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Message-Id: <20210105233136.2140335-3-bgardon@google.com>
Date: Tue, 5 Jan 2021 15:31:36 -0800
From: Ben Gardon <bgardon@...gle.com>
To: linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc: Paolo Bonzini <pbonzini@...hat.com>,
Sean Christopherson <sean.j.christopherson@...el.com>,
Peter Shier <pshier@...gle.com>,
"Maciej S . Szmigiero" <maciej.szmigiero@...cle.com>,
Leo Hou <leohou1402@...il.com>, Ben Gardon <bgardon@...gle.com>
Subject: [PATCH 3/3] kvm: x86/mmu: Get/put TDP MMU root refs in iterator
To simplify acquiring and releasing references on TDP MMU root pages,
move the get/put operations into the TDP MMU root iterator macro. Not
all functions which use the macro currently get and put a reference to
the root, but adding this behavior is harmless.
Suggested-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Ben Gardon <bgardon@...gle.com>
---
arch/x86/kvm/mmu/tdp_mmu.c | 100 +++++++++++++++----------------------
1 file changed, 41 insertions(+), 59 deletions(-)
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 5ec6fae36e33..fc69216839c6 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -44,8 +44,41 @@ void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm)
WARN_ON(!list_empty(&kvm->arch.tdp_mmu_roots));
}
-#define for_each_tdp_mmu_root(_kvm, _root) \
- list_for_each_entry(_root, &_kvm->arch.tdp_mmu_roots, link)
+static void tdp_mmu_put_root(struct kvm *kvm, struct kvm_mmu_page *root)
+{
+ if (kvm_mmu_put_root(kvm, root))
+ kvm_tdp_mmu_free_root(kvm, root);
+}
+
+static inline bool tdp_mmu_next_root_valid(struct kvm *kvm,
+ struct kvm_mmu_page *root)
+{
+ if (list_entry_is_head(root, &kvm->arch.tdp_mmu_roots, link))
+ return false;
+
+ kvm_mmu_get_root(kvm, root);
+ return true;
+
+}
+
+static inline struct kvm_mmu_page *tdp_mmu_next_root(struct kvm *kvm,
+ struct kvm_mmu_page *root)
+{
+ tdp_mmu_put_root(kvm, root);
+ return list_next_entry(root, link);
+}
+
+/*
+ * Note: this iterator gets and puts references to the roots it iterates over.
+ * This makes it safe to release the MMU lock and yield within the loop, but
+ * if exiting the loop early, the caller must drop the reference to the most
+ * recent root. (Unless keeping a live reference is desirable.)
+ */
+#define for_each_tdp_mmu_root(_kvm, _root) \
+ for (_root = list_first_entry(&_kvm->arch.tdp_mmu_roots, \
+ typeof(*_root), link); \
+ tdp_mmu_next_root_valid(_kvm, _root); \
+ _root = tdp_mmu_next_root(_kvm, _root))
bool is_tdp_mmu_root(struct kvm *kvm, hpa_t hpa)
{
@@ -83,12 +116,6 @@ void kvm_tdp_mmu_free_root(struct kvm *kvm, struct kvm_mmu_page *root)
kmem_cache_free(mmu_page_header_cache, root);
}
-static void tdp_mmu_put_root(struct kvm *kvm, struct kvm_mmu_page *root)
-{
- if (kvm_mmu_put_root(kvm, root))
- kvm_tdp_mmu_free_root(kvm, root);
-}
-
static union kvm_mmu_page_role page_role_for_level(struct kvm_vcpu *vcpu,
int level)
{
@@ -134,7 +161,11 @@ static struct kvm_mmu_page *get_tdp_mmu_vcpu_root(struct kvm_vcpu *vcpu)
/* Check for an existing root before allocating a new one. */
for_each_tdp_mmu_root(kvm, root) {
if (root->role.word == role.word) {
- kvm_mmu_get_root(kvm, root);
+ /*
+ * The iterator already acquired a reference to this
+ * root, so simply return early without dropping the
+ * reference.
