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Date: Thu, 4 Nov 2021 00:25:28 +0000
From: Sean Christopherson <seanjc@...gle.com>
To: Marc Zyngier <maz@...nel.org>, Huacai Chen <chenhuacai@...nel.org>,
Aleksandar Markovic <aleksandar.qemu.devel@...il.com>,
Paul Mackerras <paulus@...abs.org>,
Anup Patel <anup.patel@....com>,
Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>,
Christian Borntraeger <borntraeger@...ibm.com>,
Janosch Frank <frankja@...ux.ibm.com>,
Paolo Bonzini <pbonzini@...hat.com>
Cc: James Morse <james.morse@....com>,
Alexandru Elisei <alexandru.elisei@....com>,
Suzuki K Poulose <suzuki.poulose@....com>,
Atish Patra <atish.patra@....com>,
David Hildenbrand <david@...hat.com>,
Cornelia Huck <cohuck@...hat.com>,
Claudio Imbrenda <imbrenda@...ux.ibm.com>,
Sean Christopherson <seanjc@...gle.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>,
Joerg Roedel <joro@...tes.org>,
linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
linux-mips@...r.kernel.org, kvm@...r.kernel.org,
kvm-ppc@...r.kernel.org, kvm-riscv@...ts.infradead.org,
linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
Ben Gardon <bgardon@...gle.com>,
"Maciej S . Szmigiero" <maciej.szmigiero@...cle.com>
Subject: [PATCH v5.5 27/30] KVM: Optimize gfn lookup in kvm_zap_gfn_range()
From: Maciej S. Szmigiero <maciej.szmigiero@...cle.com>
Introduce a memslots gfn upper bound operation and use it to optimize
kvm_zap_gfn_range().
This way this handler can do a quick lookup for intersecting gfns and won't
have to do a linear scan of the whole memslot set.
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@...cle.com>
Not-signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
arch/x86/kvm/mmu/mmu.c | 11 +++++--
include/linux/kvm_host.h | 69 ++++++++++++++++++++++++++++++++++++++++
2 files changed, 78 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 09ff0ccaa203..14e41278c069 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -5714,16 +5714,20 @@ static bool __kvm_zap_rmaps(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end)
{
const struct kvm_memory_slot *memslot;
struct kvm_memslots *slots;
+ struct rb_node *node;
bool flush = false;
gfn_t start, end;
- int i, bkt;
+ int i, idx;
if (!kvm_memslots_have_rmaps(kvm))
return flush;
for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
slots = __kvm_memslots(kvm, i);
- kvm_for_each_memslot(memslot, bkt, slots) {
+ idx = slots->node_idx;
+
+ kvm_for_each_memslot_in_gfn_range(node, slots, gfn_start, gfn_end) {
+ memslot = container_of(node, struct kvm_memory_slot, gfn_node[idx]);
start = max(gfn_start, memslot->base_gfn);
end = min(gfn_end, memslot->base_gfn + memslot->npages);
if (start >= end)
@@ -5747,6 +5751,9 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end)
bool flush;
int i;
+ if (WARN_ON_ONCE(gfn_end <= gfn_start))
+ return;
+
write_lock(&kvm->mmu_lock);
kvm_inc_notifier_count(kvm, gfn_start, gfn_end);
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 6888f3c2e04b..810a5b958697 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -832,6 +832,75 @@ struct kvm_memory_slot *id_to_memslot(struct kvm_memslots *slots, int id)
return NULL;
}
+static inline
+struct rb_node *kvm_memslots_gfn_upper_bound(struct kvm_memslots *slots, gfn_t gfn)
+{
+ int idx = slots->node_idx;
+ struct rb_node *node, *result = NULL;
+
+ for (node = slots->gfn_tree.rb_node; node; ) {
+ struct kvm_memory_slot *slot;
+
+ slot = container_of(node, struct kvm_memory_slot, gfn_node[idx]);
+ if (gfn < slot->base_gfn) {
+ result = node;
+ node = node->rb_left;
+ } else
+ node = node->rb_right;
+ }
+
+ return result;
+}
+
+static inline
+struct rb_node *kvm_for_each_in_gfn_first(struct kvm_memslots *slots, gfn_t start)
+{
+ struct rb_node *node;
+
+ /*
+ * Find the slot with the lowest gfn that can possibly intersect with
+ * the range, so we'll ideally have slot start <= range start
+ */
+ node = kvm_memslots_gfn_upper_bound(slots, start);
+ if (node) {
+ struct rb_node *pnode;
+
+ /*
+ * A NULL previous node means that the very first slot
+ * already has a higher start gfn.
+ * In this case slot start > range start.
+ */
+ pnode = rb_prev(node);
+ if (pnode)
+ node = pnode;
+ } else {
+ /* a NULL node below means no slots */
+ node = rb_last(&slots->gfn_tree);
+ }
+
+ return node;
+}
+
+static inline
+bool kvm_for_each_in_gfn_no_more(struct kvm_memslots *slots, struct rb_node *node, gfn_t end)
+{
+ struct kvm_memory_slot *memslot;
+
+ memslot = container_of(node, struct kvm_memory_slot, gfn_node[slots->node_idx]);
+
+ /*
+ * If this slot starts beyond or at the end of the range so does
+ * every next one
+ */
+ return memslot->base_gfn >= end;
+}
+
+/* Iterate over each memslot *possibly* intersecting [start, end) range */
+#define kvm_for_each_memslot_in_gfn_range(node, slots, start, end) \
+ for (node = kvm_for_each_in_gfn_first(slots, start); \
+ node && !kvm_for_each_in_gfn_no_more(slots, node, end); \
+ node = rb_next(node)) \
+
/*
* KVM_SET_USER_MEMORY_REGION ioctl allows the following operations:
* - create a new memory slot
--
2.33.1.1089.g2158813163f-goog
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