ sp = d->arch.shadow.hash_table[bucket];
+ while ( sp )
+ {
/* Not a shadow? */
BUG_ON( sp->mbz != 0 );
- /* Wrong kind of shadow? */
- BUG_ON( sp->type != e->t );
- /* Bad backlink? */
- BUG_ON( sp->backpointer != e->n );
- if ( e->t != SH_type_fl1_32_shadow
- && e->t != SH_type_fl1_pae_shadow
- && e->t != SH_type_fl1_64_shadow )
- {
- struct page_info *gpg = mfn_to_page(_mfn(e->n));
+ /* Bogus type? */
+ BUG_ON( sp->type == 0 );
+ BUG_ON( sp->type > SH_type_max_shadow );
+ /* Wrong bucket? */
+ BUG_ON( sh_hash(sp->backpointer, sp->type) != bucket );
+ /* Duplicate entry? */
+ for ( x = sp->next_shadow; x; x = x->next_shadow )
+ BUG_ON( x->backpointer == sp->backpointer && x->type == sp->type );
+ /* Follow the backpointer to the guest pagetable */
+ if ( sp->type != SH_type_fl1_32_shadow
+ && sp->type != SH_type_fl1_pae_shadow
+ && sp->type != SH_type_fl1_64_shadow )
+ {
+ struct page_info *gpg = mfn_to_page(_mfn(sp->backpointer));
/* Bad shadow flags on guest page? */
- BUG_ON( !(gpg->shadow_flags & (1<<e->t)) );
+ BUG_ON( !(gpg->shadow_flags & (1<<sp->type)) );
/* Bad type count on guest page? */
if ( (gpg->u.inuse.type_info & PGT_type_mask) == PGT_writable_page
&& (gpg->u.inuse.type_info & PGT_count_mask) != 0 )
{
- SHADOW_ERROR("MFN %#"SH_PRI_mfn" shadowed (by %#"SH_PRI_mfn")"
+ SHADOW_ERROR("MFN %#lx shadowed (by %#"SH_PRI_mfn")"
" but has typecount %#lx\n",
- e->n, mfn_x(e->smfn), gpg->u.inuse.type_info);
+ sp->backpointer, mfn_x(shadow_page_to_mfn(sp)),
+ gpg->u.inuse.type_info);
BUG();
}
}
/* That entry was OK; on we go */
- e = e->next;
+ sp = sp->next_shadow;
}
}
#else
-#define sh_hash_audit_bucket(_d, _b)
+#define sh_hash_audit_bucket(_d, _b) do {} while(0)
#endif /* Hashtable bucket audit */
@@ -1357,75 +1354,22 @@ static void sh_hash_audit(struct domain
}
#else
-#define sh_hash_audit(_d)
+#define sh_hash_audit(_d) do {} while(0)
#endif /* Hashtable bucket audit */
-
-/* Memory management interface for bucket allocation.
- * These ought to come out of shadow memory, but at least on 32-bit
- * machines we are forced to allocate them from xenheap so that we can
- * address them. */
-static struct shadow_hash_entry *sh_alloc_hash_entry(struct domain *d)
-{
- struct shadow_hash_entry *extra, *x;
- int i;
-
- /* We need to allocate a new node. Ensure the free list is not empty.
- * Allocate new entries in units the same size as the original table. */
- if ( unlikely(d->arch.shadow.hash_freelist == NULL) )
- {
- size_t sz = sizeof(void *) + (SHADOW_HASH_BUCKETS * sizeof(*x));
- extra = xmalloc_bytes(sz);
-
- if ( extra == NULL )
- {
- /* No memory left! */
- SHADOW_ERROR("xmalloc() failed when allocating hash buckets.\n");
- domain_crash_synchronous();
- }
- memset(extra, 0, sz);
-
- /* Record the allocation block so it can be correctly freed later. */
- *((struct shadow_hash_entry **)&extra[SHADOW_HASH_BUCKETS]) =
- d->arch.shadow.hash_allocations;
- d->arch.shadow.hash_allocations = &extra[0];
-
- /* Thread a free chain through the newly-allocated nodes. */
- for ( i = 0; i < (SHADOW_HASH_BUCKETS - 1); i++ )
- extra[i].next = &extra[i+1];
- extra[i].next = NULL;
-
- /* Add the new nodes to the free list. */
- d->arch.shadow.hash_freelist = &extra[0];
- }
-
- /* Allocate a new node from the free list. */
- x = d->arch.shadow.hash_freelist;
- d->arch.shadow.hash_freelist = x->next;
- return x;
-}
-
-static void sh_free_hash_entry(struct domain *d, struct shadow_hash_entry *e)
-{
- /* Mark the bucket as empty and return it to the free list */
- e->t = 0;
- e->next = d->arch.shadow.hash_freelist;
- d->arch.shadow.hash_freelist = e;
-}
-
/* Allocate and initialise the table itself.
