diff --git a/xen/arch/x86/cpu/common.c b/xen/arch/x86/cpu/common.c
index 77364fd728..08261edf17 100644
--- a/xen/arch/x86/cpu/common.c
+++ b/xen/arch/x86/cpu/common.c
@@ -415,6 +415,22 @@ void __init early_cpu_init(bool verbose)
 	initialize_cpu_data(0);
 }
 
+void reset_cpuinfo(struct cpuinfo_x86 *c, bool keep_basic)
+{
+    if ( !keep_basic )
+    {
+        c->x86_vendor = 0;
+        c->x86 = 0;
+        c->x86_model = 0;
+        c->x86_mask = 0;
+        memset(&c->x86_capability, 0, sizeof(c->x86_capability));
+        memset(&c->x86_vendor_id, 0, sizeof(c->x86_vendor_id));
+        memset(&c->x86_model_id, 0, sizeof(c->x86_model_id));
+    }
+
+    CPU_DATA_INIT((*c));
+}
+
 static void generic_identify(struct cpuinfo_x86 *c)
 {
 	u32 eax, ebx, ecx, edx, tmp;
@@ -522,16 +538,7 @@ void identify_cpu(struct cpuinfo_x86 *c)
 {
 	int i;
 
-	c->x86_cache_size = -1;
-	c->x86_model = c->x86_mask = 0;	/* So far unknown... */
-	c->x86_model_id[0] = '\0';  /* Unset */
-	c->x86_max_cores = 1;
-	c->x86_num_siblings = 1;
-	c->x86_clflush_size = 0;
-	c->cpu_core_id = XEN_INVALID_CORE_ID;
-	c->compute_unit_id = INVALID_CUID;
-	memset(&c->x86_capability, 0, sizeof c->x86_capability);
-
+	reset_cpuinfo(c, false);
 	generic_identify(c);
 
 #ifdef NOISY_CAPS
diff --git a/xen/arch/x86/include/asm/cpufeature.h b/xen/arch/x86/include/asm/cpufeature.h
index 3c2ac964e4..56d6ed1a87 100644
--- a/xen/arch/x86/include/asm/cpufeature.h
+++ b/xen/arch/x86/include/asm/cpufeature.h
@@ -41,6 +41,24 @@ struct cpuinfo_x86 {
     unsigned short x86_clflush_size;
 } __cacheline_aligned;
 
+#define CPU_DATA_INIT(what...)                     \
+        what.cpuid_level = 1,                      \
+        what.extended_cpuid_level = 0,             \
+        what.x86_cache_size = -1,                  \
+        what.x86_max_cores = 1,                    \
+        what.x86_num_siblings = 1,                 \
+        what.apicid = BAD_APICID,                  \
+        what.phys_proc_id = XEN_INVALID_SOCKET_ID, \
+        what.cpu_core_id = XEN_INVALID_CORE_ID,    \
+        what.compute_unit_id = INVALID_CUID
+
+/*
+ * @keep_basic set to true retains data firmly assumed to be symmetric
+ * across all CPUs.  With it set to false only CPU_DATA_INIT() will be
+ * invoked on the passed structure.
+ */
+void reset_cpuinfo(struct cpuinfo_x86 *c, bool keep_basic);
+
 extern struct cpuinfo_x86 boot_cpu_data;
 
 static inline bool cpu_has(const struct cpuinfo_x86 *info, unsigned int feat)
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 24e4f5ac7f..c6890669b9 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -178,7 +178,7 @@ void *stack_start = cpu0_stack + STACK_SIZE - sizeof(struct cpu_info);
 /* Used by the boot asm and EFI to stash the multiboot_info paddr. */
 unsigned int __initdata multiboot_ptr;
 
-struct cpuinfo_x86 __read_mostly boot_cpu_data = { 0, 0, 0, 0, -1 };
+struct cpuinfo_x86 __read_mostly boot_cpu_data = { CPU_DATA_INIT() };
 
 unsigned long __read_mostly mmu_cr4_features = XEN_MINIMAL_CR4;
 
diff --git a/xen/arch/x86/smpboot.c b/xen/arch/x86/smpboot.c
index a90caf45a5..25bdd98fcf 100644
--- a/xen/arch/x86/smpboot.c
+++ b/xen/arch/x86/smpboot.c
@@ -69,7 +69,8 @@ unsigned int __read_mostly nr_sockets;
 cpumask_t **__read_mostly socket_cpumask;
 static cpumask_t *secondary_socket_cpumask;
 
-struct cpuinfo_x86 cpu_data[NR_CPUS];
+struct cpuinfo_x86 __read_mostly cpu_data[NR_CPUS] =
+    { [0 ... NR_CPUS - 1] = { CPU_DATA_INIT() } };
 
 u32 x86_cpu_to_apicid[NR_CPUS] __read_mostly =
 	{ [0 ... NR_CPUS-1] = BAD_APICID };
@@ -89,7 +90,12 @@ void *stack_base[NR_CPUS];
 
 void initialize_cpu_data(unsigned int cpu)
 {
-    cpu_data[cpu] = boot_cpu_data;
+    struct cpuinfo_x86 c = boot_cpu_data;
+
+    /* Must not partially clear the BSP's collected data. */
+    if ( cpu || system_state > SYS_STATE_smp_boot )
+        reset_cpuinfo(&c, true);
+    cpu_data[cpu] = c;
 }
 
 static bool smp_store_cpu_info(unsigned int id)
@@ -968,9 +974,7 @@ static void cpu_smpboot_free(unsigned int cpu, bool remove)
 
     if ( remove )
     {
-        c[cpu].phys_proc_id = XEN_INVALID_SOCKET_ID;
-        c[cpu].cpu_core_id = XEN_INVALID_CORE_ID;
-        c[cpu].compute_unit_id = INVALID_CUID;
+        reset_cpuinfo(&c[cpu], false);
 
         FREE_CPUMASK_VAR(per_cpu(cpu_sibling_mask, cpu));
         FREE_CPUMASK_VAR(per_cpu(cpu_core_mask, cpu));