[PULL 12/19] hw/arm/virt: Only describe cpu topology since virt-6.2

[Richard Henderson]

From: Yanan Wang <wangyanan55@huawei.com>

On existing older machine types, without cpu topology described
in ACPI or DT, the guest will populate one by default. With the
topology described, it will read the information and set up its
topology as instructed, but that may not be the same as what was
getting used by default. It's possible that an user application
has a dependency on the default topology and if the default one
gets changed it will probably behave differently.

Based on above consideration we'd better only describe topology
information to the guest on 6.2 and later machine types.

Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Message-Id: <20211020142125.7516-2-wangyanan55@huawei.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 include/hw/arm/virt.h | 4 +++-
 hw/arm/virt.c         | 1 +
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h
index b461b8d261..dc6b66ffc8 100644
--- a/include/hw/arm/virt.h
+++ b/include/hw/arm/virt.h
@@ -125,11 +125,13 @@ struct VirtMachineClass {
     bool claim_edge_triggered_timers;
     bool smbios_old_sys_ver;
     bool no_highmem_ecam;
-    bool no_ged;   /* Machines < 4.2 has no support for ACPI GED device */
+    bool no_ged;   /* Machines < 4.2 have no support for ACPI GED device */
     bool kvm_no_adjvtime;
     bool no_kvm_steal_time;
     bool acpi_expose_flash;
     bool no_secure_gpio;
+    /* Machines < 6.2 have no support for describing cpu topology to guest */
+    bool no_cpu_topology;
 };
 
 struct VirtMachineState {
diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 4160d49688..15e8d8cf4a 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -2816,6 +2816,7 @@ static void virt_machine_6_1_options(MachineClass *mc)
     virt_machine_6_2_options(mc);
     compat_props_add(mc->compat_props, hw_compat_6_1, hw_compat_6_1_len);
     mc->smp_props.prefer_sockets = true;
+    vmc->no_cpu_topology = true;
 
     /* qemu ITS was introduced with 6.2 */
     vmc->no_tcg_its = true;
-- 
2.25.1