* Returns 0 for success, 1 for error. */
static int shadow_hash_alloc(struct domain *d)
{
- struct shadow_hash_entry *table;
+ struct shadow_page_info **table;
ASSERT(shadow_lock_is_acquired(d));
ASSERT(!d->arch.shadow.hash_table);
- table = xmalloc_array(struct shadow_hash_entry, SHADOW_HASH_BUCKETS);
+ table = xmalloc_array(struct shadow_page_info *, SHADOW_HASH_BUCKETS);
if ( !table ) return 1;
memset(table, 0,
- SHADOW_HASH_BUCKETS * sizeof (struct shadow_hash_entry));
+ SHADOW_HASH_BUCKETS * sizeof (struct shadow_page_info *));
d->arch.shadow.hash_table = table;
return 0;
}
@@ -1434,35 +1378,20 @@ static int shadow_hash_alloc(struct doma
* This function does not care whether the table is populated. */
static void shadow_hash_teardown(struct domain *d)
{
- struct shadow_hash_entry *a, *n;
-
ASSERT(shadow_lock_is_acquired(d));
ASSERT(d->arch.shadow.hash_table);
- /* Return the table itself */
xfree(d->arch.shadow.hash_table);
d->arch.shadow.hash_table = NULL;
-
- /* Return any extra allocations */
- a = d->arch.shadow.hash_allocations;
- while ( a )
- {
- /* We stored a linked-list pointer at the end of each allocation */
- n = *((struct shadow_hash_entry **)(&a[SHADOW_HASH_BUCKETS]));
- xfree(a);
- a = n;
- }
- d->arch.shadow.hash_allocations = NULL;
- d->arch.shadow.hash_freelist = NULL;
-}
-
-
-mfn_t shadow_hash_lookup(struct vcpu *v, unsigned long n, u8 t)
+}
+
+
+mfn_t shadow_hash_lookup(struct vcpu *v, unsigned long n, unsigned int t)
/* Find an entry in the hash table. Returns the MFN of the shadow,
* or INVALID_MFN if it doesn't exist */
{
struct domain *d = v->domain;
- struct shadow_hash_entry *p, *x, *head;
+ struct shadow_page_info *sp, *prev;
key_t key;
ASSERT(shadow_lock_is_acquired(d));
@@ -1473,58 +1402,50 @@ mfn_t shadow_hash_lookup(struct vcpu *v,
perfc_incrc(shadow_hash_lookups);
key = sh_hash(n, t);
-
- x = head = &d->arch.shadow.hash_table[key % SHADOW_HASH_BUCKETS];
- p = NULL;
-
- sh_hash_audit_bucket(d, key % SHADOW_HASH_BUCKETS);
-
- do
- {
- ASSERT(x->t || ((x == head) && (x->next == NULL)));
-
- if ( x->n == n && x->t == t )
- {
- /* Pull-to-front if 'x' isn't already the head item */
- if ( unlikely(x != head) )
+ sh_hash_audit_bucket(d, key);
+
+ sp = d->arch.shadow.hash_table[key];
+ prev = NULL;
+ while(sp)
+ {
+ if ( sp->backpointer == n && sp->type == t )
+ {
+ /* Pull-to-front if 'sp' isn't already the head item */
+ if ( unlikely(sp != d->arch.shadow.hash_table[key]) )
{
if ( unlikely(d->arch.shadow.hash_walking != 0) )
/* Can't reorder: someone is walking the hash chains */
- return x->smfn;
+ return shadow_page_to_mfn(sp);
else
{
- /* Delete 'x' from list and reinsert after head. */
- p->next = x->next;
- x->next = head->next;
- head->next = x;
-
- /* Swap 'x' contents with head contents. */
- SWAP(head->n, x->n);
- SWAP(head->t, x->t);
- SWAP(head->smfn, x->smfn);
+ ASSERT(prev);
+ /* Delete sp from the list */
+ prev->next_shadow = sp->next_shadow;
+ /* Re-insert it at the head of the list */
+ sp->next_shadow = d->arch.shadow.hash_table[key];
+ d->arch.shadow.hash_table[key] = sp;
}
}
else
{
perfc_incrc(shadow_hash_lookup_head);
}
- return head->smfn;
- }
-
- p = x;
- x = x->next;
- }
- while ( x != NULL );
+ return shadow_page_to_mfn(sp);
+ }
+ prev = sp;
+ sp = sp->next_shadow;
+ }
perfc_incrc(shadow_hash_lookup_miss);
return _mfn(INVALID_MFN);
}
-void shadow_hash_insert(struct vcpu *v, unsigned long n, u8 t, mfn_t smfn)
+void shadow_hash_insert(struct vcpu *v, unsigned long n, unsigned int t,
+ mfn_t smfn)
/* Put a mapping (n,t)->smfn into the hash table */
{
