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Message-Id: <4e6962905b2fc003acabf8bbee3a0ec1d634966c.1637884349.git.maciej.szmigiero@oracle.com>
Date: Fri, 26 Nov 2021 01:31:09 +0100
From: "Maciej S. Szmigiero" <mail@...iej.szmigiero.name>
To: Paolo Bonzini <pbonzini@...hat.com>
Cc: 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>,
Igor Mammedov <imammedo@...hat.com>, kvm@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH 3/3] KVM: Make kvm_for_each_memslot_in_gfn_range() strict and use iterators
From: "Maciej S. Szmigiero" <maciej.szmigiero@...cle.com>
Make kvm_for_each_memslot_in_gfn_range() return only memslots at least
partially intersecting the requested range.
At the same time modify its implementation to use iterators.
This simplifies kvm_check_memslot_overlap() a bit.
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@...cle.com>
---
arch/x86/kvm/mmu/mmu.c | 11 ++---
include/linux/kvm_host.h | 104 +++++++++++++++++++++++++--------------
virt/kvm/kvm_main.c | 17 ++-----
3 files changed, 75 insertions(+), 57 deletions(-)
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 8f0035517450..009eb27d34d3 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -5715,23 +5715,22 @@ 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;
+ struct kvm_memslot_iter iter;
bool flush = false;
gfn_t start, end;
- int i, idx;
+ int i;
if (!kvm_memslots_have_rmaps(kvm))
return flush;
for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
slots = __kvm_memslots(kvm, i);
- 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]);
+ kvm_for_each_memslot_in_gfn_range(&iter, slots, gfn_start, gfn_end) {
+ memslot = kvm_memslot_iter_slot(&iter);
start = max(gfn_start, memslot->base_gfn);
end = min(gfn_end, memslot->base_gfn + memslot->npages);
- if (start >= end)
+ if (WARN_ON_ONCE(start >= end))
continue;
flush = slot_handle_level_range(kvm, memslot, kvm_zap_rmapp,
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 3932bb091099..580d9abd97c1 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -841,74 +841,104 @@ 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)
+/* Iterator used for walking memslots that overlap a gfn range. */
+struct kvm_memslot_iter {
+ struct kvm_memslots *slots;
+ gfn_t end;
+ struct rb_node *node;
+};
+
+static inline void kvm_memslot_iter_start(struct kvm_memslot_iter *iter,
+ struct kvm_memslots *slots,
+ gfn_t start, gfn_t end)
{
int idx = slots->node_idx;
- struct rb_node *node, *result = NULL;
+ struct rb_node *tmp;
+ struct kvm_memory_slot *slot;
- for (node = slots->gfn_tree.rb_node; node; ) {
- struct kvm_memory_slot *slot;
+ iter->slots = slots;
+ iter->end = end;
- 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;
+ /*
+ * Find the so called "upper bound" of a key - the first node that has
+ * its key strictly greater than the searched one (the start gfn in our case).
+ */
+ iter->node = NULL;
+ for (tmp = slots->gfn_tree.rb_node; tmp; ) {
+ slot = container_of(tmp, struct kvm_memory_slot, gfn_node[idx]);
+ if (start < slot->base_gfn) {
+ iter->node = tmp;
+ tmp = tmp->rb_left;
+ } else {
+ tmp = tmp->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;
-
+ if (iter->node) {
/*
* 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;
+ tmp = rb_prev(iter->node);
+ if (tmp)
+ iter->node = tmp;
} else {
/* a NULL node below means no slots */
- node = rb_last(&slots->gfn_tree);
+ iter->node = rb_last(&slots->gfn_tree);
}
- return node;
+ if (iter->node) {
+ /*
+ * It is possible in the slot start < range start case that the
+ * found slot ends before or at range start (slot end <= range start)
+ * and so it does not overlap the requested range.
+ *
+ * In such non-overlapping case the next slot (if it exists) will
+ * already have slot start > range start, otherwise the logic above
+ * would have found it instead of the current slot.
+ */
+ slot = container_of(iter->node, struct kvm_memory_slot, gfn_node[idx]);
+ if (slot->base_gfn + slot->npages <= start)
+ iter->node = rb_next(iter->node);
+ }
}
-static inline
-bool kvm_for_each_in_gfn_no_more(struct kvm_memslots *slots, struct rb_node *node, gfn_t end)
+static inline struct kvm_memory_slot *kvm_memslot_iter_slot(struct kvm_memslot_iter *iter)
+{
+ return container_of(iter->node, struct kvm_memory_slot, gfn_node[iter->slots->node_idx]);
+}
+
+static inline bool kvm_memslot_iter_is_valid(struct kvm_memslot_iter *iter)
{
struct kvm_memory_slot *memslot;
- memslot = container_of(node, struct kvm_memory_slot, gfn_node[slots->node_idx]);
+ if (!iter->node)
+ return false;
+
+ memslot = kvm_memslot_iter_slot(iter);
/*
* If this slot starts beyond or at the end of the range so does
* every next one
*/
- return memslot->base_gfn >= end;
+ return memslot->base_gfn < iter->end;
+}
+
+static inline void kvm_memslot_iter_next(struct kvm_memslot_iter *iter)
+{
+ iter->node = rb_next(iter->node);
}
-/* 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)) \
+/* Iterate over each memslot at least partially intersecting [start, end) range */
+#define kvm_for_each_memslot_in_gfn_range(iter, slots, start, end) \
+ for (kvm_memslot_iter_start(iter, slots, start, end); \
+ kvm_memslot_iter_is_valid(iter); \
+ kvm_memslot_iter_next(iter))
/*
* KVM_SET_USER_MEMORY_REGION ioctl allows the following operations:
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 367c1cba26d2..d6503b92b3cf 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1797,22 +1797,11 @@ static int kvm_set_memslot(struct kvm *kvm,
static bool kvm_check_memslot_overlap(struct kvm_memslots *slots, int id,
gfn_t start, gfn_t end)
{
- int idx = slots->node_idx;
- struct rb_node *node;
-
- kvm_for_each_memslot_in_gfn_range(node, slots, start, end) {
- struct kvm_memory_slot *cslot;
- gfn_t cend;
+ struct kvm_memslot_iter iter;
- cslot = container_of(node, struct kvm_memory_slot, gfn_node[idx]);
- cend = cslot->base_gfn + cslot->npages;
- if (cslot->id == id)
- continue;
-
- /* kvm_for_each_in_gfn_no_more() guarantees that cslot->base_gfn < nend */
- if (cend > start)
+ kvm_for_each_memslot_in_gfn_range(&iter, slots, start, end)
+ if (kvm_memslot_iter_slot(&iter)->id != id)
return true;
- }
return false;
}
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