Re: [RFC PATCH v3 4/4] hw/arm/virt: Parse -smp cluster parameter in virt_smp_parse

["wangyanan (Y)" <wangyanan55@huawei.com>]

Hi Drew,

On 2021/5/17 17:12, Andrew Jones wrote:
> On Sun, May 16, 2021 at 06:32:28PM +0800, Yanan Wang wrote:
>> There is a separate function virt_smp_parse() in hw/virt/arm.c used
>> to parse cpu topology for the ARM machines. So add parsing of -smp
>> cluster parameter in it, then total number of logical cpus will be
>> calculated like: max_cpus = sockets * clusters * cores * threads.
>>
>> Note, we will assume multi-cluster in one socket is not supported
>> and default the value of clusters to 1, if it's not explicitly
>> specified in -smp cmdline.
>>
>> Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
>> ---
>>   hw/arm/virt.c | 32 ++++++++++++++++++--------------
>>   1 file changed, 18 insertions(+), 14 deletions(-)
>>
>> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
>> index 7de822e491..678d5ef36c 100644
>> --- a/hw/arm/virt.c
>> +++ b/hw/arm/virt.c
>> @@ -2642,8 +2642,8 @@ static int virt_kvm_type(MachineState *ms, const char *type_str)
>>    * with the -smp cmdlines when parsing them.
>>    *
>>    * We require that at least one of cpus or maxcpus must be provided.
>> - * Threads will default to 1 if not provided. Sockets and cores must
>> - * be either both provided or both not.
>> + * Clusters and threads will default to 1 if they are not provided.
>> + * Sockets and cores must be either both provided or both not.
>>    *
>>    * Note, if neither sockets nor cores are specified, we will calculate
>>    * all the missing values just like smp_parse() does, but will disable
>> @@ -2652,15 +2652,18 @@ static int virt_kvm_type(MachineState *ms, const char *type_str)
>>   static void virt_smp_parse(MachineState *ms, QemuOpts *opts)
>>   {
>>       VirtMachineClass *vmc = VIRT_MACHINE_GET_CLASS(ms);
>> +    VirtMachineState *vms = VIRT_MACHINE(ms);
>>   
>>       if (opts) {
>>           unsigned cpus = qemu_opt_get_number(opts, "cpus", 0);
>>           unsigned maxcpus = qemu_opt_get_number(opts, "maxcpus", 0);
>>           unsigned sockets = qemu_opt_get_number(opts, "sockets", 0);
>> +        unsigned clusters = qemu_opt_get_number(opts, "clusters", 0);
>>           unsigned cores = qemu_opt_get_number(opts, "cores", 0);
>>           unsigned threads = qemu_opt_get_number(opts, "threads", 0);
>>   
>> -        /* Default threads to 1 if not provided */
>> +        /* Default clusters and threads to 1 if not provided */
>> +        clusters = clusters > 0 ? clusters : 1;
>>           threads = threads > 0 ? threads : 1;
>>   
>>           if (cpus == 0 && maxcpus == 0) {
>> @@ -2676,13 +2679,13 @@ static void virt_smp_parse(MachineState *ms, QemuOpts *opts)
>>               cores = 1;
>>               if (cpus == 0) {
>>                   sockets = 1;
>> -                cpus = sockets * cores * threads;
>> +                cpus = sockets * clusters * cores * threads;
>>               } else {
>>                   maxcpus = maxcpus > 0 ? maxcpus : cpus;
>> -                sockets = maxcpus / (cores * threads);
>> +                sockets = maxcpus / (clusters * cores * threads);
>>               }
>>           } else if (sockets > 0 && cores > 0) {
>> -            cpus = cpus > 0 ? cpus : sockets * cores * threads;
>> +            cpus = cpus > 0 ? cpus : sockets * clusters * cores * threads;
>>               maxcpus = maxcpus > 0 ? maxcpus : cpus;
>>           } else {
>>               error_report("sockets and cores must be both provided "
>> @@ -2695,25 +2698,26 @@ static void virt_smp_parse(MachineState *ms, QemuOpts *opts)
>>               exit(1);
>>           }
>>   
>> -        if (sockets * cores * threads < cpus) {
>> +        if (sockets * clusters * cores * threads < cpus) {
>>               error_report("cpu topology: "
>> -                         "sockets (%u) * cores (%u) * threads (%u) < "
>> -                         "smp_cpus (%u)",
>> -                         sockets, cores, threads, cpus);
>> +                         "sockets (%u) * clusters (%u) * cores (%u) * "
>> +                         "threads (%u) < smp_cpus (%u)",
>> +                         sockets, clusters, cores, threads, cpus);
>>               exit(1);
>>           }
>>   
>> -        if (sockets * cores * threads != maxcpus) {
>> +        if (sockets * clusters * cores * threads != maxcpus) {
>>               error_report("cpu topology: "
>> -                         "sockets (%u) * cores (%u) * threads (%u) "
>> -                         "!= maxcpus (%u)",
>> -                         sockets, cores, threads, maxcpus);
>> +                         "sockets (%u) * clusters (%u) * cores (%u) * "
>> +                         "threads (%u) != maxcpus (%u)",
>> +                         sockets, clusters, cores, threads, maxcpus);
>>               exit(1);
>>           }
>>   
>>           ms->smp.cpus = cpus;
>>           ms->smp.max_cpus = maxcpus;
>>           ms->smp.sockets = sockets;
>> +        vms->smp_clusters = clusters;
>>           ms->smp.cores = cores;
>>           ms->smp.threads = threads;
>>       }
>> -- 
>> 2.19.1
>>
> After reworking "[RFC PATCH v3 9/9] hw/arm/virt: Add separate -smp parsing
> function for ARM machines", this should also be reworked and fully tested,
> possibly using a standalone test, as as I suggested in the other review.
Ok, I will make full test.

Thanks,
Yanan
> Thanks,
> drew
>
> .