[PATCH v2 12/12] KVM: MMU: fast drop all spte on the pte_list

[Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx>]

If the pte_list need to be destroyed, no need to delete its spte one
by one, we can directly reset it and free the memory its used

Signed-off-by: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx>
---
 arch/x86/kvm/mmu.c |   36 +++++++++++++++++++++++++++---------
 1 files changed, 27 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 2c0a786..0afe8da 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -968,6 +968,25 @@ static void pte_list_remove(u64 *spte, unsigned long *pte_list)
 	}
 }

+static void pte_list_destroy(unsigned long *pte_list)
+{
+	struct pte_list_desc *desc;
+	unsigned long list_value = *pte_list;
+
+	*pte_list = 0;
+
+	if (!(list_value & 1))
+		return;
+
+	desc = (struct pte_list_desc *)(list_value & ~1ul);
+	while (desc) {
+		struct pte_list_desc *next_desc = desc->more;
+
+		mmu_free_pte_list_desc(desc);
+		desc = next_desc;
+	}
+}
+
 /*
  * Used by the following functions to iterate through the sptes linked by a
  * pte_list.  All fields are private and not assumed to be used outside.
@@ -1206,17 +1225,17 @@ static bool rmap_write_protect(struct kvm *kvm, u64 gfn)
 static int kvm_unmap_rmapp(struct kvm *kvm, unsigned long *rmapp,
 			   struct kvm_memory_slot *slot, unsigned long data)
 {
-	u64 *sptep;
 	struct pte_list_iterator iter;
+	u64 *sptep;
 	int need_tlb_flush = 0;

-restart:
 	for_each_spte_in_rmap(*rmapp, iter, sptep) {
-		drop_spte(kvm, sptep);
+		mmu_spte_clear_track_bits(sptep);
 		need_tlb_flush = 1;
-		goto restart;
 	}

+	pte_list_destroy(rmapp);
+
 	return need_tlb_flush;
 }

@@ -2041,11 +2060,10 @@ static void kvm_mmu_unlink_parents(struct kvm *kvm, struct kvm_mmu_page *sp)
 	u64 *sptep;
 	struct pte_list_iterator iter;

-restart:
-	for_each_spte_in_rmap(sp->parent_ptes, iter, sptep) {
-		drop_parent_pte(sp, sptep);
-		goto restart;
-	}
+	for_each_spte_in_rmap(sp->parent_ptes, iter, sptep)
+		mmu_spte_clear_no_track(sptep);
+
+	pte_list_destroy(&sp->parent_ptes);
 }

 static int mmu_zap_unsync_children(struct kvm *kvm,
-- 
1.7.7.6

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