ACPI MADT BSP Details

[Rohit Athavale]

Thanks John.

After reading into details of the ACPI spec, it is also said in the spec
that the first processor APIC entry also happens to be the BSP . It is
expected the BSP always be kept the first entry in processor APIC's.

Best Regards,
 Rohit *A*thavale





On Fri, Jul 12, 2013 at 1:50 PM, John Baldwin <jhb at freebsd.org> wrote:

> 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
>