Re: [PATCH v2 2/4] numa: Validate socket and NUMA node boundary if required

[Gavin Shan <gshan@redhat.com>]

On 2/23/23 8:05 PM, Philippe Mathieu-Daudé wrote:
> On 23/2/23 09:13, Gavin Shan wrote:
>> For some architectures like ARM64, multiple CPUs in one socket can't be
>> associated with different NUMA nodes. Otherwise, the guest kernel is confused
>> about the CPU topology. For example, the following warning message is observed
>> from linux guest with the below 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
>>
>> Improve the sitation to reject the configuration where multiple CPUs
> 
> Typo "situation".
> 

Yes, I will fix it up in next revision.

>> in one socket have been associated with different NUMA nodes. The
>> newly introduced helper set_numa_socket_boundary() is expected to
>> called by specific machines (boards) where the boundary is required.
>>
>> Signed-off-by: Gavin Shan <gshan@redhat.com>
>> ---
>>   hw/core/machine.c     | 34 ++++++++++++++++++++++++++++++++++
>>   hw/core/numa.c        |  7 +++++++
>>   include/sysemu/numa.h |  4 ++++
>>   3 files changed, 45 insertions(+)
> 
> 
>> diff --git a/include/sysemu/numa.h b/include/sysemu/numa.h
>> index 4173ef2afa..160008fff4 100644
>> --- a/include/sysemu/numa.h
>> +++ b/include/sysemu/numa.h
>> @@ -86,6 +86,9 @@ struct NumaState {
>>       /* Detect if HMAT support is enabled. */
>>       bool hmat_enabled;
>> +    /* CPUs in one socket can't break socket boundary */
>> +    bool have_socket_boundary;
> 
> This field belong to MachineClass, please add it as
> numa_have_socket_boundary just after to numa_mem_supported.
> 
> Next patches become:
> 
> ---
> diff --git a/hw/arm/sbsa-ref.c b/hw/arm/sbsa-ref.c
> index f778cb6d09..a48f1b2329 100644
> --- a/hw/arm/sbsa-ref.c
> +++ b/hw/arm/sbsa-ref.c
> @@ -864,6 +864,7 @@ static void sbsa_ref_class_init(ObjectClass *oc, void *data)
>       mc->possible_cpu_arch_ids = sbsa_ref_possible_cpu_arch_ids;
>       mc->cpu_index_to_instance_props = sbsa_ref_cpu_index_to_props;
>       mc->get_default_cpu_node_id = sbsa_ref_get_default_cpu_node_id;
> +    mc->numa_have_socket_boundary = true;
>   }
> ---
> 
> Otherwise LGTM :)
> 

Thanks, Philippe. It makes sense to have the field in MachineClass and the
changes will be included in next revision.

Thanks,
Gavin