On 08/19/2010 11:51 PM, Anthony Liguori wrote:
Neither approach maps well to real hardware. An x86 CPU cannot exist
without a local APIC and a local APIC cannot exist without an x86
CPU. The
two are fundamentally tied together.
What about 486? Or 82489?
Don't confuse the local APIC with the PIC or the I/O APIC.
The local APIC has always existed in the CPU core. There is also an I/O
APIC which exists outside of the CPU core. The local APIC was introduced
with SMP support.
In theory it's possible to have a discrete local APIC on the 486 or the
Pentium. See figure 5-1 in the Intel multiprocessor specification.
When you look at the local APIC (apic.c) however, you see that it's the
only device in the tree that actually interacts with a CPUState.
Even worse, it does it through an opaque pointer even though the only
CPUState that makes sense there is the i386 CPUState. (BTW, there is
exactly one other example of a CPUState property, and it's in the CRIS PIC).
Paolo