struct domain *d = v->domain;
- struct shadow_hash_entry *x, *head;
+ struct shadow_page_info *sp;
key_t key;
ASSERT(shadow_lock_is_acquired(d));
@@ -1535,38 +1456,22 @@ void shadow_hash_insert(struct vcpu *v,
perfc_incrc(shadow_hash_inserts);
key = sh_hash(n, t);
-
- head = &d->arch.shadow.hash_table[key % SHADOW_HASH_BUCKETS];
-
- sh_hash_audit_bucket(d, key % SHADOW_HASH_BUCKETS);
-
- /* If the bucket is empty then insert the new page as the head item. */
- if ( head->t == 0 )
- {
- head->n = n;
- head->t = t;
- head->smfn = smfn;
- ASSERT(head->next == NULL);
- }
- else
- {
- /* Insert a new entry directly after the head item. */
- x = sh_alloc_hash_entry(d);
- x->n = n;
- x->t = t;
- x->smfn = smfn;
- x->next = head->next;
- head->next = x;
- }
+ sh_hash_audit_bucket(d, key);
- sh_hash_audit_bucket(d, key % SHADOW_HASH_BUCKETS);
-}
-
-void shadow_hash_delete(struct vcpu *v, unsigned long n, u8 t, mfn_t smfn)
+ /* Insert this shadow at the top of the bucket */
+ sp = mfn_to_shadow_page(smfn);
+ sp->next_shadow = d->arch.shadow.hash_table[key];
+ d->arch.shadow.hash_table[key] = sp;
+
+ sh_hash_audit_bucket(d, key);
+}
+
+void shadow_hash_delete(struct vcpu *v, unsigned long n, unsigned int t,
+ mfn_t smfn)
/* Excise the mapping (n,t)->smfn from the hash table */
{
struct domain *d = v->domain;
- struct shadow_hash_entry *p, *x, *head;
+ struct shadow_page_info *sp, *x;
key_t key;
ASSERT(shadow_lock_is_acquired(d));
@@ -1577,54 +1482,31 @@ void shadow_hash_delete(struct vcpu *v,
perfc_incrc(shadow_hash_deletes);
key = sh_hash(n, t);
-
- head = &d->arch.shadow.hash_table[key % SHADOW_HASH_BUCKETS];
-
- sh_hash_audit_bucket(d, key % SHADOW_HASH_BUCKETS);
-
- /* Match on head item? */
- if ( head->n == n && head->t == t )
- {
- if ( (x = head->next) != NULL )
- {
- /* Overwrite head with contents of following node. */
- head->n = x->n;
- head->t = x->t;
- head->smfn = x->smfn;
-
- /* Delete following node. */
- head->next = x->next;
- sh_free_hash_entry(d, x);
- }
- else
- {
- /* This bucket is now empty. Initialise the head node. */
- head->t = 0;
- }
- }
+ sh_hash_audit_bucket(d, key);
+
+ sp = mfn_to_shadow_page(smfn);
+ if ( d->arch.shadow.hash_table[key] == sp )
+ /* Easy case: we're deleting the head item. */
+ d->arch.shadow.hash_table[key] = sp->next_shadow;
else
{
- /* Not at the head; need to walk the chain */
- p = head;
- x = head->next;
-
- while(1)
+ /* Need to search for the one we want */
+ x = d->arch.shadow.hash_table[key];
+ while ( 1 )
{
ASSERT(x); /* We can't have hit the end, since our target is
* still in the chain somehwere... */
- if ( x->n == n && x->t == t )
+ if ( x->next_shadow == sp )
{
- /* Delete matching node. */
- p->next = x->next;
- sh_free_hash_entry(d, x);
+ x->next_shadow = sp->next_shadow;
break;
}
- p = x;
- x = x->next;
- }
- }
-
- sh_hash_audit_bucket(d, key % SHADOW_HASH_BUCKETS);
+ x = x->next_shadow;
+ }
+ }
+ sp->next_shadow = NULL;
+
+ sh_hash_audit_bucket(d, key);
}
typedef int (*hash_callback_t)(struct vcpu *v, mfn_t smfn, mfn_t other_mfn);
@@ -1644,27 +1526,27 @@ static void hash_foreach(struct vcpu *v,
{
int i, done = 0;
struct domain *d = v->domain;
- struct shadow_hash_entry *x;
+ struct shadow_page_info *x;
/* Say we're here, to stop hash-lookups reordering the chains */
ASSERT(shadow_lock_is_acquired(d));
ASSERT(d->arch.shadow.hash_walking == 0);
d->arch.shadow.hash_walking = 1;
- callback_mask &= ~1; /* Never attempt to call back on empty buckets */
for ( i = 0; i < SHADOW_HASH_BUCKETS; i++ )
{
/* WARNING: This is not safe against changes to the hash table.
