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

[Juergen Gross <jgross@xxxxxxxx>]

On 03/09/18 16:47, Jan Beulich wrote:
>>>> On 03.09.18 at 15:53, <jgross@xxxxxxxx> wrote:
>> 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.
> 
> What was used for compute units in Fam16 and earlier is used for
> hyperthreads in Fam17 (and going forward, from what iirc Brian
> has said).

And what about hyperthreads in Fam16 and earlier? Or are "compute units"
just another name for the threads and I can rename that field?


Juergen


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