linux-kernel - Re: [patch V3a 30/40] x86/cpu: Provide an AMD/HYGON specific topology parser

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Date:   Fri, 11 Aug 2023 19:11:05 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Pu Wen <pu_wen@...mail.com>, LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, Tom Lendacky <thomas.lendacky@....com>,
        Andrew Cooper <andrew.cooper3@...rix.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Huang Rui <ray.huang@....com>, Juergen Gross <jgross@...e.com>,
        Dimitri Sivanich <dimitri.sivanich@....com>,
        Michael Kelley <mikelley@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>
Subject: Re: [patch V3a 30/40] x86/cpu: Provide an AMD/HYGON specific
 topology parser

On Fri, Aug 11 2023 at 20:58, Pu Wen wrote:
> On 2023/8/3 3:51, Thomas Gleixner wrote:
>> +	if (tscan->c->x86_vendor == X86_VENDOR_AMD) {
>> +		if (tscan->c->x86 == 0x15)
>> +			tscan->c->topo.cu_id = leaf.cuid;
>> +
>> +		cacheinfo_amd_init_llc_id(tscan->c, leaf.nodeid);
>> +	} else {
>> +		/*
>> +		 * Package ID is ApicId[6..] on Hygon CPUs. See commit
>> +		 * e0ceeae708ce for explanation. The topology info is
>> +		 * screwed up: The package shift is always 6 and the node
>> +		 * ID is bit [4:5]. Don't touch the latter without
>> +		 * confirmation from the Hygon developers.
>> +		 */
>> +		topology_set_dom(tscan, TOPO_CORE_DOMAIN, 6, tscan->dom_ncpus[TOPO_CORE_DOMAIN]);
>
> Hygon updated CPUs will not always shift 6, and shift 6 is not good for 
> running guests.
> So suggest to modify like this:
>      if (!boot_cpu_has(X86_FEATURE_HYPERVISOR) && tscan->c->x86_model <= 
> 0x3)
>          topology_set_dom(tscan, TOPO_CORE_DOMAIN, 6, 
> tscan->dom_ncpus[TOPO_CORE_DOMAIN]);

This is exactly what the existing code does today. Can you please send a
delta patch on top of this with a proper explanation?

Thanks,

        tglx