+static void mmu_guess_page_from_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
+ const u8 *new, int bytes)
+{
+ gfn_t gfn;
+ int r;
+ u64 gpte = 0;
+
+ if (bytes != 4 && bytes != 8)
+ return;
+
+ /*
+ * Assume that the pte write on a page table of the same type
+ * as the current vcpu paging mode. This is nearly always true
+ * (might be false while changing modes). Note it is verified later
+ * by update_pte().
+ */
+ if (is_pae(vcpu)) {
+ /* Handle a 32-bit guest writing two halves of a 64-bit gpte */
+ if ((bytes == 4) && (gpa % 4 == 0)) {
+ r = kvm_read_guest(vcpu->kvm, gpa & ~(u64)7, &gpte, 8);
+ if (r)
+ return;
+ memcpy((void *)&gpte + (gpa % 8), new, 4);
+ } else if ((bytes == 8) && (gpa % 8 == 0)) {
+ memcpy((void *)&gpte, new, 8);
+ }
+ } else {
+ if ((bytes == 4) && (gpa % 4 == 0))
+ memcpy((void *)&gpte, new, 4);
+ }
+ if (!is_present_pte(gpte))
+ return;
+ gfn = (gpte & PT64_BASE_ADDR_MASK) >> PAGE_SHIFT;
+ vcpu->arch.update_pte.gfn = gfn;
+ vcpu->arch.update_pte.page = gfn_to_page(vcpu->kvm, gfn);
+}
+