The IPMI document is expanded with a proposal to emulate BMC-side IPMI devices. This allows a QEMU instance running server software to interact with a different QEMU instance running BMC firmware, which should closely model how a real server system works.
The document as rendered by "make sphinxdocs" can be seen here: https://hskinnemoen.github.io/qemu/specs/ipmi.html Signed-off-by: Havard Skinnemoen <hskinnem...@google.com> --- docs/specs/ipmi.rst | 83 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 83 insertions(+) diff --git a/docs/specs/ipmi.rst b/docs/specs/ipmi.rst index e0f9ab20ba..f45a452ef9 100644 --- a/docs/specs/ipmi.rst +++ b/docs/specs/ipmi.rst @@ -91,6 +91,89 @@ further delegated to an external emulator, or a real BMC. The ``ipmi-bmc-extern`` device has a required ``chardev`` property which specifies the communications channel to the external BMC. +Baseband Management Controller (BMC) emulation +============================================== + +.. note:: This section is just a proposal. QEMU does not yet support BMC-side + IPMI emulation. + +This section is about emulation of IPMI-related devices in a System-on-Chip +(SoC) used as a Baseband Management Controller. This is not to be confused with +emulating the BMC device as seen by the main processor. + +SoCs that are designed to be used as a BMC often have dedicated hardware that +allows them to be connected to one or more of the IPMI System Interfaces. The +BMC-side hardware interface is not standardized, so each type of SoC may need +its own device implementation in QEMU, for example: + +* ``aspeed-ipmi-ibt`` for emulating the Aspeed iBT peripheral. +* ``npcm7xx-ipmi-kcs`` for emulating the Nuvoton NPCM7xx Host-to-BMC Keyboard + Controller Style (KCS) channels. + +.. blockdiag:: + + blockdiag bmc_ipmi { + orientation = portrait + default_group_color = "none"; + class responder [color = lightblue]; + class host [color = salmon]; + + host [color="aquamarine", label="External Host"] + + group { + orientation = portrait + + group { + orientation = portrait + + ipmi-responder [class = "responder"] + npcm7xx-ipmi-kcs [class = "responder", stacked] + + ipmi-responder <- npcm7xx-ipmi-kcs [hstyle = generalization]; + } + + group { + orientation = portrait + + ipmi-host [class = "host"]; + ipmi-host-sim [class = "host"]; + ipmi-host-extern [class = "host"]; + + ipmi-host <- ipmi-host-sim [hstyle = generalization]; + ipmi-host <- ipmi-host-extern [hstyle = generalization]; + } + + ipmi-responder <-> ipmi-host + } + + ipmi-host-extern <-> host [label="chardev"]; + } + +IPMI Responder +-------------- + +The software running on the BMC needs to intercept reads and writes to the +system interface registers on the main processor. This requires special +hardware that needs to be emulated by QEMU. We'll call these device *IPMI +responders*. + +All *IPMI responder* devices should implement the ``ipmi-responder`` interface +to allow an IPMI Host implementation to interact with them in a standard way. + +IPMI Host +--------- + +Mirroring the main processor emulation, the responder devices delegate +emulation of host behavior to a Host device that is a subclass of +``ipmi-host``. This type of device is called a Host because that's what it +looks like to the BMC guest software. + +The host behavior may be further delegated to an external emulator (e.g. +another QEMU VM) through the ``ipmi-host-extern`` host implementation. This +device has a required ``chardev`` property which specifies the communications +channel to the external host. The wire format is the same as for +``ipmi-bmc-extern``. + Wire protocol ============= -- 2.28.0.709.gb0816b6eb0-goog