linux-kernel - Re: [PATCH] arch/x86: Remove second call to topology_update_package

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Message-ID: <1476310004.4440.16.camel@linux.intel.com>
Date:   Wed, 12 Oct 2016 15:06:44 -0700
From:   Tim Chen <tim.c.chen@...ux.intel.com>
To:     Prarit Bhargava <prarit@...hat.com>, linux-kernel@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Len Brown <len.brown@...el.com>, Borislav Petkov <bp@...e.de>,
        Andi Kleen <ak@...ux.intel.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Jiri Olsa <jolsa@...hat.com>
Subject: Re: [PATCH] arch/x86: Remove second call to
 topology_update_package_map()

On Wed, 2016-10-12 at 16:54 -0400, Prarit Bhargava wrote:
> 
> On 10/12/2016 03:51 PM, Tim Chen wrote:
> > 
> > On Wed, 2016-10-12 at 11:06 -0400, Prarit Bhargava wrote:
> > > 
> > > 
> > > On 10/12/2016 10:36 AM, Prarit Bhargava wrote:
> > > > 
> > > > 
> > > > This was noticed during the investigation of
> > > > 
> > > > http://git.kernel.org/tip/2a51fe083eba7f99cbda72f5ef90cdf2f4df882c
> > > > 
> > > > A note for reviewers on the cleanup in smp_init_package_map(): The
> > > > per_cpu variable x86_bios_cpu_apicid is initialized to BAD_APICID, and the
> > > > bitmaps are set to false by default so the code isn't necessary.  The
> > > > pr_warn() can also be dropped as generic_processor_info() will do a
> > > > pr_warning() in the same situation.
> > > > 
> > > > 
> > > > 
> > > > P.
> > > > 
> > > > -----8<-----
> > > > 
> > > > After commit 1f12e32f4cd5 ("x86/topology: Create logical package id"),
> > > > topology_update_package_map() is called twice on a CPU.  The first call is in
> > > > generic_processor_info(), which is called on all present cpus (found in either
> > > > mptable or ACPI MADT).  The second call is in smp_init_package_map() which
> > > > is called later on in the init sequence.
> > > > 
> > > > Only a single call is necessary for the kernel to initialize the data
> > > > structures properly. This patch drops the later call in smp_init_package_map()
> > > > and moves smp_init_package_map() out of smp_store_boot_cpu_info().
> > > > 
> > > Self-NAK.
> > > 
> > > This seems to not work on systems with an empty socket :/.  Looking into this now.
> > > 
> > > P.
> > My single node workstation also failed to boot with the patch.
> The patch is incorrect.  I'm dropping it completely.
> 

The call from generic_processor_info to topology_update_package_map
during early boot was essentially no op, as physical_package_map has
not have been allocated by smp_init_package_map yet.

We have to call topology_update_package_map in smp_init_package_map
after allocating physical_package_map to properly set up
physical_package_map.

Tim