[PATCH 7/7] KVM: MMU: don't walk every parent pages while mark unsync

From: Xiao Guangrong
Date: Fri Jun 11 2010 - 09:38:54 EST


While we mark the parent's unsync_child_bitmap, if the parent is already
unsynced, it no need walk it's parent, it can reduce some unnecessary
workload

Signed-off-by: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxx>
---
arch/x86/kvm/mmu.c | 61 ++++++++++++++-------------------------------------
1 files changed, 17 insertions(+), 44 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index eb20682..a92863f 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -175,7 +175,7 @@ struct kvm_shadow_walk_iterator {
shadow_walk_okay(&(_walker)); \
shadow_walk_next(&(_walker)))

-typedef int (*mmu_parent_walk_fn) (struct kvm_mmu_page *sp);
+typedef void (*mmu_parent_walk_fn) (struct kvm_mmu_page *sp, u64 *spte);

static struct kmem_cache *pte_chain_cache;
static struct kmem_cache *rmap_desc_cache;
@@ -1024,7 +1024,6 @@ static void mmu_page_remove_parent_pte(struct kvm_mmu_page *sp,
BUG();
}

-
static void mmu_parent_walk(struct kvm_mmu_page *sp, mmu_parent_walk_fn fn)
{
struct kvm_pte_chain *pte_chain;
@@ -1034,63 +1033,37 @@ static void mmu_parent_walk(struct kvm_mmu_page *sp, mmu_parent_walk_fn fn)

if (!sp->multimapped && sp->parent_pte) {
parent_sp = page_header(__pa(sp->parent_pte));
- fn(parent_sp);
- mmu_parent_walk(parent_sp, fn);
+ fn(parent_sp, sp->parent_pte);
return;
}
+
hlist_for_each_entry(pte_chain, node, &sp->parent_ptes, link)
for (i = 0; i < NR_PTE_CHAIN_ENTRIES; ++i) {
- if (!pte_chain->parent_ptes[i])
+ u64 *spte = pte_chain->parent_ptes[i];
+
+ if (!spte)
break;
- parent_sp = page_header(__pa(pte_chain->parent_ptes[i]));
- fn(parent_sp);
- mmu_parent_walk(parent_sp, fn);
+ parent_sp = page_header(__pa(spte));
+ fn(parent_sp, spte);
}
}

-static void kvm_mmu_update_unsync_bitmap(u64 *spte)
+static void mark_unsync(struct kvm_mmu_page *sp, u64 *spte);
+static void kvm_mmu_mark_parents_unsync(struct kvm_mmu_page *sp)
{
- unsigned int index;
- struct kvm_mmu_page *sp = page_header(__pa(spte));
-
- index = spte - sp->spt;
- if (!__test_and_set_bit(index, sp->unsync_child_bitmap))
- sp->unsync_children++;
- WARN_ON(!sp->unsync_children);
+ mmu_parent_walk(sp, mark_unsync);
}

-static void kvm_mmu_update_parents_unsync(struct kvm_mmu_page *sp)
+static void mark_unsync(struct kvm_mmu_page *sp, u64 *spte)
{
- struct kvm_pte_chain *pte_chain;
- struct hlist_node *node;
- int i;
+ unsigned int index;

- if (!sp->parent_pte)
+ index = spte - sp->spt;
+ if (__test_and_set_bit(index, sp->unsync_child_bitmap))
return;
-
- if (!sp->multimapped) {
- kvm_mmu_update_unsync_bitmap(sp->parent_pte);
+ if (sp->unsync_children++)
return;
- }
-
- hlist_for_each_entry(pte_chain, node, &sp->parent_ptes, link)
- for (i = 0; i < NR_PTE_CHAIN_ENTRIES; ++i) {
- if (!pte_chain->parent_ptes[i])
- break;
- kvm_mmu_update_unsync_bitmap(pte_chain->parent_ptes[i]);
- }
-}
-
-static int unsync_walk_fn(struct kvm_mmu_page *sp)
-{
- kvm_mmu_update_parents_unsync(sp);
- return 1;
-}
-
-static void kvm_mmu_mark_parents_unsync(struct kvm_mmu_page *sp)
-{
- mmu_parent_walk(sp, unsync_walk_fn);
- kvm_mmu_update_parents_unsync(sp);
+ kvm_mmu_mark_parents_unsync(sp);
}

static void nonpaging_prefetch_page(struct kvm_vcpu *vcpu,
--
1.6.1.2


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