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From: John Baldwin <jhb@freebsd.org>
To: freebsd-acpi@freebsd.org
Subject: Re: ACPI MADT BSP Details
Date: Fri, 12 Jul 2013 16:50:41 -0400
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 (bigwig.baldwin.cx); Fri, 12 Jul 2013 16:51:40 -0400 (EDT)
Cc: Rohit Athavale <rathaval@uci.edu>
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On Wednesday, July 10, 2013 7:48:42 pm Rohit Athavale wrote:
> Hi Folks,
> 
> I have two questions about discovering the processors from the MADT table.
> 
> Firstly,
> Can we find out which processor is the BSP from the MADT tables?
> When comparing the userland mptable binary's output versus acpidump's
> output I noticed that mptable informs us about which processor is the BSP
> and which are AP's .
> However I did not see this in the MADT tables.
> Is there a way to find out which processor is the BSP by means of any of
> the ACPI tables.

Nope.  You can read the local APIC ID of the current CPU during your bootstrap 
though.

> Secondly,
> Can we write into /dev/mem to say update the contents of MPTable with
> values that are non -default. I plan to read some values from the ACPI
> tables and update the MP tables.
> Is the /dev/mem/ file composed of physical addresses for user space memory
> ? I know this may not qualify as the correct place to ask,but I guess acpi
> list might have an answer to this.

Yes, you can likely do this.

-- 
John Baldwin