diff --git a/xen/arch/x86/cpuid.c b/xen/arch/x86/cpuid.c
index 2a777436ee27..dcbdeabadce9 100644
--- a/xen/arch/x86/cpuid.c
+++ b/xen/arch/x86/cpuid.c
@@ -138,10 +138,9 @@ void guest_cpuid(const struct vcpu *v, uint32_t leaf,
         const struct cpu_user_regs *regs;
 
     case 0x1:
-        /* TODO: Rework topology logic. */
         res->b &= 0x00ffffffu;
         if ( is_hvm_domain(d) )
-            res->b |= (v->vcpu_id * 2) << 24;
+            res->b |= vlapic_x2apic_id(vcpu_vlapic(v)) << 24;
 
         /* TODO: Rework vPMU control in terms of toolstack choices. */
         if ( vpmu_available(v) &&
@@ -311,18 +310,15 @@ void guest_cpuid(const struct vcpu *v, uint32_t leaf,
 
     case 0xb:
         /*
-         * In principle, this leaf is Intel-only.  In practice, it is tightly
-         * coupled with x2apic, and we offer an x2apic-capable APIC emulation
-         * to guests on AMD hardware as well.
-         *
-         * TODO: Rework topology logic.
+         * Don't expose topology information to PV guests. Exposed on HVM
+         * along with x2APIC because they are tightly coupled.
          */
-        if ( p->basic.x2apic )
+        if ( is_hvm_domain(d) && p->basic.x2apic )
         {
             *(uint8_t *)&res->c = subleaf;
 
             /* Fix the x2APIC identifier. */
-            res->d = v->vcpu_id * 2;
+            res->d = vlapic_x2apic_id(vcpu_vlapic(v));
         }
         break;
 
diff --git a/xen/arch/x86/hvm/vlapic.c b/xen/arch/x86/hvm/vlapic.c
index 101902cff889..02570f9dd63a 100644
--- a/xen/arch/x86/hvm/vlapic.c
+++ b/xen/arch/x86/hvm/vlapic.c
@@ -1090,7 +1090,7 @@ static uint32_t x2apic_ldr_from_id(uint32_t id)
 static void set_x2apic_id(struct vlapic *vlapic)
 {
     const struct vcpu *v = vlapic_vcpu(vlapic);
-    uint32_t apic_id = v->vcpu_id * 2;
+    uint32_t apic_id = vlapic->hw.x2apic_id;
     uint32_t apic_ldr = x2apic_ldr_from_id(apic_id);
 
     /*
@@ -1470,7 +1470,7 @@ void vlapic_reset(struct vlapic *vlapic)
     if ( v->vcpu_id == 0 )
         vlapic->hw.apic_base_msr |= APIC_BASE_BSP;
 
-    vlapic_set_reg(vlapic, APIC_ID, (v->vcpu_id * 2) << 24);
+    vlapic_set_reg(vlapic, APIC_ID, SET_xAPIC_ID(vlapic->hw.x2apic_id));
     vlapic_do_init(vlapic);
 }
 
@@ -1538,6 +1538,16 @@ static void lapic_load_fixup(struct vlapic *vlapic)
     const struct vcpu *v = vlapic_vcpu(vlapic);
     uint32_t good_ldr = x2apic_ldr_from_id(vlapic->loaded.id);
 
+    /*
+     * Loading record without hw.x2apic_id in the save stream, calculate using
+     * the traditional "vcpu_id * 2" relation. There's an implicit assumption
+     * that vCPU0 always has x2APIC0, which is true for the old relation, and
+     * still holds under the new x2APIC generation algorithm. While that case
+     * goes through the conditional it's benign because it still maps to zero.
+     */
+    if ( !vlapic->hw.x2apic_id )
+        vlapic->hw.x2apic_id = v->vcpu_id * 2;
+
     /* Skip fixups on xAPIC mode, or if the x2APIC LDR is already correct */
     if ( !vlapic_x2apic_mode(vlapic) ||
          (vlapic->loaded.ldr == good_ldr) )
@@ -1606,6 +1616,13 @@ static int cf_check lapic_check_hidden(const struct domain *d,
          APIC_BASE_EXTD )
         return -EINVAL;
 
+    /*
+     * Fail migrations from newer versions of Xen where
+     * rsvd_zero is interpreted as something else.
+     */
+    if ( s.rsvd_zero )
+        return -EINVAL;
+
     return 0;
 }
 
@@ -1687,6 +1704,7 @@ int vlapic_init(struct vcpu *v)
     }
 
     vlapic->pt.source = PTSRC_lapic;
+    vlapic->hw.x2apic_id = 2 * v->vcpu_id;
 
     vlapic->regs_page = alloc_domheap_page(v->domain, MEMF_no_owner);
     if ( !vlapic->regs_page )
diff --git a/xen/arch/x86/include/asm/hvm/vlapic.h b/xen/arch/x86/include/asm/hvm/vlapic.h
index 2c4ff94ae7a8..85c4a236b9f6 100644
--- a/xen/arch/x86/include/asm/hvm/vlapic.h
+++ b/xen/arch/x86/include/asm/hvm/vlapic.h
@@ -44,6 +44,7 @@
 #define vlapic_xapic_mode(vlapic)                               \
     (!vlapic_hw_disabled(vlapic) && \
      !((vlapic)->hw.apic_base_msr & APIC_BASE_EXTD))
+#define vlapic_x2apic_id(vlapic) ((vlapic)->hw.x2apic_id)
 
 /*
  * Generic APIC bitmap vector update & search routines.
diff --git a/xen/include/public/arch-x86/hvm/save.h b/xen/include/public/arch-x86/hvm/save.h
index 7ecacadde165..1c2ec669ffc9 100644
--- a/xen/include/public/arch-x86/hvm/save.h
+++ b/xen/include/public/arch-x86/hvm/save.h
@@ -394,6 +394,8 @@ struct hvm_hw_lapic {
     uint32_t             disabled; /* VLAPIC_xx_DISABLED */
     uint32_t             timer_divisor;
     uint64_t             tdt_msr;
+    uint32_t             x2apic_id;
+    uint32_t             rsvd_zero;
 };
 
 DECLARE_HVM_SAVE_TYPE(LAPIC, 5, struct hvm_hw_lapic);
