On Sat, Jan 30, 2010 at 04:14:29AM +0800, Liu, Jinsong wrote:
Gleb Natapov wrote:
OK. Let me try to explain it one more time. Currently MADT table resides in memory of type "ACPI DATA" and AML code reads and writes this memory during CPU hot-plug. According to ACPI spec "ACPI DATA" ares can be reused by an OS, so consider what will happen if OS puts its data into memory area where MADT was and later gets cpu hotplug event. Do you see the problem now?
I just hesitate ' if OS puts its data ...'.
What is not clear here? OS is free to reuse this memory for whatever it wants.
Per my understanding, os will not write madt after booting, only AML write madt when necessary (i.e. cpu hotplug).
Your understanding is wrong. Read spec.
So is it necessary to mark madt as ACPI NVS?
ACPI VNS or reserved. The difference is that OS should save/restore ACPI NVS memory during S4 transition. Read the spec it is all there.
-- Gleb.