Hi Gavin,
On 2022/3/3 11:11, Gavin Shan wrote:
The default CPU-to-NUMA association is given by mc->get_default_cpu_node_id()
when it isn't provided explicitly. However, the CPU topology isn't fully
considered in the default association and it 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 populating the CPU topology in
virt_possible_cpu_arch_ids()
and considering the socket index when default CPU-to-NUMA association is given
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.
It may be better to split this patch into two. One extends
virt_possible_cpu_arch_ids,
and the other fixes the numa node ID issue.
Signed-off-by: Gavin Shan <gs...@redhat.com>
---
hw/arm/virt.c | 17 ++++++++++++++++-
1 file changed, 16 insertions(+), 1 deletion(-)
diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 46bf7ceddf..dee02b60fc 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -2488,7 +2488,9 @@ 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)
@@ -2496,6 +2498,7 @@ static const CPUArchIdList
*virt_possible_cpu_arch_ids(MachineState *ms)
int n;
unsigned int max_cpus = ms->smp.max_cpus;
VirtMachineState *vms = VIRT_MACHINE(ms);
+ MachineClass *mc = MACHINE_GET_CLASS(vms);
if (ms->possible_cpus) {
assert(ms->possible_cpus->len == max_cpus);
@@ -2509,6 +2512,18 @@ static const CPUArchIdList
*virt_possible_cpu_arch_ids(MachineState *ms)
ms->possible_cpus->cpus[n].type = ms->cpu_type;
ms->possible_cpus->cpus[n].arch_id =
virt_cpu_mp_affinity(vms, n);
+
+ ms->possible_cpus->cpus[n].props.has_socket_id = true;
+ ms->possible_cpus->cpus[n].props.socket_id =
+ n / (ms->smp.dies * ms->smp.clusters *
+ ms->smp.cores * ms->smp.threads);
+ if (mc->smp_props.dies_supported) {
+ ms->possible_cpus->cpus[n].props.has_die_id = true;
+ ms->possible_cpus->cpus[n].props.die_id =
+ n / (ms->smp.clusters * ms->smp.cores * ms->smp.threads);
+ }
I still don't think we need to consider dies if it's certainly not
supported yet, IOW, we will never come into the if-branch.
We are populating arm-specific topo info instead of the generic,
we can probably uniformly update this part together with other
necessary places when we decide to support dies for arm virt
machine in the future. :)
