[qemu-xen staging-4.13] x86: do not advertise die-id in query-hotpluggbale-cpus if '-smp dies' is not set

[patchbot@xxxxxxx]

commit 725dfa851f8e1de8653f41a4bd38c7f98757eb40
Author:     Igor Mammedov <imammedo@xxxxxxxxxx>
AuthorDate: Mon Sep 2 08:02:22 2019 -0400
Commit:     Michael Roth <mdroth@xxxxxxxxxxxxxxxxxx>
CommitDate: Sun Oct 27 23:50:01 2019 -0500

    x86: do not advertise die-id in query-hotpluggbale-cpus if '-smp dies' is 
not set
    
    Commit 176d2cda0 (i386/cpu: Consolidate die-id validity in smp context) 
added
    new 'die-id' topology property to CPUs and exposed it via QMP command
    query-hotpluggable-cpus, which broke -device/device_add cpu-foo for existing
    users that do not support die-id/dies yet. That's would be fine if it 
happened
    to new machine type only but it also happened to old machine types,
    which breaks migration from old QEMU to the new one, for example following 
CLI:
    
      OLD-QEMU -M pc-i440fx-4.0 -smp 1,max_cpus=2 \
               -device qemu64-x86_64-cpu,socket-id=1,core-id=0,thread-id
    is not able to start with new QEMU, complaining about invalid die-id.
    
    After discovering regression, the patch
       "pc: Don't make die-id mandatory unless necessary"
    makes die-id optional so old CLI would work.
    
    However it's not enough as new QEMU still exposes die-id via 
query-hotpluggbale-cpus
    QMP command, so the users that started old machine type on new QEMU, using 
all
    properties (including die-id) received from QMP command (as required), 
won't be
    able to start old QEMU using the same properties since it doesn't support 
die-id.
    
    Fix it by hiding die-id in query-hotpluggbale-cpus for all machine types in 
case
    '-smp dies' is not provided on CLI or -smp dies = 1', in which case 
smp_dies == 1
    and APIC ID is calculated in default way (as it was before DIE support) so 
we won't
    need compat code as in both cases the topology provided to guest via CPUID 
is the same.
    
    Signed-off-by: Igor Mammedov <imammedo@xxxxxxxxxx>
    Message-Id: <20190902120222.6179-1-imammedo@xxxxxxxxxx>
    Reviewed-by: Eduardo Habkost <ehabkost@xxxxxxxxxx>
    Signed-off-by: Eduardo Habkost <ehabkost@xxxxxxxxxx>
    (cherry picked from commit c6c1bb89fb46f3b88f832e654cf5a6f7941aac51)
    Signed-off-by: Michael Roth <mdroth@xxxxxxxxxxxxxxxxxx>
---
 hw/i386/pc.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 947f81070f..d011733ff7 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -2887,8 +2887,10 @@ static const CPUArchIdList 
*pc_possible_cpu_arch_ids(MachineState *ms)
                                  ms->smp.threads, &topo);
         ms->possible_cpus->cpus[i].props.has_socket_id = true;
         ms->possible_cpus->cpus[i].props.socket_id = topo.pkg_id;
-        ms->possible_cpus->cpus[i].props.has_die_id = true;
-        ms->possible_cpus->cpus[i].props.die_id = topo.die_id;
+        if (pcms->smp_dies > 1) {
+            ms->possible_cpus->cpus[i].props.has_die_id = true;
+            ms->possible_cpus->cpus[i].props.die_id = topo.die_id;
+        }
         ms->possible_cpus->cpus[i].props.has_core_id = true;
         ms->possible_cpus->cpus[i].props.core_id = topo.core_id;
         ms->possible_cpus->cpus[i].props.has_thread_id = true;
--
generated by git-patchbot for /home/xen/git/qemu-xen.git#staging-4.13