linux-kernel - Re: [PATCH v5 1/4] x86/cpu/topology: Always try cpu_parse_topology

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Message-ID: <e4a791dd-5189-4f32-a229-fa93ec9d9d5d@amd.com>
Date: Thu, 11 Sep 2025 11:36:30 +0530
From: K Prateek Nayak <kprateek.nayak@....com>
To: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
	Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>,
	Jonathan Corbet <corbet@....net>, <x86@...nel.org>
CC: Naveen rao <naveen.rao@....com>, Sairaj Kodilkar <sarunkod@....com>, "H.
 Peter Anvin" <hpa@...or.com>, "Peter Zijlstra (Intel)"
	<peterz@...radead.org>, "Xin Li (Intel)" <xin@...or.com>, Pawan Gupta
	<pawan.kumar.gupta@...ux.intel.com>, <linux-kernel@...r.kernel.org>,
	<kvm@...r.kernel.org>, Mario Limonciello <mario.limonciello@....com>,
	"Gautham R. Shenoy" <gautham.shenoy@....com>, Babu Moger
	<babu.moger@....com>, Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
	<stable@...r.kernel.org>, Naveen N Rao <naveen@...nel.org>
Subject: Re: [PATCH v5 1/4] x86/cpu/topology: Always try
 cpu_parse_topology_ext() on AMD/Hygon

On 9/11/2025 10:07 AM, K Prateek Nayak wrote:
>  		/*
> -		 * In case leaf B is available, use it to derive
> -		 * topology information.
> +		 * If the extended topology leaf 0xb leaf doesn't exits,
> +		 * derive CORE and DIE information from the 0x8000001e leaf.
>  		 */
> -		err = detect_extended_topology(c);
> -		if (!err)
> -			c->x86_coreid_bits = get_count_order(c->x86_max_cores);
> +		if (!has_extended_topology) {
> +			c->cpu_die_id  = ecx & 0xff;

Just noticed that we still need that "cpu_die_id" from 0x8000001e since
0xb on AMD does not implement the LEVEL_TYPE of DIE_TYPE (5).

> +
> +			if (c->x86 >= 0x17) {
> +				c->cpu_core_id = ebx & 0xff;
> +
> +				if (smp_num_siblings > 1)
> +					c->x86_max_cores /= smp_num_siblings;
> +			}
> +		}

-- 
Thanks and Regards,
Prateek