[PATCH v3 01/28] KVM: x86/mmu: Use common iterator for walking invalid TDP MMU roots

Sean Christopherson
2022-02-26T00:16:11Z

Now that tdp_mmu_next_root() can process both valid and invalid roots,
extend it to be able to process _only_ invalid roots, add yet another
iterator macro for walking invalid roots, and use the new macro in
kvm_tdp_mmu_zap_invalidated_roots().

No functional change intended.

Reviewed-by: David Matlack <dmatlack@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/mmu/tdp_mmu.c | 74 ++++++++++++++------------------------
1 file changed, 26 insertions(+), 48 deletions(-)

diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index debf08212f12..25148e8b711d 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -98,6 +98,12 @@ void kvm_tdp_mmu_put_root(struct kvm *kvm, struct kvm_mmu_page *root,
call_rcu(&root->rcu_head, tdp_mmu_free_sp_rcu_callback);
}

+enum tdp_mmu_roots_iter_type {
+ ALL_ROOTS = -1,
+ VALID_ROOTS = 0,
+ INVALID_ROOTS = 1,
+};
+
/*
* Returns the next root after @prev_root (or the first root if @prev_root is
* NULL). A reference to the returned root is acquired, and the reference to
@@ -110,10 +116,16 @@ void kvm_tdp_mmu_put_root(struct kvm *kvm, struct kvm_mmu_page *root,
*/
static struct kvm_mmu_page *tdp_mmu_next_root(struct kvm *kvm,
struct kvm_mmu_page *prev_root,
- bool shared, bool only_valid)
+ bool shared,
+ enum tdp_mmu_roots_iter_type type)
{
struct kvm_mmu_page *next_root;

+ kvm_lockdep_assert_mmu_lock_held(kvm, shared);
+
+ /* Ensure correctness for the below comparison against role.invalid. */
+ BUILD_BUG_ON(!!VALID_ROOTS || !INVALID_ROOTS);
+
rcu_read_lock();

if (prev_root)
@@ -125,7 +137,7 @@ static struct kvm_mmu_page *tdp_mmu_next_root(struct kvm *kvm,
typeof(*next_root), link);

while (next_root) {
- if ((!only_valid || !next_root->role.invalid) &&
+ if ((type == ALL_ROOTS || (type == !!next_root->role.invalid)) &&
kvm_tdp_mmu_get_root(next_root))
break;

@@ -151,18 +163,21 @@ static struct kvm_mmu_page *tdp_mmu_next_root(struct kvm *kvm,
* mode. In the unlikely event that this thread must free a root, the lock
* will be temporarily dropped and reacquired in write mode.
*/
-#define __for_each_tdp_mmu_root_yield_safe(_kvm, _root, _as_id, _shared, _only_valid)\
- for (_root = tdp_mmu_next_root(_kvm, NULL, _shared, _only_valid); \
+#define __for_each_tdp_mmu_root_yield_safe(_kvm, _root, _as_id, _shared, _type) \
+ for (_root = tdp_mmu_next_root(_kvm, NULL, _shared, _type); \
_root; \
- _root = tdp_mmu_next_root(_kvm, _root, _shared, _only_valid)) \
- if (kvm_mmu_page_as_id(_root) != _as_id) { \
+ _root = tdp_mmu_next_root(_kvm, _root, _shared, _type)) \
+ if (_as_id > 0 && kvm_mmu_page_as_id(_root) != _as_id) { \
} else

+#define for_each_invalid_tdp_mmu_root_yield_safe(_kvm, _root) \
+ __for_each_tdp_mmu_root_yield_safe(_kvm, _root, -1, true, INVALID_ROOTS)
+
#define for_each_valid_tdp_mmu_root_yield_safe(_kvm, _root, _as_id, _shared) \
- __for_each_tdp_mmu_root_yield_safe(_kvm, _root, _as_id, _shared, true)
+ __for_each_tdp_mmu_root_yield_safe(_kvm, _root, _as_id, _shared, VALID_ROOTS)

#define for_each_tdp_mmu_root_yield_safe(_kvm, _root, _as_id, _shared) \
- __for_each_tdp_mmu_root_yield_safe(_kvm, _root, _as_id, _shared, false)
+ __for_each_tdp_mmu_root_yield_safe(_kvm, _root, _as_id, _shared, ALL_ROOTS)

#define for_each_tdp_mmu_root(_kvm, _root, _as_id) \
list_for_each_entry_rcu(_root, &_kvm->arch.tdp_mmu_roots, link, \
@@ -810,28 +825,6 @@ void kvm_tdp_mmu_zap_all(struct kvm *kvm)
kvm_flush_remote_tlbs(kvm);
}

-static struct kvm_mmu_page *next_invalidated_root(struct kvm *kvm,
- struct kvm_mmu_page *prev_root)
-{
- struct kvm_mmu_page *next_root;
-
- if (prev_root)
- next_root = list_next_or_null_rcu(&kvm->arch.tdp_mmu_roots,
- &prev_root->link,
- typeof(*prev_root), link);
- else
- next_root = list_first_or_null_rcu(&kvm->arch.tdp_mmu_roots,
- typeof(*next_root), link);
-
- while (next_root && !(next_root->role.invalid &&
- refcount_read(&next_root->tdp_mmu_root_count)))
- next_root = list_next_or_null_rcu(&kvm->arch.tdp_mmu_roots,
- &next_root->link,
- typeof(*next_root), link);
-
- return next_root;
-}
-
/*
* Since kvm_tdp_mmu_zap_all_fast has acquired a reference to each
* invalidated root, they will not be freed until this function drops the
@@ -842,36 +835,21 @@ static struct kvm_mmu_page *next_invalidated_root(struct kvm *kvm,
*/
void kvm_tdp_mmu_zap_invalidated_roots(struct kvm *kvm)
{
- struct kvm_mmu_page *next_root;
struct kvm_mmu_page *root;
bool flush = false;

lockdep_assert_held_read(&kvm->mmu_lock);

- rcu_read_lock();
-
- root = next_invalidated_root(kvm, NULL);
-
- while (root) {
- next_root = next_invalidated_root(kvm, root);
-
- rcu_read_unlock();
-
+ for_each_invalid_tdp_mmu_root_yield_safe(kvm, root) {
flush = zap_gfn_range(kvm, root, 0, -1ull, true, flush, true);

/*
- * Put the reference acquired in
- * kvm_tdp_mmu_invalidate_roots
+ * Put the reference acquired in kvm_tdp_mmu_invalidate_roots().
+ * Note, the iterator holds its own reference.
*/
kvm_tdp_mmu_put_root(kvm, root, true);
-
- root = next_root;
-
- rcu_read_lock();
}

- rcu_read_unlock();
-
if (flush)
kvm_flush_remote_tlbs(kvm);
}
--
2.35.1.574.g5d30c73bfb-goog