linux-kernel - RE: [patch v2 21/38] x86/cpu: Provide cpu_init/parse

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Message-ID: <87fs53n6xd.ffs@tglx>
Date:   Mon, 31 Jul 2023 22:48:46 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     "Michael Kelley (LINUX)" <mikelley@...rosoft.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        Andrew Cooper <andrew.cooper3@...rix.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        Dick Kennedy <dick.kennedy@...adcom.com>,
        James Smart <james.smart@...adcom.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        Guenter Roeck <linux@...ck-us.net>,
        "linux-hwmon@...r.kernel.org" <linux-hwmon@...r.kernel.org>,
        Jean Delvare <jdelvare@...e.com>,
        Huang Rui <ray.huang@....com>, Juergen Gross <jgross@...e.com>,
        Steve Wahl <steve.wahl@....com>,
        Mike Travis <mike.travis@....com>,
        Dimitri Sivanich <dimitri.sivanich@....com>,
        Russ Anderson <russ.anderson@....com>
Subject: RE: [patch v2 21/38] x86/cpu: Provide cpu_init/parse_topology()

On Mon, Jul 31 2023 at 16:10, Michael Kelley wrote:
> From: Thomas Gleixner <tglx@...utronix.de> Sent: Monday, July 31, 2023 8:38 AM
> The VM is an F72s_v2 in Azure running your patch set.  The VM has
> 72 vCPUs in two NUMA nodes across two physical Intel processors, with
> 36 vCPUs in each NUMA node.
>
> The output is from /sys/kernel/debug/x86/topo/cpus, so the initial_apicid
> is from CPUID, while the apicid is from read_apic_id() and matches the
> MADT.  As expected, the two values match for the first 36 vCPUs, but differ
> by 28 (decimal) for the remaining 36.
>
> initial_apicid:      0 apicid:              0
...
> initial_apicid:      23 apicid:              23

> initial_apicid:      40 apicid:              24
...
> initial_apicid:      63 apicid:              47

Is there any indication in some other CPUID leaf which lets us deduce this
wreckage?

I don't think the hypervisor space (0x40000xx) has anything helpful, but
staring at the architectural ones provided by hyper-V to the guest might
give us an hint. Can you provide a cpuid dump for the boot CPU please?

Thanks,

        tglx