[PATCH 16/23] KVM: x86/mmu: Zap collapsible SPTEs at all levels in the shadow MMU

[David Matlack <dmatlack@google.com>]

Currently KVM only zaps collapsible 4KiB SPTEs in the shadow MMU (i.e.
in the rmap). This leads to correct behavior because KVM never creates
intermediate huge pages during dirty logging. For example, a 1GiB page
is never partially split to a 2MiB page.

However this behavior will stop being correct once the shadow MMU
participates in eager page splitting, which can in fact leave behind
partially split huge pages. In preparation for that change, change the
shadow MMU to iterate over all levels when zapping collapsible SPTEs.

No functional change intended.

Signed-off-by: David Matlack <dmatlack@google.com>
---
 arch/x86/kvm/mmu/mmu.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index e2306a39526a..99ad7cc8683f 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -6038,18 +6038,25 @@ static bool kvm_mmu_zap_collapsible_spte(struct kvm *kvm,
 	return need_tlb_flush;
 }
 
+static void kvm_rmap_zap_collapsible_sptes(struct kvm *kvm,
+					   const struct kvm_memory_slot *slot)
+{
+	bool flush;
+
+	flush = slot_handle_level(kvm, slot, kvm_mmu_zap_collapsible_spte,
+				  PG_LEVEL_4K, KVM_MAX_HUGEPAGE_LEVEL, true);
+
+	if (flush)
+		kvm_arch_flush_remote_tlbs_memslot(kvm, slot);
+
+}
+
 void kvm_mmu_zap_collapsible_sptes(struct kvm *kvm,
 				   const struct kvm_memory_slot *slot)
 {
 	if (kvm_memslots_have_rmaps(kvm)) {
 		write_lock(&kvm->mmu_lock);
-		/*
-		 * Zap only 4k SPTEs since the legacy MMU only supports dirty
-		 * logging at a 4k granularity and never creates collapsible
-		 * 2m SPTEs during dirty logging.
-		 */
-		if (slot_handle_level_4k(kvm, slot, kvm_mmu_zap_collapsible_spte, true))
-			kvm_arch_flush_remote_tlbs_memslot(kvm, slot);
+		kvm_rmap_zap_collapsible_sptes(kvm, slot);
 		write_unlock(&kvm->mmu_lock);
 	}
 
-- 
2.35.0.rc2.247.g8bbb082509-goog