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 20:58:00 +0800
From:   Pu Wen <pu_wen@...mail.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        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 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]);

-- 
Regards,
Pu Wen

> +		cacheinfo_hygon_init_llc_id(tscan->c);
> +	}
> +	return true;
> +}
> +