Re: IPMI Smbus

[Corey Minyard <minyard@acm.org>]

On Tue, Apr 06, 2021 at 10:06:09AM -0700, Patrick Venture wrote:
> On Tue, Apr 6, 2021 at 9:54 AM Corey Minyard <cminyard@mvista.com> wrote:
> >
> > On Tue, Apr 06, 2021 at 09:04:35AM -0700, Patrick Venture wrote:
> > > Corey;
> > >
> > > I saw you have a branch that is working on adding smbus IPMI support
> > > (the ssif approach).
> > >
> > > Can you provide details on the status of this work?
> >
> > There is already an SMBus BMC device that can sit on the I2C bus.  It's
> > in mainstream qemu now.
> 
> This device:
> 
> github.com/qemu/qemu/blob/master/hw/ipmi/smbus_ipmi.c
> 
> So this device gets added to the BMC's i2c, and it's just that there's
> no host-side support to then master this device?  in a multi-node
> simulation.

This works two ways, there is an internal, simple BMC simulator, or it
can make a connection to an external BMC.

> 
> I'm asking because my team is currently working on implementing ssif
> support (between two nodes).

Ah, there is already a protocol that I developed for this that others
are using already.  At Google I think, among others.  It's described in:
https://sourceforge.net/p/openipmi/code/ci/master/tree/lanserv/README.vm

The rest of that directory is a BMC simulator that can connect to qemu
and manage a qemu session, starting, stopping, monitoring, etc.  The
idea was to use IPMI to manage qemu, and some people are using it for
that.

There is obviously already a bridge on the host side to handle taking
the SSIF messages and transporting them over the wire to something else.
I know people were working on the BMC side, but I don't know the status.

-corey

> 
> >
> > It does not have smbus alert support, though.  I have patches for that,
> > but qemu doesn't have a flexibly general interrupt infrastructure, so I
> > hacked something in, and it's likely to be contentious.  The trouble is
> > that the interrupt is disconnected from any real device, and qemu
> > doesn't handle that very well.  And like the other things, I really only
> > created it for my testing.
> >
> > For doing what you are trying to do, I don't think you need any special
> > support on either side for SSIF to work.
> >
> > -corey
> >
> > >
> > > Patrick
>