Re: [Qemu-devel] [PATCH 3/4] PowerPC 440EP SoC emulation

[Hollis Blanchard]

On Tue, 2008-12-16 at 11:45 +0100, Aurelien Jarno wrote:
> On Mon, Dec 15, 2008 at 06:17:31PM -0600, Hollis Blanchard wrote:
> > Wire up the system-on-chip devices present on 440EP chips.
> > 
> > This patch is a little unusual in that qemu doesn't actually emulate the 440
> > core, but we use this board code with KVM (which does). If/when 440 core
> > emulation is supported, the kvm_enabled() hack can be removed.
> > 
> 
> What are the mains differences between 405 and 440 cores? Would it be
> easy to add support for 440 core in QEMU?

It's been a while since I programmed for the 405, but from memory:

Unlike the 405, the 440 is a Book E core. The biggest difference is that
there is no real mode; MMU translation is always active. MSR[IR] and DR
have been replaced with IS and DS, and those "address space" bits
contribute to the 41-bit virtual address (32-bit effective, 8-bit PID
like 405, 1-bit AS). The TLB organization is pretty much the same as 405
(64-entry fully associative), though the data in each entry has changed
a little.

Fixed interrupt vectors have been replaced with programmable ones, via
the IVPR base register and 16 IVOR registers, indicating the offset of
each vector from IVPR.

There is a Application Note that more fully lists the software
differences:
https://www.amcc.com/MyAMCC/retrieveDocument/PowerPC/440GP/PPC440GP_AN2020_SWC405GP.pdf
Because the MMU is always on, tlbia doesn't exist any more. There are a
few other minor instruction and register changes.

As I've mentioned, most 440 peripherals are the same or similar to 405,
which is definitely helpful.

-- 
Hollis Blanchard
IBM Linux Technology Center