[Qemu-devel] [PATCH 12/12] target-i386: implement CPU hot-add

[Igor Mammedov <imammedo@redhat.com>]

... via do_cpu_hot_add() hook called by cpu_set QMP command,
for x86 target.

* add extra check that APIC ID is in allowed range
* return error if CPU with requested APIC ID exists before creating
  a new instance. (CPU removal is broken now, will be fixed with CPU unplug)
* call CPU add notifier as the last step of x86_cpu_realizefn() to
  update rtc_cmos and trigger CPU hot-plug ACPI GPE to notify guest.
  Doing it from x86_cpu_realizefn() will allow to do the same when
  it would be possible to add CPU using device_add.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
---
 hw/i386/pc.c      |   22 ++++++++++++++++++++++
 target-i386/cpu.c |    1 +
 2 files changed, 23 insertions(+), 0 deletions(-)

diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 7481f73..e3ba9ee 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -867,6 +867,19 @@ static void pc_new_cpu(const char *cpu_model, int64_t apic_id, Error **errp)
 {
     X86CPU *cpu;
 
+    if (apic_id >= pc_apic_id_limit(max_cpus)) {
+        error_setg(errp, "Unable to add CPU with ID: 0x%" PRIx64
+                   ", max allowed ID: 0x%x", apic_id,
+                   pc_apic_id_limit(max_cpus) - 1);
+        return;
+    }
+
+    if (x86_cpu_is_cpu_exist(qdev_get_machine(), &apic_id)) {
+        error_setg(errp, "Unable to add CPU with ID: 0x%" PRIx64
+                   ", it's already exists", apic_id);
+        return;
+    }
+
     cpu = cpu_x86_create(cpu_model, errp);
     if (!cpu) {
         return;
@@ -882,6 +895,8 @@ static void pc_new_cpu(const char *cpu_model, int64_t apic_id, Error **errp)
     }
 }
 
+static const char *saved_cpu_model;
+
 void pc_cpus_init(const char *cpu_model)
 {
     int i;
@@ -895,6 +910,8 @@ void pc_cpus_init(const char *cpu_model)
         cpu_model = "qemu32";
 #endif
     }
+    saved_cpu_model = cpu_model;
+
 
     for (i = 0; i < smp_cpus; i++) {
         pc_new_cpu(cpu_model, x86_cpu_apic_id_from_index(i), &error);
@@ -906,6 +923,11 @@ void pc_cpus_init(const char *cpu_model)
     }
 }
 
+void do_cpu_hot_add(const int64_t id, Error **errp)
+{
+    pc_new_cpu(saved_cpu_model, id, errp);
+}
+
 void pc_acpi_init(const char *default_dsdt)
 {
     char *filename = NULL, *arg = NULL;
diff --git a/target-i386/cpu.c b/target-i386/cpu.c
index ae46f81..d127141 100644
--- a/target-i386/cpu.c
+++ b/target-i386/cpu.c
@@ -2271,6 +2271,7 @@ out:
     if (dev->hotplugged) {
         cpu_synchronize_post_init(env);
         resume_vcpu(CPU(cpu));
+        qemu_system_cpu_hotplug_request(env->cpuid_apic_id);
     }
 }
 
-- 
1.7.1