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Message-ID: <20110222185527.22026.85401.stgit@s20.home>
Date: Tue, 22 Feb 2011 11:55:32 -0700
From: Alex Williamson <alex.williamson@...hat.com>
To: avi@...hat.com
Cc: alex.williamson@...hat.com, linux-kernel@...r.kernel.org,
kvm@...r.kernel.org, mtosatti@...hat.com,
xiaoguangrong@...fujitsu.com
Subject: [RFC PATCH 3/3] kvm: Use weight-balanced tree for memory slot
management
Rather than search linearly through an unordered slot array, we
can embed a tree node into each element. We can still do RCU
tree updates by applying the pointer offset to each element
in the new copy of the tree.
Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
---
include/linux/kvm_host.h | 3 +
virt/kvm/kvm_main.c | 163 +++++++++++++++++++++++++++++++++++++---------
2 files changed, 135 insertions(+), 31 deletions(-)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 7bbb36f..2a43f9b 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -18,6 +18,7 @@
#include <linux/msi.h>
#include <linux/slab.h>
#include <linux/rcupdate.h>
+#include <linux/wbtree.h>
#include <asm/signal.h>
#include <linux/kvm.h>
@@ -171,6 +172,7 @@ struct kvm_lpage_info {
};
struct kvm_memory_slot {
+ struct wb_node wb_node;
gfn_t base_gfn;
unsigned long npages;
unsigned long flags;
@@ -225,6 +227,7 @@ struct kvm_irq_routing_table {};
struct kvm_memslots {
int nmemslots;
u64 generation;
+ struct wb_root wb_root;
struct kvm_memory_slot memslots[];
};
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index a3a5bda..0a6ef96 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -447,6 +447,7 @@ static struct kvm *kvm_create_vm(void)
kvm->memslots = kzalloc(sizeof(struct kvm_memslots), GFP_KERNEL);
if (!kvm->memslots)
goto out_err_nosrcu;
+ kvm->memslots->wb_root = WB_ROOT;
if (init_srcu_struct(&kvm->srcu))
goto out_err_nosrcu;
for (i = 0; i < KVM_NR_BUSES; i++) {
@@ -611,6 +612,119 @@ static int kvm_create_dirty_bitmap(struct kvm_memory_slot *memslot)
}
#endif /* !CONFIG_S390 */
+static struct kvm_memory_slot *kvm_memslot_search(gfn_t gfn,
+ struct kvm_memslots *slots)
+{
+ struct wb_node *node = slots->wb_root.wb_node;
+ struct kvm_memory_slot *slot;
+
+ while (node) {
+ slot = wb_entry(node, struct kvm_memory_slot, wb_node);
+
+ if (gfn < slot->base_gfn)
+ node = node->wb_left;
+ else if (gfn >= slot->base_gfn + slot->npages)
+ node = node->wb_right;
+ else
+ return slot;
+ }
+ return NULL;
+}
+
+static void print_tree(struct kvm_memslots *slots)
+{
+ int i;
+
+ printk("digraph wbtree {\nnode [shape = record];\n");
+
+ for (i = 0; i < slots->nmemslots; i++) {
+ struct kvm_memory_slot *s = &slots->memslots[i];
+ struct wb_node *n = &s->wb_node;
+
+ if (!s->npages)
+ continue;
+
+ printk("node%d [label=\"<l> | <n> %lx-%lx\\n(%ld) | <r>\"];\n",
+ i, (unsigned long)s->base_gfn,
+ (unsigned long)(s->base_gfn + s->npages), s->npages);
+ if (n->wb_left) {
+ struct kvm_memory_slot *sl;
+ int left;
+ sl = wb_entry(n->wb_left, struct kvm_memory_slot,
+ wb_node);
+ left = sl - slots->memslots;
+ printk("\"node%d\":l -> \"node%d\":n;\n", i, left);
+ }
+ if (n->wb_right) {
+ struct kvm_memory_slot *sr;
+ int right;
+ sr = wb_entry(n->wb_right, struct kvm_memory_slot,
+ wb_node);
+ right = sr - slots->memslots;
+ printk("\"node%d\":r -> \"node%d\":n;\n", i, right);
+ }
+ }
+ printk("}\n");
+}
+
+static int kvm_memslot_insert(struct kvm_memory_slot *slot,
+ struct kvm_memslots *slots)
+{
+ struct wb_node **node = &slots->wb_root.wb_node, *parent = NULL;
+ struct kvm_memory_slot *memslot;
+
+ wb_set_weight(&slot->wb_node, slot->npages);
+
+ while (*node) {
+ memslot = wb_entry(*node, struct kvm_memory_slot, wb_node);
+ parent = *node;
+
+ if (slot->base_gfn + slot->npages <= memslot->base_gfn)
+ node = &(*node)->wb_left;
+ else if (slot->base_gfn >= memslot->base_gfn + memslot->npages)
+ node = &(*node)->wb_right;
+ else
+ return -EINVAL;
+ }
+
+ wb_link_node(&slot->wb_node, parent, node);
+ wb_rebalance(&slot->wb_node, &slots->wb_root);
+ print_tree(slots);
+ return 0;
+}
+
+static void kvm_memslot_remove(struct kvm_memory_slot *slot,
+ struct kvm_memslots *slots)
+{
+ wb_erase(&slot->wb_node, &slots->wb_root);
+ print_tree(slots);
+}
+
+static inline void kvm_memslot_pointer_fix(void *old, void *new, void **ptr)
+{
+ if (*ptr) {
+ if (new > old)
+ *ptr += (new - old);
+ else
+ *ptr -= (old - new);
+ }
+}
+
+static void kvm_memslots_copy_fixup(struct kvm_memslots *old,
+ struct kvm_memslots *new)
+{
+ int i;
+
+ for (i = 0; i < old->nmemslots; i++) {
+ struct wb_node *node = &new->memslots[i].wb_node;
+ kvm_memslot_pointer_fix(old, new, (void **)&node->wb_left);
+ kvm_memslot_pointer_fix(old, new, (void **)&node->wb_right);
+ kvm_memslot_pointer_fix(old, new, (void **)&node->wb_parent);
+ }
+
+ kvm_memslot_pointer_fix(old, new, (void **)&new->wb_root.wb_node);
+}
+
/*
* Allocate some memory and give it an address in the guest physical address
* space.
