[Qemu-devel] [PATCH v4 5/7] pc: Refuse max_cpus if it results in too large APIC ID

[Eduardo Habkost <ehabkost@redhat.com>]

This changes the PC initialization code to reject max_cpus if it results
in an APIC ID that's too large, instead of aborting or erroring out when
it is already too late.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
---
Changes v3 -> v4:
 * Commit message update: removed outdated comments about
   MAX_CPUMASK_BITS

Changes v2 -> v3:
 * No need to check against MAX_CPUMASK_BITS, as MAX_CPUMASK_BITS
   is used only for CPU-index-based bitmaps on NUMA code, not for APIC
   IDs.
---
 hw/i386/pc.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 74cb4f9..14f0d91 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -992,6 +992,7 @@ void pc_cpus_init(const char *cpu_model, DeviceState *icc_bridge)
     int i;
     X86CPU *cpu = NULL;
     Error *error = NULL;
+    unsigned long apic_id_limit;
 
     /* init CPUs */
     if (cpu_model == NULL) {
@@ -1003,6 +1004,13 @@ void pc_cpus_init(const char *cpu_model, DeviceState *icc_bridge)
     }
     current_cpu_model = cpu_model;
 
+    apic_id_limit = pc_apic_id_limit(max_cpus);
+    if (apic_id_limit > ACPI_CPU_HOTPLUG_ID_LIMIT) {
+        error_report("max_cpus is too large. APIC ID of last CPU is %lu",
+                     apic_id_limit - 1);
+        exit(1);
+    }
+
     for (i = 0; i < smp_cpus; i++) {
         cpu = pc_new_cpu(cpu_model, x86_cpu_apic_id_from_index(i),
                          icc_bridge, &error);
-- 
1.8.5.3