Re: [PATCH] hw/arm/virt: Prevent CPUs in one socket to span mutiple NUMA nodes

[Gavin Shan <gshan@redhat.com>]

On 2/21/23 8:15 PM, Philippe Mathieu-Daudé wrote:
> On 21/2/23 09:53, Gavin Shan wrote:
>> Linux kernel guest reports warning when two CPUs in one socket have
>> been associated with different NUMA nodes, using the following command
>> lines.
>>
>>    -smp 6,maxcpus=6,sockets=2,clusters=1,cores=3,threads=1 \
>>    -numa node,nodeid=0,cpus=0-1,memdev=ram0                \
>>    -numa node,nodeid=1,cpus=2-3,memdev=ram1                \
>>    -numa node,nodeid=2,cpus=4-5,memdev=ram2                \
>>
>>    ------------[ cut here ]------------
>>    WARNING: CPU: 0 PID: 1 at kernel/sched/topology.c:2271 build_sched_domains+0x284/0x910
>>    Modules linked in:
>>    CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.14.0-268.el9.aarch64 #1
>>    pstate: 00400005 (nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>>    pc : build_sched_domains+0x284/0x910
>>    lr : build_sched_domains+0x184/0x910
>>    sp : ffff80000804bd50
>>    x29: ffff80000804bd50 x28: 0000000000000002 x27: 0000000000000000
>>    x26: ffff800009cf9a80 x25: 0000000000000000 x24: ffff800009cbf840
>>    x23: ffff000080325000 x22: ffff0000005df800 x21: ffff80000a4ce508
>>    x20: 0000000000000000 x19: ffff000080324440 x18: 0000000000000014
>>    x17: 00000000388925c0 x16: 000000005386a066 x15: 000000009c10cc2e
>>    x14: 00000000000001c0 x13: 0000000000000001 x12: ffff00007fffb1a0
>>    x11: ffff00007fffb180 x10: ffff80000a4ce508 x9 : 0000000000000041
>>    x8 : ffff80000a4ce500 x7 : ffff80000a4cf920 x6 : 0000000000000001
>>    x5 : 0000000000000001 x4 : 0000000000000007 x3 : 0000000000000002
>>    x2 : 0000000000001000 x1 : ffff80000a4cf928 x0 : 0000000000000001
>>    Call trace:
>>     build_sched_domains+0x284/0x910
>>     sched_init_domains+0xac/0xe0
>>     sched_init_smp+0x48/0xc8
>>     kernel_init_freeable+0x140/0x1ac
>>     kernel_init+0x28/0x140
>>     ret_from_fork+0x10/0x20
>>
>> Fix it by preventing mutiple CPUs in one socket to be associated with
>> different NUMA nodes.
>>
>> Reported-by: Yihuang Yu <yihyu@redhat.com>
>> Signed-off-by: Gavin Shan <gshan@redhat.com>
>> ---
>>   hw/arm/virt.c | 37 +++++++++++++++++++++++++++++++++++++
>>   1 file changed, 37 insertions(+)
>>
>> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
>> index ac626b3bef..e0af267c77 100644
>> --- a/hw/arm/virt.c
>> +++ b/hw/arm/virt.c
>> @@ -230,6 +230,39 @@ static bool cpu_type_valid(const char *cpu)
>>       return false;
>>   }
>> +static bool numa_state_valid(MachineState *ms)
>> +{
>> +    MachineClass *mc = MACHINE_GET_CLASS(ms);
>> +    NumaState *state = ms->numa_state;
>> +    const CPUArchIdList *possible_cpus = mc->possible_cpu_arch_ids(ms);
>> +    const CPUArchId *cpus = possible_cpus->cpus;
>> +    int len = possible_cpus->len, i, j;
>> +
>> +    if (!state || state->num_nodes <= 1 || len <= 1) {
>> +        return true;
>> +    }
>> +
>> +    for (i = 0; i < len; i++) {
>> +        for (j = i + 1; j < len; j++) {
>> +            if (cpus[i].props.has_socket_id &&
>> +                cpus[i].props.has_node_id &&
>> +                cpus[j].props.has_socket_id &&
>> +                cpus[j].props.has_node_id &&
>> +                cpus[i].props.socket_id == cpus[j].props.socket_id &&
>> +                cpus[i].props.node_id != cpus[j].props.node_id) {
>> +                error_report("CPU-%d and CPU-%d in socket-%ld have been "
>> +                             "associated with node-%ld and node-%ld",
>> +                             i, j, cpus[i].props.socket_id,
>> +                             cpus[i].props.node_id,
>> +                             cpus[j].props.node_id);
>> +                return false;
>> +            }
>> +        }
>> +    }
>> +
>> +    return true;
>> +}
>> +
>>   static void create_randomness(MachineState *ms, const char *node)
>>   {
>>       struct {
>> @@ -2040,6 +2073,10 @@ static void machvirt_init(MachineState *machine)
>>           exit(1);
>>       }
>> +    if (!numa_state_valid(machine)) {
>> +        exit(1);
>> +    }
> 
> Why restrict to the virt machine?
> 

We tried x86 machines and virt machine, but the issue isn't reproducible on x86 machines.
So I think it's machine or architecture specific issue. However, I believe RiscV should
have similar issue because linux/drivers/base/arch_topology.c is shared by ARM64 and RiscV.
x86 doesn't use the driver to populate its CPU topology.

Thanks,
Gavin