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Subject[PATCH 32/36] KVM: MMU: use page array in unsync walk
Date
From: Marcelo Tosatti <mtosatti@redhat.com>

Instead of invoking the handler directly collect pages into
an array so the caller can work with it.

Simplifies TLB flush collapsing.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
---
arch/x86/include/asm/kvm_host.h | 2 +-
arch/x86/kvm/mmu.c | 195 ++++++++++++++++++++++++++++-----------
2 files changed, 141 insertions(+), 56 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index f58f7eb..93d0aed 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -200,7 +200,7 @@ struct kvm_mmu_page {
int multimapped; /* More than one parent_pte? */
int root_count; /* Currently serving as active root */
bool unsync;
- bool unsync_children;
+ unsigned int unsync_children;
union {
u64 *parent_pte; /* !multimapped */
struct hlist_head parent_ptes; /* multimapped, kvm_pte_chain */
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index dd20b19..7ce92f7 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -908,8 +908,9 @@ static void kvm_mmu_update_unsync_bitmap(u64 *spte)
struct kvm_mmu_page *sp = page_header(__pa(spte));

index = spte - sp->spt;
- __set_bit(index, sp->unsync_child_bitmap);
- sp->unsync_children = 1;
+ if (!__test_and_set_bit(index, sp->unsync_child_bitmap))
+ sp->unsync_children++;
+ WARN_ON(!sp->unsync_children);
}

static void kvm_mmu_update_parents_unsync(struct kvm_mmu_page *sp)
@@ -936,7 +937,6 @@ static void kvm_mmu_update_parents_unsync(struct kvm_mmu_page *sp)

static int unsync_walk_fn(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
{
- sp->unsync_children = 1;
kvm_mmu_update_parents_unsync(sp);
return 1;
}
@@ -967,18 +967,41 @@ static void nonpaging_invlpg(struct kvm_vcpu *vcpu, gva_t gva)
{
}

+#define KVM_PAGE_ARRAY_NR 16
+
+struct kvm_mmu_pages {
+ struct mmu_page_and_offset {
+ struct kvm_mmu_page *sp;
+ unsigned int idx;
+ } page[KVM_PAGE_ARRAY_NR];
+ unsigned int nr;
+};
+
#define for_each_unsync_children(bitmap, idx) \
for (idx = find_first_bit(bitmap, 512); \
idx < 512; \
idx = find_next_bit(bitmap, 512, idx+1))

-static int mmu_unsync_walk(struct kvm_mmu_page *sp,
- struct kvm_unsync_walk *walker)
+int mmu_pages_add(struct kvm_mmu_pages *pvec, struct kvm_mmu_page *sp,
+ int idx)
{
- int i, ret;
+ int i;

- if (!sp->unsync_children)
- return 0;
+ if (sp->unsync)
+ for (i=0; i < pvec->nr; i++)
+ if (pvec->page[i].sp == sp)
+ return 0;
+
+ pvec->page[pvec->nr].sp = sp;
+ pvec->page[pvec->nr].idx = idx;
+ pvec->nr++;
+ return (pvec->nr == KVM_PAGE_ARRAY_NR);
+}
+
+static int __mmu_unsync_walk(struct kvm_mmu_page *sp,
+ struct kvm_mmu_pages *pvec)
+{
+ int i, ret, nr_unsync_leaf = 0;

for_each_unsync_children(sp->unsync_child_bitmap, i) {
u64 ent = sp->spt[i];
@@ -988,17 +1011,22 @@ static int mmu_unsync_walk(struct kvm_mmu_page *sp,
child = page_header(ent & PT64_BASE_ADDR_MASK);

if (child->unsync_children) {
- ret = mmu_unsync_walk(child, walker);
- if (ret)
+ if (mmu_pages_add(pvec, child, i))
+ return -ENOSPC;
+
+ ret = __mmu_unsync_walk(child, pvec);
+ if (!ret)
+ __clear_bit(i, sp->unsync_child_bitmap);
+ else if (ret > 0)
+ nr_unsync_leaf += ret;
+ else
return ret;
- __clear_bit(i, sp->unsync_child_bitmap);
}

if (child->unsync) {
- ret = walker->entry(child, walker);
- __clear_bit(i, sp->unsync_child_bitmap);
- if (ret)
- return ret;
+ nr_unsync_leaf++;
+ if (mmu_pages_add(pvec, child, i))
+ return -ENOSPC;
}
}
}
@@ -1006,7 +1034,17 @@ static int mmu_unsync_walk(struct kvm_mmu_page *sp,
if (find_first_bit(sp->unsync_child_bitmap, 512) == 512)
sp->unsync_children = 0;

- return 0;
+ return nr_unsync_leaf;
+}
+
+static int mmu_unsync_walk(struct kvm_mmu_page *sp,
+ struct kvm_mmu_pages *pvec)
+{
+ if (!sp->unsync_children)
+ return 0;
+
+ mmu_pages_add(pvec, sp, 0);
+ return __mmu_unsync_walk(sp, pvec);
}

static struct kvm_mmu_page *kvm_mmu_lookup_page(struct kvm *kvm, gfn_t gfn)
@@ -1056,30 +1094,81 @@ static int kvm_sync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
return 0;
}

