[Qemu-devel] [PATCH v2 4/4] 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.

Currently there are two limits we need to check: the CPU hotplug APIC ID
limit (due to the AcpiCpuHotplug.sts array length), and the
MAX_CPUMASK_BITS limit (that's used for CPU bitmaps on NUMA code and
hw/i386/acpi-build.c).

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
---
 hw/i386/pc.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 74cb4f9..50376a3 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 +1004,14 @@ 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
+        || apic_id_limit > MAX_CPUMASK_BITS) {
+        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