Re: [Xen-devel] [PATCH 1/2] add cpu_thread_id to struct cpuinfo_x86

[Juergen Gross <jgross@xxxxxxxx>]

On 03/09/18 15:46, Jan Beulich wrote:
>>>> On 31.08.18 at 18:22, <jgross@xxxxxxxx> wrote:
>> Add the thread-id to the cpu config data and an accessor macro
>> cpu_to_thread().
>>
>> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
>> ---
>>  xen/arch/x86/cpu/common.c       |  1 +
>>  xen/arch/x86/smpboot.c          | 10 ++++++++++
>>  xen/include/asm-arm/processor.h |  1 +
>>  xen/include/asm-x86/processor.h |  2 ++
>>  xen/include/public/sysctl.h     |  1 +
>>  5 files changed, 15 insertions(+)
>>
>> diff --git a/xen/arch/x86/cpu/common.c b/xen/arch/x86/cpu/common.c
>> index 057859ab14..f626a6a510 100644
>> --- a/xen/arch/x86/cpu/common.c
>> +++ b/xen/arch/x86/cpu/common.c
>> @@ -434,6 +434,7 @@ void identify_cpu(struct cpuinfo_x86 *c)
>>      c->phys_proc_id = XEN_INVALID_SOCKET_ID;
>>      c->cpu_core_id = XEN_INVALID_CORE_ID;
>>      c->compute_unit_id = INVALID_CUID;
>> +    c->cpu_thread_id = XEN_INVALID_THREAD_ID;
>>      memset(&c->x86_capability, 0, sizeof c->x86_capability);
>>  
>>      generic_identify(c);
>> diff --git a/xen/arch/x86/smpboot.c b/xen/arch/x86/smpboot.c
>> index 7e76cc3d68..2c6a40c543 100644
>> --- a/xen/arch/x86/smpboot.c
>> +++ b/xen/arch/x86/smpboot.c
>> @@ -247,6 +247,8 @@ static void set_cpu_sibling_map(unsigned int cpu)
>>      cpumask_set_cpu(cpu, per_cpu(cpu_core_mask, cpu));
>>      cpumask_set_cpu(cpu, per_cpu(cpu_sibling_mask, cpu));
>>  
>> +    c[cpu].cpu_thread_id = 0;
>> +
>>      if ( c[cpu].x86_num_siblings > 1 )
>>      {
>>          for_each_cpu ( i, &cpu_sibling_setup_map )
>> @@ -270,6 +272,14 @@ static void set_cpu_sibling_map(unsigned int cpu)
>>                         "CPU%u: unclear relationship with CPU%u\n",
>>                         cpu, i);
>>          }
>> +
>> +        for_each_cpu ( i, per_cpu(cpu_sibling_mask, cpu) )
>> +        {
>> +            if ( cpu == i )
>> +                break;
>> +            c[cpu].cpu_thread_id++;
> 
> No. This wants doing alongside setting of the other similar fields,
> i.e. in (at least) detect_extended_topology() and detect_ht(). It
> is the hardware which tells us what the thread ID is.

I wasn't able to find the related information for AMD cpus. In case it
is in the specs it is hidden very well.

> I think you also want to reset the new field in cpu_smpboot_free().

Ah yes, indeed!


Juergen


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