[SeaBIOS] Alt SeaBIOS SSDT cpu hotplug

[Kevin O'Connor]

On Thu, Jul 08, 2010 at 03:54:10PM +0300, Gleb Natapov wrote:
> On Wed, Jul 07, 2010 at 07:26:07PM -0400, Kevin O'Connor wrote:
> > On Wed, Jul 07, 2010 at 01:22:49PM +0300, Gleb Natapov wrote:
> > > On Wed, Jul 07, 2010 at 12:57:05AM -0400, Kevin O'Connor wrote:
> > > > The "CPUS" package stores references to the Processor objects, and the
> > > > "CPON" package stores the state of which cpus are active.  With this
> > > > info, hopefully there is no need to update the MADT tables.
> > > > 
> > > The way you wrote it acpi_id is always equal to lapic_id which is not
> > > alway true. By using MADT from memory we remove this dependency from
> > > DSDT code.
> > 
> > The current code always sets the apic->processor_id equal to
> > apic->local_apic_id in the madt apic table.  If this changes, we could
> > add a dynamically created mapping table to the ssdt.  Something like:
> > 
> > Name(CPLA, Package() { 0x00, 0x01, 0x02, 0x03, 0x04 })
> > 
> Yeah, but if we can avoid it in the first place why not doing so.

There is a cost to reading/writing the MADT tables.  The hardcoding of
0x514 has a risk - it's not clear to me that an optionrom wont clobber
that space.  It also recently occurred to me that there may be a
problem if a guest expects the MADT address to remain constant across
a hibernate/restore cycle - the malloc_high() function doesn't
guarentee stable addresses across reboots.

>BTW how
> do you pass to DSDT what cpus are initially on? Previously this info was
> taken from memory copy of MADT too.

The CPON array is dynamically generated with the status of the
processors.  (It is then kept up to date by the DSDT code.)  The code
for generating CPON is:

    // build "Name(CPON, Package() { One, One, ..., Zero, Zero, ... })"
    *(ssdt_ptr++) = 0x08; // NameOp
    *(ssdt_ptr++) = 'C';
    *(ssdt_ptr++) = 'P';
    *(ssdt_ptr++) = 'O';
    *(ssdt_ptr++) = 'N';
    *(ssdt_ptr++) = 0x12; // PackageOp
    ssdt_ptr = encodeLen(ssdt_ptr, 2+1+(1*acpi_cpus), 2);
    *(ssdt_ptr++) = acpi_cpus;
    for (i=0; i<acpi_cpus; i++)
        *(ssdt_ptr++) = (i < CountCPUs) ? 0x01 : 0x00;

-Kevin