KVM/MMU: Flush tlb directly in the kvm_zap_gfn_range()

Originally, flush tlb is done by slot_handle_level_range(). This patch
moves the flush directly to kvm_zap_gfn_range() when range flush is
available, so that only the requested range can be flushed.

Signed-off-by: Lan Tianyu <[e-mail]>
Signed-off-by: Paolo Bonzini <[e-mail]>

arch/x86/kvm/mmu.c

···
 {
 	struct kvm_memslots *slots;
 	struct kvm_memory_slot *memslot;
+	bool flush_tlb = true;
+	bool flush = false;
 	int i;
+
+	if (kvm_available_flush_tlb_with_range())
+		flush_tlb = false;
 
 	spin_lock(&kvm->mmu_lock);
 	for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
···
 			if (start >= end)
 				continue;
 
-			slot_handle_level_range(kvm, memslot, kvm_zap_rmapp,
-						PT_PAGE_TABLE_LEVEL, PT_MAX_HUGEPAGE_LEVEL,
-						start, end - 1, true);
+			flush |= slot_handle_level_range(kvm, memslot,
+					kvm_zap_rmapp, PT_PAGE_TABLE_LEVEL,
+					PT_MAX_HUGEPAGE_LEVEL, start,
+					end - 1, flush_tlb);
 		}
 	}
+
+	if (flush)
+		kvm_flush_remote_tlbs_with_address(kvm, gfn_start,
+				gfn_end - gfn_start + 1);
 
 	spin_unlock(&kvm->mmu_lock);
 }