-----Original Message-----
From: kvm-owner at vger.kernel.org [mailto:kvm-owner at vger.kernel.org] On
Behalf Of Christoffer Dall
Sent: Monday, October 01, 2012 6:11 PM
To: kvm at vger.kernel.org; linux-arm-kernel at lists.infradead.org;
kvmarm at lists.cs.columbia.edu
Cc: Marc Zyngier
Subject: [PATCH v2 06/14] KVM: ARM: Memory virtualization setup

+static void stage2_set_pte(struct kvm *kvm, struct kvm_mmu_memory_cache
*cache,
+			   phys_addr_t addr, const pte_t *new_pte) {
+	pgd_t *pgd;
+	pud_t *pud;
+	pmd_t *pmd;
+	pte_t *pte, old_pte;
+
+	/* Create 2nd stage page table mapping - Level 1 */
+	pgd = kvm->arch.pgd + pgd_index(addr);
+	pud = pud_offset(pgd, addr);
+	if (pud_none(*pud)) {
+		if (!cache)
+			return; /* ignore calls from kvm_set_spte_hva */
+		pmd = mmu_memory_cache_alloc(cache);
+		pud_populate(NULL, pud, pmd);
+		pmd += pmd_index(addr);
+		get_page(virt_to_page(pud));
+	} else
+		pmd = pmd_offset(pud, addr);
+
+	/* Create 2nd stage page table mapping - Level 2 */
+	if (pmd_none(*pmd)) {
+		if (!cache)
+			return; /* ignore calls from kvm_set_spte_hva */
+		pte = mmu_memory_cache_alloc(cache);
+		clean_pte_table(pte);
+		pmd_populate_kernel(NULL, pmd, pte);
+		pte += pte_index(addr);
+		get_page(virt_to_page(pmd));
+	} else
+		pte = pte_offset_kernel(pmd, addr);
+
+	/* Create 2nd stage page table mapping - Level 3 */
+	old_pte = *pte;
+	set_pte_ext(pte, *new_pte, 0);
+	if (pte_present(old_pte))
+		__kvm_tlb_flush_vmid(kvm);
+	else
+		get_page(virt_to_page(pte));
+}

I'm not sure about the 3-level page table, but isn't it necessary to
clean the page table for 2nd level?
There are two mmu_memory_cache_alloc calls. One has following clean_pte_table
and the other doesn't have. 

And why do you ignore calls from kvm_set_spte_hva? It is supposed to happen when
host moves the page, right? Then you ignore the case because it can be handled
later when fault actually happens? Is there any other reason that I miss?