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-rw-r--r--hw/i386/pc.c8
-rw-r--r--hw/i386/x86.c16
2 files changed, 16 insertions, 8 deletions
diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 312eb9e400..15f37d8dc6 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -744,14 +744,6 @@ void pc_machine_done(Notifier *notifier, void *data)
         /* update FW_CFG_NB_CPUS to account for -device added CPUs */
         fw_cfg_modify_i16(x86ms->fw_cfg, FW_CFG_NB_CPUS, x86ms->boot_cpus);
     }
-
-
-    if (x86ms->apic_id_limit > 255 && !xen_enabled() &&
-        !kvm_irqchip_in_kernel()) {
-        error_report("current -smp configuration requires kernel "
-                     "irqchip support.");
-        exit(EXIT_FAILURE);
-    }
 }
 
 void pc_guest_info_init(PCMachineState *pcms)
diff --git a/hw/i386/x86.c b/hw/i386/x86.c
index 79ebdface6..f79e720cc2 100644
--- a/hw/i386/x86.c
+++ b/hw/i386/x86.c
@@ -38,6 +38,7 @@
 #include "sysemu/replay.h"
 #include "sysemu/sysemu.h"
 #include "sysemu/cpu-timers.h"
+#include "sysemu/xen.h"
 #include "trace.h"
 
 #include "hw/i386/x86.h"
@@ -122,6 +123,21 @@ void x86_cpus_init(X86MachineState *x86ms, int default_cpu_version)
      */
     x86ms->apic_id_limit = x86_cpu_apic_id_from_index(x86ms,
                                                       ms->smp.max_cpus - 1) + 1;
+
+    /*
+     * Can we support APIC ID 255 or higher?
+     *
+     * Under Xen: yes.
+     * With userspace emulated lapic: no
+     * With KVM's in-kernel lapic: only if X2APIC API is enabled.
+     */
+    if (x86ms->apic_id_limit > 255 && !xen_enabled() &&
+        (!kvm_irqchip_in_kernel() || !kvm_enable_x2apic())) {
+        error_report("current -smp configuration requires kernel "
+                     "irqchip and X2APIC API support.");
+        exit(EXIT_FAILURE);
+    }
+
     possible_cpus = mc->possible_cpu_arch_ids(ms);
     for (i = 0; i < ms->smp.cpus; i++) {
         x86_cpu_new(x86ms, possible_cpus->cpus[i].arch_id, &error_fatal);