Re: [PATCH] cpu hotplug issue

Jan Kiszka
2011-08-04T08:40:12Z

On 2011-08-04 10:01, Gleb Natapov wrote:
> On Wed, Aug 03, 2011 at 06:25:07PM +0200, Vasilis Liaskovitis wrote:
>> On Wed, Aug 03, 2011 at 12:42:11PM +0200, Jan Kiszka wrote:
>>>>> Why can't Seabios read to true number online CPUs from the PIIX4 device?
>>>>> The information is there already, no need for addition PV here.
>>>>>
>>>> Where is it in PIIX4 device?
>>>
>>> PROC registers (or however they are called).
>>
>> In qemu-kvm, the cpus_sts bitmap array in PIIX4PMState/ACPIGPE has the true
>> number of online CPUS. This is accessed from the DSDT hotplug method in Seabios
>> as "OperationRegion SystemIO" with address 0xaf00. Is this i/o address in the
>> piix4 spec? How can it be accessed from the rest of SeaBIOS? It seems to reside
>> in ACPI_PM space.
>>
> 0xaf00 is not part of PIIX4. PIIX4 supports nor cpu host plug
> neither pci hot plug. I haven't found any PROC register in PIIX4 spec
> so far.

So it is some "board" extension that is declared to BIOS/OS via ACPI? In
any case, the channel we need to read the number of online CPUs already
exists.

Jan

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