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Subject: Re: [PATCH] x86/smpboot: Fix __max_logical_packages estimate
To: linux-kernel@vger.kernel.org
References: <1504722964-9170-1-git-send-email-prarit@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
        Jean Delvare <jdelvare@suse.com>, Borislav Petkov <bp@suse.de>,
        Andy Lutomirski <luto@kernel.org>,
        Tim Chen <tim.c.chen@linux.intel.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Michael Ellerman <mpe@ellerman.id.au>,
        =?UTF-8?B?VmlsbGUgU3lyasOkbMOk?= <ville.syrjala@linux.intel.com>
From: Prarit Bhargava <prarit@redhat.com>
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Date: Thu, 7 Sep 2017 17:18:23 -0400
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On 09/06/2017 02:36 PM, Prarit Bhargava wrote:
> A system booted with a small number of cores enabled per package
> panics because the estimate of __max_logical_packages is too low.
> This occurs when the total number of active cores across all packages
> is less than the maximum core count for a single package.
> 
> ie) On a 4 package system with 20 cores/package where only 4 cores
> are enabled on each package, the value of __max_logical_packages is
> calculated as DIV_ROUND_UP(16 / 20) = 1 and not 4.
> 
> Improve the estimate of __max_logical_packages by comparing the current
> estimate to the number of SMBIOS type 4 Processor Information structures.
> If __max_logical_packages is still insufficient during boot use the largest
> possible value of Package ID.

If I move this calculation to native_smp_cpus_done() I can eliminate a chunk
of code and use boot_cpu_data.booted_cores to get a correct value.

I'll resubmit with a new patch.

P.