RE: [patch v2 28/38] x86/cpu: Provide an AMD/HYGON specific topology parser

[Thomas Gleixner]

On Sun, Jul 30 2023 at 05:20, Michael Kelley wrote:
> From: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Sent: Friday, July 28, 2023 5:13 AM
>> +	/*
>> +	 * If leaf 0xb is available, then SMT shift is set already. If not
>> +	 * take it from ecx.threads_per_cpu and use topo_update_dom() as
>
> "take it from ebx.threads_per_cu and use topology_update_dom() as"
>
>> +	 * topology_set_dom() would propagate and overwrite the already
>> +	 * propagated CORE level.
>> +	 */
>> +	if (!has_0xb) {
>> +		topology_update_dom(tscan, TOPO_SMT_DOMAIN, get_count_order(leaf.threads_per_cu),
>> +				    leaf.threads_per_cu);
>
> leaf.threads_per_cu needs to be (leaf.threads_per_cu + 1) above.  If
> the core has two hyper-threads, the value of the threads_per_cu
> field returned by CPUID is "1".
>
> All my Hyper-V VMs on AMD processors were coming up with only
> one thread per core.   The change fixes the problem.

You are right. Thanks for tracking that down!

    tglx