* The callback *must* return non-zero if it has inserted or
* deleted anything from the hash (lookups are OK, though). */
- for ( x = &d->arch.shadow.hash_table[i]; x; x = x->next )
- {
- if ( callback_mask & (1 << x->t) )
+ for ( x = d->arch.shadow.hash_table[i]; x; x = x->next_shadow )
+ {
+ if ( callback_mask & (1 << x->type) )
{
- ASSERT(x->t <= 15);
- ASSERT(callbacks[x->t] != NULL);
- if ( (done = callbacks[x->t](v, x->smfn, callback_mfn)) != 0 )
- break;
+ ASSERT(x->type <= 15);
+ ASSERT(callbacks[x->type] != NULL);
+ done = callbacks[x->type](v, shadow_page_to_mfn(x),
+ callback_mfn);
+ if ( done ) break;
}
}
if ( done ) break;
diff -r 6f0d8434d23f -r 7a38b70788a5 xen/arch/x86/mm/shadow/private.h
--- a/xen/arch/x86/mm/shadow/private.h Thu Nov 23 17:40:28 2006 +0000
+++ b/xen/arch/x86/mm/shadow/private.h Thu Nov 23 17:42:29 2006 +0000
@@ -229,9 +229,11 @@ extern struct x86_emulate_ops shadow_emu
extern struct x86_emulate_ops shadow_emulator_ops;
/* Hash table functions */
-mfn_t shadow_hash_lookup(struct vcpu *v, unsigned long n, u8 t);
-void shadow_hash_insert(struct vcpu *v, unsigned long n, u8 t, mfn_t smfn);
-void shadow_hash_delete(struct vcpu *v, unsigned long n, u8 t, mfn_t smfn);
+mfn_t shadow_hash_lookup(struct vcpu *v, unsigned long n, unsigned int t);
+void shadow_hash_insert(struct vcpu *v,
+ unsigned long n, unsigned int t, mfn_t smfn);
+void shadow_hash_delete(struct vcpu *v,
+ unsigned long n, unsigned int t, mfn_t smfn);
/* shadow promotion */
void shadow_promote(struct vcpu *v, mfn_t gmfn, u32 type);
diff -r 6f0d8434d23f -r 7a38b70788a5 xen/include/asm-x86/domain.h
--- a/xen/include/asm-x86/domain.h Thu Nov 23 17:40:28 2006 +0000
+++ b/xen/include/asm-x86/domain.h Thu Nov 23 17:42:29 2006 +0000
@@ -71,9 +71,7 @@ struct shadow_domain {
unsigned int p2m_pages; /* number of pages in p2m map */
/* Shadow hashtable */
- struct shadow_hash_entry *hash_table;
- struct shadow_hash_entry *hash_freelist;
- struct shadow_hash_entry *hash_allocations;
+ struct shadow_page_info **hash_table;
int hash_walking; /* Some function is walking the hash table */
/* Shadow log-dirty bitmap */
diff -r 6f0d8434d23f -r 7a38b70788a5 xen/include/asm-x86/shadow.h
--- a/xen/include/asm-x86/shadow.h Thu Nov 23 17:40:28 2006 +0000
+++ b/xen/include/asm-x86/shadow.h Thu Nov 23 17:42:29 2006 +0000
@@ -599,24 +599,6 @@ static inline unsigned int shadow_get_al
+ ((pg & ((1 << (20 - PAGE_SHIFT)) - 1)) ? 1 : 0));
}
-/*
- * Linked list for chaining entries in the shadow hash table.
- */
-struct shadow_hash_entry {
- struct shadow_hash_entry *next;
- mfn_t smfn; /* MFN of the shadow */
-#ifdef _x86_64_ /* Shorten 'n' so we don't waste a whole word on storing 't' */
- unsigned long n:56; /* MFN of guest PT or GFN of guest superpage */
-#else
- unsigned long n; /* MFN of guest PT or GFN of guest superpage */
-#endif
- unsigned char t; /* shadow type bits, or 0 for empty */
-};
-
-#define SHADOW_HASH_BUCKETS 251
-/* Other possibly useful primes are 509, 1021, 2039, 4093, 8191, 16381 */
-
-
#if SHADOW_OPTIMIZATIONS & SHOPT_CACHE_WALKS
/* Optimization: cache the results of guest walks. This helps with MMIO
* and emulated writes, which tend to issue very similar walk requests
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