[PATCH v5.5 24/30] KVM: Use interval tree to do fast hva lookup in memslots
Sean Christopherson
seanjc at google.com
Wed Nov 3 17:25:25 PDT 2021
From: Maciej S. Szmigiero <maciej.szmigiero at oracle.com>
The current memslots implementation only allows quick binary search by gfn,
quick lookup by hva is not possible - the implementation has to do a linear
scan of the whole memslots array, even though the operation being performed
might apply just to a single memslot.
This significantly hurts performance of per-hva operations with higher
memslot counts.
Since hva ranges can overlap between memslots an interval tree is needed
for tracking them.
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero at oracle.com>
[sean: handle interval tree updates in kvm_replace_memslot()]
Signed-off-by: Sean Christopherson <seanjc at google.com>
---
arch/arm64/kvm/Kconfig | 1 +
arch/mips/kvm/Kconfig | 1 +
arch/powerpc/kvm/Kconfig | 1 +
arch/s390/kvm/Kconfig | 1 +
arch/x86/kvm/Kconfig | 1 +
include/linux/kvm_host.h | 3 ++
virt/kvm/kvm_main.c | 60 +++++++++++++++++++++++++++++-----------
7 files changed, 52 insertions(+), 16 deletions(-)
diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
index d7eec0b43744..42185dcc9596 100644
--- a/arch/arm64/kvm/Kconfig
+++ b/arch/arm64/kvm/Kconfig
@@ -38,6 +38,7 @@ menuconfig KVM
select HAVE_KVM_IRQ_BYPASS
select HAVE_KVM_VCPU_RUN_PID_CHANGE
select SCHED_INFO
+ select INTERVAL_TREE
help
Support hosting virtualized guest machines.
diff --git a/arch/mips/kvm/Kconfig b/arch/mips/kvm/Kconfig
index a77297480f56..91d197bee9c0 100644
--- a/arch/mips/kvm/Kconfig
+++ b/arch/mips/kvm/Kconfig
@@ -27,6 +27,7 @@ config KVM
select KVM_MMIO
select MMU_NOTIFIER
select SRCU
+ select INTERVAL_TREE
help
Support for hosting Guest kernels.
diff --git a/arch/powerpc/kvm/Kconfig b/arch/powerpc/kvm/Kconfig
index ff581d70f20c..e4c24f524ba8 100644
--- a/arch/powerpc/kvm/Kconfig
+++ b/arch/powerpc/kvm/Kconfig
@@ -26,6 +26,7 @@ config KVM
select KVM_VFIO
select IRQ_BYPASS_MANAGER
select HAVE_KVM_IRQ_BYPASS
+ select INTERVAL_TREE
config KVM_BOOK3S_HANDLER
bool
diff --git a/arch/s390/kvm/Kconfig b/arch/s390/kvm/Kconfig
index 67a8e770e369..2e84d3922f7c 100644
--- a/arch/s390/kvm/Kconfig
+++ b/arch/s390/kvm/Kconfig
@@ -33,6 +33,7 @@ config KVM
select HAVE_KVM_NO_POLL
select SRCU
select KVM_VFIO
+ select INTERVAL_TREE
help
Support hosting paravirtualized guest machines using the SIE
virtualization capability on the mainframe. This should work
diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index 619186138176..7618bef0a4a9 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -43,6 +43,7 @@ config KVM
select KVM_GENERIC_DIRTYLOG_READ_PROTECT
select KVM_VFIO
select SRCU
+ select INTERVAL_TREE
select HAVE_KVM_PM_NOTIFIER if PM
help
Support hosting fully virtualized guest machines using hardware
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 81003e3acd53..d0363e2ba098 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -30,6 +30,7 @@
#include <linux/nospec.h>
#include <linux/notifier.h>
#include <linux/hashtable.h>
+#include <linux/interval_tree.h>
#include <asm/signal.h>
#include <linux/kvm.h>
@@ -427,6 +428,7 @@ static inline int kvm_vcpu_exiting_guest_mode(struct kvm_vcpu *vcpu)
struct kvm_memory_slot {
struct hlist_node id_node;
+ struct interval_tree_node hva_node;
gfn_t base_gfn;
unsigned long npages;
unsigned long *dirty_bitmap;
@@ -528,6 +530,7 @@ static inline int kvm_arch_vcpu_memslots_id(struct kvm_vcpu *vcpu)
*/
struct kvm_memslots {
u64 generation;
+ struct rb_root_cached hva_tree;
/* The mapping table from slot id to the index in memslots[]. */
DECLARE_HASHTABLE(id_hash, 7);
atomic_t last_used_slot;
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 13c497abaab8..f2235c430e64 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -498,6 +498,12 @@ static void kvm_null_fn(void)
}
#define IS_KVM_NULL_FN(fn) ((fn) == (void *)kvm_null_fn)
+/* Iterate over each memslot intersecting [start, last] (inclusive) range */
+#define kvm_for_each_memslot_in_hva_range(node, slots, start, last) \
+ for (node = interval_tree_iter_first(&slots->hva_tree, start, last); \
+ node; \
+ node = interval_tree_iter_next(node, start, last)) \
+
static __always_inline int __kvm_handle_hva_range(struct kvm *kvm,
const struct kvm_hva_range *range)
{
@@ -507,6 +513,9 @@ static __always_inline int __kvm_handle_hva_range(struct kvm *kvm,
struct kvm_memslots *slots;
int i, idx;
+ if (WARN_ON_ONCE(range->end <= range->start))
+ return 0;
+
/* A null handler is allowed if and only if on_lock() is provided. */
if (WARN_ON_ONCE(IS_KVM_NULL_FN(range->on_lock) &&
IS_KVM_NULL_FN(range->handler)))
@@ -515,15 +524,17 @@ static __always_inline int __kvm_handle_hva_range(struct kvm *kvm,
idx = srcu_read_lock(&kvm->srcu);
for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
+ struct interval_tree_node *node;
+
slots = __kvm_memslots(kvm, i);
- kvm_for_each_memslot(slot, slots) {
+ kvm_for_each_memslot_in_hva_range(node, slots,
+ range->start, range->end - 1) {
unsigned long hva_start, hva_end;
+ slot = container_of(node, struct kvm_memory_slot, hva_node);
hva_start = max(range->start, slot->userspace_addr);
hva_end = min(range->end, slot->userspace_addr +
(slot->npages << PAGE_SHIFT));
- if (hva_start >= hva_end)
- continue;
/*
* To optimize for the likely case where the address
@@ -859,6 +870,7 @@ static struct kvm_memslots *kvm_alloc_memslots(void)
if (!slots)
return NULL;
+ slots->hva_tree = RB_ROOT_CACHED;
hash_init(slots->id_hash);
return slots;
@@ -1262,22 +1274,32 @@ static void kvm_replace_memslot(struct kvm_memslots *slots,
struct kvm_memory_slot *new)
{
/*
- * Remove the old memslot from the hash list, copying the node data
- * would corrupt the list.
