Re: [RFC 0/3] QEMU as IPMI BMC emulator

[Corey Minyard <minyard@acm.org>]

On Mon, Sep 28, 2020 at 05:39:13PM -0700, Havard Skinnemoen via wrote:
> This series briefly documents the existing IPMI device support for main
> processor emulation, and goes on to propose a similar device structure to
> emulate IPMI responder devices in BMC machines. This would allow a qemu
> instance running BMC firmware to serve as an external BMC for a qemu instance
> running server software.
> 
> RFC only at this point because the series does not include actual code to
> implement this. I'd appreciate some initial feedback on
> 
> 1. Whether anyone else is interested in something like this.

Though I've had this idea once or twice, I'm not working on real BMCs,
so I didn't really pursue anything.  It's a good idea, I think, for the
BMC developers, and possibly for system developers trying to do
integration testing between BMCs and system software.

You will need to tie in to more emulation than just the BMC side of the
system interface registers.  You will also need to tie into GPIOs or
whatnot for things like host reset.

Power handling is going to be a bit weird.  The OpenIPMI emulator
starts/stops qemu based upon power control.  It might be possible to do
the same thing in this sort of emulator.

You may need extensions to the protocol, and that's fine.  I can't think
of any at the moment, but you never know.

> 2. Completeness (i.e. anything that could be explained in more detail in the
>    docs).

It's certainly a good start.  The second patch would be useful right
now.  There are more details, of course, but I think that's covered in
the man page under the various devices.

Thanks,

-corey

> 3. Naming, and whether 'specs' is the right place to put this.
> 4. Whether it's OK to enable the blockdiag sphinx extension (if not, I'll just
>    toss the block diagrams and turn the docs into walls of text).
> 
> If this seems reasonable, I'll start working with one of my team mates on
> implementing the common part, as well as the Nuvoton-specific responder device.
> Possibly also an Aspeed device.
> 
> Havard Skinnemoen (3):
>   docs: enable sphinx blockdiag extension
>   docs/specs: IPMI device emulation: main processor
>   docs/specs: IPMI device emulation: BMC
> 
>  docs/conf.py         |   5 +-
>  docs/specs/index.rst |   1 +
>  docs/specs/ipmi.rst  | 183 +++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 188 insertions(+), 1 deletion(-)
>  create mode 100644 docs/specs/ipmi.rst
> 
> -- 
> 2.28.0.709.gb0816b6eb0-goog
> 
>