+ */
spin_unlock(&kvm->mmu_lock);
return root;
}
@@ -453,18 +484,9 @@ bool kvm_tdp_mmu_zap_gfn_range(struct kvm *kvm, gfn_t start, gfn_t end)
struct kvm_mmu_page *root;
bool flush = false;
- for_each_tdp_mmu_root(kvm, root) {
- /*
- * Take a reference on the root so that it cannot be freed if
- * this thread releases the MMU lock and yields in this loop.
- */
- kvm_mmu_get_root(kvm, root);
-
+ for_each_tdp_mmu_root(kvm, root)
flush |= zap_gfn_range(kvm, root, start, end, true);
- tdp_mmu_put_root(kvm, root);
- }
-
return flush;
}
@@ -626,12 +648,6 @@ static int kvm_tdp_mmu_handle_hva_range(struct kvm *kvm, unsigned long start,
int as_id;
for_each_tdp_mmu_root(kvm, root) {
- /*
- * Take a reference on the root so that it cannot be freed if
- * this thread releases the MMU lock and yields in this loop.
- */
- kvm_mmu_get_root(kvm, root);
-
as_id = kvm_mmu_page_as_id(root);
slots = __kvm_memslots(kvm, as_id);
kvm_for_each_memslot(memslot, slots) {
@@ -653,8 +669,6 @@ static int kvm_tdp_mmu_handle_hva_range(struct kvm *kvm, unsigned long start,
ret |= handler(kvm, memslot, root, gfn_start,
gfn_end, data);
}
-
- tdp_mmu_put_root(kvm, root);
}
return ret;
@@ -849,16 +863,8 @@ bool kvm_tdp_mmu_wrprot_slot(struct kvm *kvm, struct kvm_memory_slot *slot,
if (root_as_id != slot->as_id)
continue;
- /*
- * Take a reference on the root so that it cannot be freed if
- * this thread releases the MMU lock and yields in this loop.
- */
- kvm_mmu_get_root(kvm, root);
-
spte_set |= wrprot_gfn_range(kvm, root, slot->base_gfn,
slot->base_gfn + slot->npages, min_level);
-
- tdp_mmu_put_root(kvm, root);
}
return spte_set;
@@ -917,16 +923,8 @@ bool kvm_tdp_mmu_clear_dirty_slot(struct kvm *kvm, struct kvm_memory_slot *slot)
if (root_as_id != slot->as_id)
continue;
- /*
- * Take a reference on the root so that it cannot be freed if
- * this thread releases the MMU lock and yields in this loop.
- */
- kvm_mmu_get_root(kvm, root);
-
spte_set |= clear_dirty_gfn_range(kvm, root, slot->base_gfn,
slot->base_gfn + slot->npages);
-
- tdp_mmu_put_root(kvm, root);
}
return spte_set;
@@ -1040,16 +1038,8 @@ bool kvm_tdp_mmu_slot_set_dirty(struct kvm *kvm, struct kvm_memory_slot *slot)
if (root_as_id != slot->as_id)
continue;
- /*
- * Take a reference on the root so that it cannot be freed if
- * this thread releases the MMU lock and yields in this loop.
- */
- kvm_mmu_get_root(kvm, root);
-
spte_set |= set_dirty_gfn_range(kvm, root, slot->base_gfn,
slot->base_gfn + slot->npages);
-
- tdp_mmu_put_root(kvm, root);
}
return spte_set;
}
@@ -1100,16 +1090,8 @@ void kvm_tdp_mmu_zap_collapsible_sptes(struct kvm *kvm,
if (root_as_id != slot->as_id)
continue;
- /*
- * Take a reference on the root so that it cannot be freed if
- * this thread releases the MMU lock and yields in this loop.
- */
- kvm_mmu_get_root(kvm, root);
-
zap_collapsible_spte_range(kvm, root, slot->base_gfn,
slot->base_gfn + slot->npages);
-
- tdp_mmu_put_root(kvm, root);
}
}
--
2.29.2.729.g45daf8777d-goog
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