Re: [PATCH v5 2/4] hw/arm/virt: Consider SMP configuration in CPU topology

[Gavin Shan <gshan@redhat.com>]

Hi Yanan,

On 4/14/22 10:49 AM, wangyanan (Y) wrote:
> On 2022/4/14 10:37, Gavin Shan wrote:
>> On 4/14/22 10:27 AM, wangyanan (Y) wrote:
>>> On 2022/4/14 8:08, Gavin Shan wrote:
>>>> On 4/13/22 8:39 PM, wangyanan (Y) wrote:
>>>>> On 2022/4/3 22:59, Gavin Shan wrote:
>>>>>> Currently, the SMP configuration isn't considered when the CPU
>>>>>> topology is populated. In this case, it's impossible to provide
>>>>>> the default CPU-to-NUMA mapping or association based on the socket
>>>>>> ID of the given CPU.
>>>>>>
>>>>>> This takes account of SMP configuration when the CPU topology
>>>>>> is populated. The die ID for the given CPU isn't assigned since
>>>>>> it's not supported on arm/virt machine yet.
>>>>>>
>>>>>> Signed-off-by: Gavin Shan <gshan@redhat.com>
>>>>>> ---
>>>>>>   hw/arm/virt.c | 16 +++++++++++++++-
>>>>>>   1 file changed, 15 insertions(+), 1 deletion(-)
>>>>>>
>>>>>> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
>>>>>> index d2e5ecd234..3174526730 100644
>>>>>> --- a/hw/arm/virt.c
>>>>>> +++ b/hw/arm/virt.c
>>>>>> @@ -2505,6 +2505,7 @@ 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);
>>>>>> @@ -2518,8 +2519,21 @@ 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);
>>>>>> +
>>>>>> +        assert(!mc->smp_props.dies_supported);
>>>>>> + ms->possible_cpus->cpus[n].props.has_socket_id = true;
>>>>>> +        ms->possible_cpus->cpus[n].props.socket_id =
>>>>>> +            (n / (ms->smp.clusters * ms->smp.cores * ms->smp.threads)) %
>>>>>> +            ms->smp.sockets;
>>>>> No need for "% ms->smp.sockets".
>>>>
>>>> Yeah, lets remove it in v6.
>>>>
>>>>>> + ms->possible_cpus->cpus[n].props.has_cluster_id = true;
>>>>>> +        ms->possible_cpus->cpus[n].props.cluster_id =
>>>>>> +            (n / (ms->smp.cores * ms->smp.threads)) % ms->smp.clusters;
>>>>>> + ms->possible_cpus->cpus[n].props.has_core_id = true;
>>>>>> +        ms->possible_cpus->cpus[n].props.core_id =
>>>>>> +            (n / ms->smp.threads) % ms->smp.cores;
>>>>>> ms->possible_cpus->cpus[n].props.has_thread_id = true;
>>>>>> -        ms->possible_cpus->cpus[n].props.thread_id = n;
>>>>>> +        ms->possible_cpus->cpus[n].props.thread_id =
>>>>>> +            n % ms->smp.threads;
>>>>>>       }
>>>>>>       return ms->possible_cpus;
>>>>>>   }
>>>>> Otherwise, looks good to me:
>>>>> Reviewed-by: Yanan Wang <wangyanan55@huawei.com>
>>>>>
>>>>
>>>> Thanks for your time to review :)
>>>>
>>>>
>>> Oh, after further testing this patch breaks numa-test for aarch64,
>>> which should be checked and fixed. I guess it's because we have
>>> more IDs supported for ARM. We have to fully running the QEMU
>>> tests before sending some patches to ensure that they are not
>>> breaking anything. :)
>>>
>>
>> Thanks for catching the failure and reporting back. I'm not
>> too much familar with QEMU's test workframe. Could you please
>> share the detailed commands to reproduce the failure? I will
>> fix in v6, which will be done in a separate patch :)
>>
> There is a reference link: https://wiki.qemu.org/Testing
> To catch the failure of this patch: "make check" will be enough.
> 

Thanks for the pointer. The issue is caused by ms->possible_cpus->cpus[n].props.thread_id.
Before this patch, it's value of [0 ... smp.cpus]. However, it's always zero
after this patch is applied because '%' operation is applied for the thread
ID.

What we need to do is to specify SMP configuration for the test case. I will
add PATCH[v6 5/5] for it.

diff --git a/tests/qtest/numa-test.c b/tests/qtest/numa-test.c
index 90bf68a5b3..6178ac21a5 100644
--- a/tests/qtest/numa-test.c
+++ b/tests/qtest/numa-test.c
@@ -223,7 +223,7 @@ static void aarch64_numa_cpu(const void *data)
      QTestState *qts;
      g_autofree char *cli = NULL;
  
-    cli = make_cli(data, "-machine smp.cpus=2 "
+    cli = make_cli(data, "-machine smp.cpus=2,smp.sockets=1,smp.cores=1,smp.threads=2 "

Thanks,
Gavin