Re: [Xen-devel] [PATCH] Supporting reading of system information from BIOS.

[Matt Wilson <msw@xxxxxxxxx>]

On Tue, Oct 14, 2014 at 10:14:07AM +0530, Rita Sinha wrote:
>
> This patch is in response to
> http://wiki.xenproject.org/wiki/Outreach_Program_Projects#CPU.2FRAM.2FPCI_diagram_tool
> project for applying to OPW-Round9.It adds support for reading
> system architecture information from BIOS rather than from sysfs and
> proc interfaces since in a virtualisation enviroment, some of this
> information is no longer accurate, particularly any information
> based around numbers of cpus.

Nice, thanks for taking this project on.

Have you considered implementing something that functions the same as
hwloc-gather-topology(1):
  http://manpages.ubuntu.com/manpages/saucy/man1/hwloc-gather-topology.1.html

but instead of collecting information from /proc and /sys, it accesses
DMI and ACPI tables directly? This would let you reuse the existing
lstopo(1) command to display a graphical topology.

--msw

> ---
>  dmidecode.pl | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 51 insertions(+)
>  create mode 100644 dmidecode.pl
> 
> diff --git a/dmidecode.pl b/dmidecode.pl
> new file mode 100644
> index 0000000..76fdf78
> --- /dev/null
> +++ b/dmidecode.pl
> @@ -0,0 +1,51 @@
> +#!/usr/bin/perl
> +
> +# dmidecode.pl - a script to read the system architecture information
> +# directly from the BIOS.  Only for Linux.
> +#
> +# Rita Sinha (rita.sinha89@xxxxxxxxx)
> +# OPW Program-Round9
> +# 14/10/14
> +
> +`id -u` == 0 || die "must be run as root";
> +
> +open(DmiFh, "/usr/sbin/dmidecode |") or
> +  die "problem running dmidecode";
> +$DmiNumProcs = 0;
> +$DmiNumSockets = 0;
> +while(<DmiFh>)
> +  {
> +    next unless /Central Processor/;
> +    # We've found a processor (or at least a socket), keep going
> +    while(<DmiFh>)
> +     {
> +       # Keep walking the dmidecode output to find out if
> +       # the socket has a processor in it.
> +       last if /^Handle/;
> +       next unless /Status/;
> +       $DmiNumSockets += 1;
> +       /Populated/ and $DmiNumProcs += 1;
> +       last;
> +     }
> +  }
> +close DmiFh;
> +
> +open(CpuInfoFh, "/proc/cpuinfo") || die "failed to open /proc/cpuinfo!";
> +$CpuInfoNumProcs = 0;
> +while(<CpuInfoFh>)
> +  {
> +    next unless /^processor.*:/;
> +    ($CpuInfoNumProcs) += (/^processor.*: (\d+)/);
> +  }
> +close CpuInfoFh;
> +
> +if ( $DmiNumProcs != $CpuInfoNumProcs )
> +  {
> +    print "Warning: dmidecode reports $DmiNumProcs processors, kernel 
> reports $CpuInfoNumProcs processors.\n";
> +  }
> +
> +if ( $DmiNumProcs != $DmiNumSockets )
> +  {
> +    print "Info: dmidecode reports $DmiNumSockets cpu sockets, but only 
> $DmiNumProcs processors.\n";
> +  }

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