Re: [Qemu-devel] [RFC PATCH 2/9][SeaBIOS] Implement acpi-dsdt functions for memory hotplug.

[Vasilis Liaskovitis]

Hi,

On Fri, Apr 20, 2012 at 12:55:24PM +0200, Igor Mammedov wrote:
> >+        /* Memory eject notify method */
> >+        OperationRegion(MEMJ, SystemIO, 0xaf40, 32)
> >+        Field (MEMJ, ByteAcc, NoLock, Preserve)
> >+        {
> >+            MPE, 256
> >+        }
> >+
> >+        Method (MPEJ, 2, NotSerialized) {
> >+            // _EJ0 method - eject callback
> >+            Store(ShiftLeft(1,Arg0), MPE)
> >+            Sleep(200)
> >+        }
> MPE is write only and only one memslot is ejected at a time. Why 256 
> bit-field is here then?
> Could we use just 1 byte and write a slot number into it and save some io 
> address space this way?

good point. This was implemented similarly to the hot-add/status register only
for symmetry, but you are right, since only one slot is ejected at a time, this
can be reduced to one byte and save space. I will update for the next version.

> 
> >+
> >+        /* Memory hotplug notify method */
> >+        OperationRegion(MEST, SystemIO, 0xaf20, 32)
> It's more a suggestion: move it a bit farther to allow maybe 1024 cpus in the 
> future.
> That will prevent compatibility a headache, if we decide to expand support to 
> more then
> 256 cpus.

ok, I will move it to 0xaf80 or higher (so cpu-hotplug could be extended to at
least 1024 cpus)

> 
> Or event better to make this address configurable in run-time and build this 
> var along
> with SSDT (converting along the way all other hard-coded io ports to the same 
> generic
> run-time interface). This wish is out of scope of this patch-set, but what
> do you think about the idea?

yes, that would give more flexibility and avoid more compatibility headaches.
As you say it's not a main issue for the series, but I can work on it as we 
start
converting hardcoded i/o ports to configurable properties.

thanks,

- Vasilis