The existing TDP MMU methods to handle dirty logging are vcpu-agnostic
since they can be driven by MMU notifiers and other non-vcpu-specific
events in addition to page faults. However this means that the TDP MMU
is not benefiting from the new vcpu->last_used_slot. Fix that by
introducing a tdp_mmu_map_set_spte_atomic() which is only called during
a TDP page fault and has access to the kvm_vcpu for fast slot lookups.
This improves "Populate memory time" in dirty_log_perf_test by 5%:
Command | Before | After
------------------------------- | ---------------- | -------------
./dirty_log_perf_test -v64 -x64 | 5.472321072s | 5.169832886s
Signed-off-by: David Matlack <dmatlack@xxxxxxxxxx>
---
arch/x86/kvm/mmu/tdp_mmu.c | 42 ++++++++++++++++++++++++++++++--------
1 file changed, 33 insertions(+), 9 deletions(-)
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 43f12f5d12c0..dab6cb46cdb2 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -542,15 +542,40 @@ static inline bool tdp_mmu_set_spte_atomic_no_dirty_log(struct kvm *kvm,
return true;
}
-static inline bool tdp_mmu_set_spte_atomic(struct kvm *kvm,
- struct tdp_iter *iter,
- u64 new_spte)
+/*
+ * tdp_mmu_map_set_spte_atomic - Set a leaf TDP MMU SPTE atomically to resolve a
+ * TDP page fault.
+ *
+ * @vcpu: The vcpu instance that took the TDP page fault.
+ * @iter: a tdp_iter instance currently on the SPTE that should be set
+ * @new_spte: The value the SPTE should be set to
+ *
+ * Returns: true if the SPTE was set, false if it was not. If false is returned,
+ * this function will have no side-effects.
+ */
+static inline bool tdp_mmu_map_set_spte_atomic(struct kvm_vcpu *vcpu,
+ struct tdp_iter *iter,
+ u64 new_spte)
{
+ struct kvm *kvm = vcpu->kvm;
+
if (!tdp_mmu_set_spte_atomic_no_dirty_log(kvm, iter, new_spte))
return false;
- handle_changed_spte_dirty_log(kvm, iter->as_id, iter->gfn,
- iter->old_spte, new_spte, iter->level);
+ /*
+ * Use kvm_vcpu_gfn_to_memslot() instead of going through
+ * handle_changed_spte_dirty_log() to leverage vcpu->last_used_slot.
+ */
+ if (is_writable_pte(new_spte)) {
+ struct kvm_memory_slot *slot = kvm_vcpu_gfn_to_memslot(vcpu, iter->gfn);
+
+ if (slot && kvm_slot_dirty_track_enabled(slot)) {
+ /* Enforced by kvm_mmu_hugepage_adjust. */
+ WARN_ON_ONCE(iter->level > PG_LEVEL_4K);
+ mark_page_dirty_in_slot(kvm, slot, iter->gfn);
+ }
+ }
+
return true;
}
@@ -563,7 +588,7 @@ static inline bool tdp_mmu_zap_spte_atomic(struct kvm *kvm,
* immediately installing a present entry in its place
* before the TLBs are flushed.
*/
- if (!tdp_mmu_set_spte_atomic(kvm, iter, REMOVED_SPTE))
+ if (!tdp_mmu_set_spte_atomic_no_dirty_log(kvm, iter, REMOVED_SPTE))
return false;
kvm_flush_remote_tlbs_with_address(kvm, iter->gfn,
@@ -931,7 +956,7 @@ static int tdp_mmu_map_handle_target_level(struct kvm_vcpu *vcpu, int write,
if (new_spte == iter->old_spte)
ret = RET_PF_SPURIOUS;
- else if (!tdp_mmu_set_spte_atomic(vcpu->kvm, iter, new_spte))
+ else if (!tdp_mmu_map_set_spte_atomic(vcpu, iter, new_spte))
return RET_PF_RETRY;
/*
@@ -1035,8 +1060,7 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
new_spte = make_nonleaf_spte(child_pt,
!shadow_accessed_mask);
- if (tdp_mmu_set_spte_atomic(vcpu->kvm, &iter,
- new_spte)) {
+ if (tdp_mmu_set_spte_atomic_no_dirty_log(vcpu->kvm, &iter, new_spte)) {
tdp_mmu_link_page(vcpu->kvm, sp, true,
huge_page_disallowed &&
req_level >= iter.level);
--
2.32.0.554.ge1b32706d8-goog