-struct sync_walker {
- struct kvm_vcpu *vcpu;
- struct kvm_unsync_walk walker;
+struct mmu_page_path {
+ struct kvm_mmu_page *parent[PT64_ROOT_LEVEL-1];
+ unsigned int idx[PT64_ROOT_LEVEL-1];
};

-static int mmu_sync_fn(struct kvm_mmu_page *sp, struct kvm_unsync_walk *walk)
+#define for_each_sp(pvec, sp, parents, i) \
+ for (i = mmu_pages_next(&pvec, &parents, -1), \
+ sp = pvec.page[i].sp; \
+ i < pvec.nr && ({ sp = pvec.page[i].sp; 1;}); \
+ i = mmu_pages_next(&pvec, &parents, i))
+
+int mmu_pages_next(struct kvm_mmu_pages *pvec, struct mmu_page_path *parents,
+ int i)
{
- struct sync_walker *sync_walk = container_of(walk, struct sync_walker,
- walker);
- struct kvm_vcpu *vcpu = sync_walk->vcpu;
+ int n;
+
+ for (n = i+1; n < pvec->nr; n++) {
+ struct kvm_mmu_page *sp = pvec->page[n].sp;
+
+ if (sp->role.level == PT_PAGE_TABLE_LEVEL) {
+ parents->idx[0] = pvec->page[n].idx;
+ return n;
+ }

- kvm_sync_page(vcpu, sp);
- return (need_resched() || spin_needbreak(&vcpu->kvm->mmu_lock));
+ parents->parent[sp->role.level-2] = sp;
+ parents->idx[sp->role.level-1] = pvec->page[n].idx;
+ }
+
+ return n;
}

-static void mmu_sync_children(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
+void mmu_pages_clear_parents(struct mmu_page_path *parents)
{
- struct sync_walker walker = {
- .walker = { .entry = mmu_sync_fn, },
- .vcpu = vcpu,
- };
+ struct kvm_mmu_page *sp;
+ unsigned int level = 0;
+
+ do {
+ unsigned int idx = parents->idx[level];
+
+ sp = parents->parent[level];
+ if (!sp)
+ return;
+
+ --sp->unsync_children;
+ WARN_ON((int)sp->unsync_children < 0);
+ __clear_bit(idx, sp->unsync_child_bitmap);
+ level++;
+ } while (level < PT64_ROOT_LEVEL-1 && !sp->unsync_children);
+}
+
+static void kvm_mmu_pages_init(struct kvm_mmu_page *parent,
+ struct mmu_page_path *parents,
+ struct kvm_mmu_pages *pvec)
+{
+ parents->parent[parent->role.level-1] = NULL;
+ pvec->nr = 0;
+}

- while (mmu_unsync_walk(sp, &walker.walker))
+static void mmu_sync_children(struct kvm_vcpu *vcpu,
+ struct kvm_mmu_page *parent)
+{
+ int i;
+ struct kvm_mmu_page *sp;
+ struct mmu_page_path parents;
+ struct kvm_mmu_pages pages;
+
+ kvm_mmu_pages_init(parent, &parents, &pages);
+ while (mmu_unsync_walk(parent, &pages)) {
+ for_each_sp(pages, sp, parents, i) {
+ kvm_sync_page(vcpu, sp);
+ mmu_pages_clear_parents(&parents);
+ }
cond_resched_lock(&vcpu->kvm->mmu_lock);
+ kvm_mmu_pages_init(parent, &parents, &pages);
+ }
}

static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
@@ -1245,33 +1334,29 @@ static void kvm_mmu_unlink_parents(struct kvm *kvm, struct kvm_mmu_page *sp)
}
}

-struct zap_walker {
- struct kvm_unsync_walk walker;
- struct kvm *kvm;
- int zapped;
-};
-
-static int mmu_zap_fn(struct kvm_mmu_page *sp, struct kvm_unsync_walk *walk)
-{
- struct zap_walker *zap_walk = container_of(walk, struct zap_walker,
- walker);
- kvm_mmu_zap_page(zap_walk->kvm, sp);
- zap_walk->zapped = 1;
- return 0;
-}
-
-static int mmu_zap_unsync_children(struct kvm *kvm, struct kvm_mmu_page *sp)
+static int mmu_zap_unsync_children(struct kvm *kvm,
+ struct kvm_mmu_page *parent)
{
- struct zap_walker walker = {
- .walker = { .entry = mmu_zap_fn, },
- .kvm = kvm,
- .zapped = 0,
- };
+ int i, zapped = 0;
+ struct mmu_page_path parents;
+ struct kvm_mmu_pages pages;

- if (sp->role.level == PT_PAGE_TABLE_LEVEL)
+ if (parent->role.level == PT_PAGE_TABLE_LEVEL)
return 0;
- mmu_unsync_walk(sp, &walker.walker);
- return walker.zapped;
+
+ kvm_mmu_pages_init(parent, &parents, &pages);
+ while (mmu_unsync_walk(parent, &pages)) {
+ struct kvm_mmu_page *sp;
+
+ for_each_sp(pages, sp, parents, i) {
+ kvm_mmu_zap_page(kvm, sp);
+ mmu_pages_clear_parents(&parents);
+ }
+ zapped += pages.nr;
+ kvm_mmu_pages_init(parent, &parents, &pages);
+ }
+
+ return zapped;
}

static int kvm_mmu_zap_page(struct kvm *kvm, struct kvm_mmu_page *sp)
--
1.6.0.3


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