[Qemu-devel] [RFC 12/12] pc: Generate APIC IDs according to CPU topology

[Eduardo Habkost <ehabkost@redhat.com>]

This keeps compatibility on machine-types pc-1.2 and older, and prints a
warning in case the requested configuration won't get the correct
topology.

I couldn't think of a better way to warn about broken topology when in
compat mode other than using error_report(). The warning message will be
probably be buried in a log file somewhere, but it's better than
nothing.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
---
Changes v1 -> v2:
 - Move code to cpu.c
 - keep using cpu_index on *-user
 - Use SMP.contiguous_apic_ids global property
 - Prints warning in case the compatibility mode will expose incorrect
   topology

Changes v2 -> v3:
 - Now all code is inside hw/pc.c
 - Use a real "PC" class and a "contiguous_apic_ids" property

Changes v3 -> v4:
 - Instead of using a global property, use a separate machine init
   function and a PCInitArgs field, to implement compatibility mode
 - Use error_report() instead of fprintf(stderr) for the warning
 - Use a field on PCInitArgs instead of a static variable to check
   if warning was already printed

Changes v4 -> v5:
 - Don't use PCInitArgs: simply add a enable_compat_apic_id_mode()
   function and a static compat_apic_id_mode variable, to enable the
   compatibility mode
 - Move APIC ID calculation code to cpu.c
---
 hw/pc_piix.c      | 13 +++++++++++--
 target-i386/cpu.c | 28 ++++++++++++++++++++++++----
 target-i386/cpu.h |  1 +
 3 files changed, 36 insertions(+), 6 deletions(-)

diff --git a/hw/pc_piix.c b/hw/pc_piix.c
index 13d7cc8..be4fea1 100644
--- a/hw/pc_piix.c
+++ b/hw/pc_piix.c
@@ -233,11 +233,18 @@ static void pc_init_pci(QEMUMachineInitArgs *args)
              initrd_filename, cpu_model, 1, 1);
 }
 
+
+static void pc_init_pci_1_3(QEMUMachineInitArgs *args)
+{
+    enable_compat_apic_id_mode();
+    pc_init_pci(args);
+}
+
 /* PC machine init function for pc-0.14 to pc-1.2 */
 static void pc_init_pci_1_2(QEMUMachineInitArgs *args)
 {
     disable_kvm_pv_eoi();
-    pc_init_pci(args);
+    pc_init_pci_1_3(args);
 }
 
 /* PC init function for pc-0.10 to pc-0.13, and reused by xenfv */
@@ -250,6 +257,7 @@ static void pc_init_pci_no_kvmclock(QEMUMachineInitArgs *args)
     const char *initrd_filename = args->initrd_filename;
     const char *boot_device = args->boot_device;
     disable_kvm_pv_eoi();
+    enable_compat_apic_id_mode();
     pc_init1(get_system_memory(),
              get_system_io(),
              ram_size, boot_device,
@@ -268,6 +276,7 @@ static void pc_init_isa(QEMUMachineInitArgs *args)
     if (cpu_model == NULL)
         cpu_model = "486";
     disable_kvm_pv_eoi();
+    enable_compat_apic_id_mode();
     pc_init1(get_system_memory(),
              get_system_io(),
              ram_size, boot_device,
@@ -305,7 +314,7 @@ static QEMUMachine pc_machine_v1_4 = {
 static QEMUMachine pc_machine_v1_3 = {
     .name = "pc-1.3",
     .desc = "Standard PC",
-    .init = pc_init_pci,
+    .init = pc_init_pci_1_3,
     .max_cpus = 255,
     .compat_props = (GlobalProperty[]) {
         PC_COMPAT_1_3,
diff --git a/target-i386/cpu.c b/target-i386/cpu.c
index 33787dc..f34192c 100644
--- a/target-i386/cpu.c
+++ b/target-i386/cpu.c
@@ -23,6 +23,8 @@
 
 #include "cpu.h"
 #include "sysemu/kvm.h"
+#include "sysemu/cpus.h"
+#include "topology.h"
 
 #include "qemu/option.h"
 #include "qemu/config-file.h"
@@ -2192,6 +2194,14 @@ void x86_cpu_realize(Object *obj, Error **errp)
     cpu_reset(CPU(cpu));
 }
 
+/* Enables contiguous-apic-ID mode, for compatibility */
+static bool compat_apic_id_mode;
+
+void enable_compat_apic_id_mode(void)
+{
+    compat_apic_id_mode = true;
+}
+
 /* Calculates initial APIC ID for a specific CPU index
  *
  * Currently we need to be able to calculate the APIC ID from the CPU index
@@ -2201,10 +2211,20 @@ void x86_cpu_realize(Object *obj, Error **errp)
  */
 uint32_t apic_id_for_cpu(unsigned int cpu_index)
 {
-    /* right now APIC ID == CPU index. this will eventually change to use
-     * the CPU topology configuration properly
-     */
-    return cpu_index;
+    uint32_t correct_id;
+    static bool warned;
+
+    correct_id = topo_apicid_for_cpu(smp_cores, smp_threads, cpu_index);
+    if (compat_apic_id_mode) {
+        if (cpu_index != correct_id && !warned) {
+            error_report("APIC IDs set in compatibility mode, "
+                         "CPU topology won't match the configuration");
+            warned = true;
+        }
+        return cpu_index;
+    } else {
+        return correct_id;
+    }
 }
 
 static void x86_cpu_initfn(Object *obj)
diff --git a/target-i386/cpu.h b/target-i386/cpu.h
index dbd9899..d9a9e8f 100644
--- a/target-i386/cpu.h
+++ b/target-i386/cpu.h
@@ -1239,5 +1239,6 @@ void disable_kvm_pv_eoi(void);
 const char *get_register_name_32(unsigned int reg);
 
 uint32_t apic_id_for_cpu(unsigned int cpu_index);
+void enable_compat_apic_id_mode(void);
 
 #endif /* CPU_I386_H */
-- 
1.7.11.7