@@ -767,6 +881,8 @@ skip_lpage:
memcpy(slots, kvm->memslots,
sizeof(struct kvm_memslots) + kvm->memslots->nmemslots *
sizeof(struct kvm_memory_slot));
+ kvm_memslots_copy_fixup(kvm->memslots, slots);
+ new.wb_node = slots->memslots[mem->slot].wb_node;
slots->nmemslots = nmemslots;
slots->generation++;
slots->memslots[mem->slot].flags |= KVM_MEMSLOT_INVALID;
@@ -823,6 +939,13 @@ skip_lpage:
}
slots->memslots[mem->slot] = new;
+ kvm_memslots_copy_fixup(kvm->memslots, slots);
+
+ if (npages)
+ kvm_memslot_insert(&slots->memslots[mem->slot], slots);
+ else
+ kvm_memslot_remove(&slots->memslots[mem->slot], slots);
+
old_memslots = kvm->memslots;
rcu_assign_pointer(kvm->memslots, slots);
synchronize_srcu_expedited(&kvm->srcu);
@@ -946,16 +1069,7 @@ EXPORT_SYMBOL_GPL(kvm_is_error_hva);
static struct kvm_memory_slot *__gfn_to_memslot(struct kvm_memslots *slots,
gfn_t gfn)
{
- int i;
-
- for (i = 0; i < slots->nmemslots; ++i) {
- struct kvm_memory_slot *memslot = &slots->memslots[i];
-
- if (gfn >= memslot->base_gfn
- && gfn < memslot->base_gfn + memslot->npages)
- return memslot;
- }
- return NULL;
+ return kvm_memslot_search(gfn, slots);
}
struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn)
@@ -966,20 +1080,16 @@ EXPORT_SYMBOL_GPL(gfn_to_memslot);
int kvm_is_visible_gfn(struct kvm *kvm, gfn_t gfn)
{
- int i;
struct kvm_memslots *slots = kvm_memslots(kvm);
+ struct kvm_memory_slot *slot = kvm_memslot_search(gfn, slots);
- for (i = KVM_PRIVATE_MEM_SLOTS; i < slots->nmemslots; ++i) {
- struct kvm_memory_slot *memslot = &slots->memslots[i];
+ if (!slot || slot->flags & KVM_MEMSLOT_INVALID)
+ return 0;
- if (memslot->flags & KVM_MEMSLOT_INVALID)
- continue;
+ if (slot - slots->memslots < KVM_PRIVATE_MEM_SLOTS)
+ return 0;
- if (gfn >= memslot->base_gfn
- && gfn < memslot->base_gfn + memslot->npages)
- return 1;
- }
- return 0;
+ return 1;
}
EXPORT_SYMBOL_GPL(kvm_is_visible_gfn);
@@ -1009,19 +1119,10 @@ out:
int memslot_id(struct kvm *kvm, gfn_t gfn)
{
- int i;
struct kvm_memslots *slots = kvm_memslots(kvm);
- struct kvm_memory_slot *memslot = NULL;
-
- for (i = 0; i < slots->nmemslots; ++i) {
- memslot = &slots->memslots[i];
-
- if (gfn >= memslot->base_gfn
- && gfn < memslot->base_gfn + memslot->npages)
- break;
- }
+ struct kvm_memory_slot *slot = kvm_memslot_search(gfn, slots);
- return memslot - slots->memslots;
+ return slot ? slot - slots->memslots : slots->nmemslots;
}
static unsigned long gfn_to_hva_many(struct kvm_memory_slot *slot, gfn_t gfn,
--
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