[PULL 31/32] hw/arm/virt: Fix CPU's default NUMA node ID

[Peter Maydell <peter.maydell@linaro.org>]

From: Gavin Shan <gshan@redhat.com>

When CPU-to-NUMA association isn't explicitly provided by users,
the default one is given by mc->get_default_cpu_node_id(). However,
the CPU topology isn't fully considered in the default association
and this causes CPU topology broken warnings on booting Linux guest.

For example, the following warning messages are observed when the
Linux guest is booted with the following command lines.

  /home/gavin/sandbox/qemu.main/build/qemu-system-aarch64 \
  -accel kvm -machine virt,gic-version=host               \
  -cpu host                                               \
  -smp 6,sockets=2,cores=3,threads=1                      \
  -m 1024M,slots=16,maxmem=64G                            \
  -object memory-backend-ram,id=mem0,size=128M            \
  -object memory-backend-ram,id=mem1,size=128M            \
  -object memory-backend-ram,id=mem2,size=128M            \
  -object memory-backend-ram,id=mem3,size=128M            \
  -object memory-backend-ram,id=mem4,size=128M            \
  -object memory-backend-ram,id=mem4,size=384M            \
  -numa node,nodeid=0,memdev=mem0                         \
  -numa node,nodeid=1,memdev=mem1                         \
  -numa node,nodeid=2,memdev=mem2                         \
  -numa node,nodeid=3,memdev=mem3                         \
  -numa node,nodeid=4,memdev=mem4                         \
  -numa node,nodeid=5,memdev=mem5
         :
  alternatives: patching kernel code
  BUG: arch topology borken
  the CLS domain not a subset of the MC domain
  <the above error log repeats>
  BUG: arch topology borken
  the DIE domain not a subset of the NODE domain

With current implementation of mc->get_default_cpu_node_id(),
CPU#0 to CPU#5 are associated with NODE#0 to NODE#5 separately.
That's incorrect because CPU#0/1/2 should be associated with same
NUMA node because they're seated in same socket.

This fixes the issue by considering the socket ID when the default
CPU-to-NUMA association is provided in virt_possible_cpu_arch_ids().
With this applied, no more CPU topology broken warnings are seen
from the Linux guest. The 6 CPUs are associated with NODE#0/1, but
there are no CPUs associated with NODE#2/3/4/5.

Signed-off-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Yanan Wang <wangyanan55@huawei.com>
Message-id: 20220503140304.855514-6-gshan@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 hw/arm/virt.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index c25023a083a..1a45f44435e 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -2554,7 +2554,9 @@ virt_cpu_index_to_props(MachineState *ms, unsigned cpu_index)
 
 static int64_t virt_get_default_cpu_node_id(const MachineState *ms, int idx)
 {
-    return idx % ms->numa_state->num_nodes;
+    int64_t socket_id = ms->possible_cpus->cpus[idx].props.socket_id;
+
+    return socket_id % ms->numa_state->num_nodes;
 }
 
 static const CPUArchIdList *virt_possible_cpu_arch_ids(MachineState *ms)
-- 
2.25.1