+ * Remove the old memslot from the hash list and interval tree, copying
+ * the node data would corrupt the structures.
*/
if (old) {
hash_del(&old->id_node);
+ interval_tree_remove(&old->hva_node, &slots->hva_tree);
if (!new)
return;
}
- /* Copy the source *data*, not the pointer, to the destination. */
- if (old)
+ /*
+ * Copy the source *data*, not the pointer, to the destination. If
+ * @old is NULL, initialize @new's hva range.
+ */
+ if (old) {
*new = *old;
+ } else if (new) {
+ new->hva_node.start = new->userspace_addr;
+ new->hva_node.last = new->userspace_addr +
+ (new->npages << PAGE_SHIFT) - 1;
+ }
/* (Re)Add the new memslot. */
hash_add(slots->id_hash, &new->id_node, new->id);
+ interval_tree_insert(&new->hva_node, &slots->hva_tree);
}
static void kvm_shift_memslot(struct kvm_memslots *slots, int dst, int src)
@@ -1308,7 +1330,7 @@ static inline void kvm_memslot_delete(struct kvm_memslots *slots,
atomic_set(&slots->last_used_slot, 0);
/*
- * Remove the to-be-deleted memslot from the list _before_ shifting
+ * Remove the to-be-deleted memslot from the list/tree _before_ shifting
* the trailing memslots forward, its data will be overwritten.
* Defer the (somewhat pointless) copying of the memslot until after
* the last slot has been shifted to avoid overwriting said last slot.
@@ -1335,7 +1357,8 @@ static inline int kvm_memslot_insert_back(struct kvm_memslots *slots)
* itself is not preserved in the array, i.e. not swapped at this time, only
* its new index into the array is tracked. Returns the changed memslot's
* current index into the memslots array.
- * The memslot at the returned index will not be in @slots->id_hash by then.
+ * The memslot at the returned index will not be in @slots->hva_tree or
+ * @slots->id_hash by then.
* @memslot is a detached struct with desired final data of the changed slot.
*/
static inline int kvm_memslot_move_backward(struct kvm_memslots *slots,
@@ -1349,10 +1372,10 @@ static inline int kvm_memslot_move_backward(struct kvm_memslots *slots,
return -1;
/*
- * Delete the slot from the hash table before sorting the remaining
- * slots, the slot's data may be overwritten when copying slots as part
- * of the sorting proccess. update_memslots() will unconditionally
- * rewrite the entire slot and re-add it to the hash table.
+ * Delete the slot from the hash table and interval tree before sorting
+ * the remaining slots, the slot's data may be overwritten when copying
+ * slots as part of the sorting proccess. update_memslots() will
+ * unconditionally rewrite and re-add the entire slot.
*/
kvm_replace_memslot(slots, oldslot, NULL);
@@ -1378,10 +1401,12 @@ static inline int kvm_memslot_move_backward(struct kvm_memslots *slots,
* is not preserved in the array, i.e. not swapped at this time, only its new
* index into the array is tracked. Returns the changed memslot's final index
* into the memslots array.
- * The memslot at the returned index will not be in @slots->id_hash by then.
+ * The memslot at the returned index will not be in @slots->hva_tree or
+ * @slots->id_hash by then.
* @memslot is a detached struct with desired final data of the new or
* changed slot.
- * Assumes that the memslot at @start index is not in @slots->id_hash.
+ * Assumes that the memslot at @start index is not in @slots->hva_tree or
+ * @slots->id_hash.
*/
static inline int kvm_memslot_move_forward(struct kvm_memslots *slots,
struct kvm_memory_slot *memslot,
@@ -1574,9 +1599,12 @@ static struct kvm_memslots *kvm_dup_memslots(struct kvm_memslots *old,
memcpy(slots, old, kvm_memslots_size(old->used_slots));
+ slots->hva_tree = RB_ROOT_CACHED;
hash_init(slots->id_hash);
- kvm_for_each_memslot(memslot, slots)
+ kvm_for_each_memslot(memslot, slots) {
+ interval_tree_insert(&memslot->hva_node, &slots->hva_tree);
hash_add(slots->id_hash, &memslot->id_node, memslot->id);
+ }
return slots;
}
--
2.33.1.1089.g2158813163f-goog
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