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Re: [PATCH 2/8] docs/specs: IPMI device emulation: main processor
From: |
Corey Minyard |
Subject: |
Re: [PATCH 2/8] docs/specs: IPMI device emulation: main processor |
Date: |
Thu, 9 Sep 2021 18:48:01 -0500 |
On Thu, Sep 09, 2021 at 04:06:14PM -0700, Hao Wu wrote:
> From: Havard Skinnemoen <hskinnemoen@google.com>
>
> This document is an attempt to briefly document the existing IPMI
> emulation support on the main processor. It provides the necessary
> background for the BMC-side IPMI emulation proposed by the next patch.
I'm good with this for the most part. One nit inline below.
This block diagrams depend on the previous patch.
>
> Signed-off-by: Havard Skinnemoen <hskinnemoen@google.com>
> Signed-off-by: Hao Wu <wuhaotsh@google.com>
> ---
> docs/specs/index.rst | 1 +
> docs/specs/ipmi.rst | 100 +++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 101 insertions(+)
> create mode 100644 docs/specs/ipmi.rst
>
> diff --git a/docs/specs/index.rst b/docs/specs/index.rst
> index 65e9663916..1b5d177d53 100644
> --- a/docs/specs/index.rst
> +++ b/docs/specs/index.rst
> @@ -11,6 +11,7 @@ guest hardware that is specific to QEMU.
> ppc-spapr-xive
> ppc-spapr-numa
> acpi_hw_reduced_hotplug
> + ipmi
> tpm
> acpi_hest_ghes
> acpi_cpu_hotplug
> diff --git a/docs/specs/ipmi.rst b/docs/specs/ipmi.rst
> new file mode 100644
> index 0000000000..adb098b53d
> --- /dev/null
> +++ b/docs/specs/ipmi.rst
> @@ -0,0 +1,100 @@
> +=====================
> +IPMI device emulation
> +=====================
> +
> +QEMU supports emulating many types of machines. This includes machines that
> may
> +serve as the main processor in an IPMI system, e.g. x86 or POWER server
> +processors, as well as machines emulating ARM-based Baseband Management
> +Controllers (BMCs), e.g. AST2xxx or NPCM7xxx systems-on-chip.
> +
> +Main processor emulation
> +========================
> +
> +A server platform may include one of the following system interfaces for
> +communicating with a BMC:
> +
> +* A Keyboard Controller Style (KCS) Interface, accessible via ISA
> + (``isa-ipmi-kcs``) or PCI (``pci-ipmi-kcs``).
> +* A Block Transfer (BT) Interface, accessible via ISA (``isa-ipmi-bt``) or
> PCI
> + (``pci-ipmi-bt``).
> +* An SMBus System Interface (SSIF; ``smbus-ipmi``).
> +
> +These interfaces can all be emulated by QEMU. To emulate the behavior of the
> +BMC, the messaging interface emulators use one of the following backends:
> +
> +* A BMC simulator running within the QEMU process (``ipmi-bmc-sim``).
> +* An external BMC simulator or emulator, connected over a chardev
> + (``ipmi-bmc-extern``). `ipmi_sim
> +
> <https://github.com/wrouesnel/openipmi/blob/master/lanserv/README.ipmi_sim>`_
Here, and in the other reference below, can you reference the official
repository instead of your own?
> + from OpenIPMI is an example external BMC emulator.
> +
> +The following diagram shows how these entities relate to each other.
> +
> +.. blockdiag::
> +
> + blockdiag main_processor_ipmi {
> + orientation = portrait
> + default_group_color = "none";
> + class msgif [color = lightblue];
> + class bmc [color = salmon];
> +
> + ipmi_sim [color="aquamarine", label="External BMC"]
> + ipmi-bmc-extern <-> ipmi_sim [label="chardev"];
> +
> + group {
> + orientation = portrait
> +
> + ipmi-interface <-> ipmi-bmc;
> +
> + group {
> + orientation = portrait
> +
> + ipmi-interface [class = "msgif"];
> + isa-ipmi-kcs [class="msgif", stacked];
> +
> + ipmi-interface <- isa-ipmi-kcs [hstyle = generalization];
> + }
> +
> +
> + group {
> + orientation = portrait
> +
> + ipmi-bmc [class = "bmc"];
> + ipmi-bmc-sim [class="bmc"];
> + ipmi-bmc-extern [class="bmc"];
> +
> + ipmi-bmc <- ipmi-bmc-sim [hstyle = generalization];
> + ipmi-bmc <- ipmi-bmc-extern [hstyle = generalization];
> + }
> +
> + }
> + }
> +
> +IPMI System Interfaces
> +----------------------
> +
> +The system software running on the main processor may use a *system
> interface*
> +to communicate with the BMC. These are hardware devices attached to an ISA,
> PCI
> +or i2c bus, and in QEMU, they all need to implement ``ipmi-interface``.
> +This allows a BMC implementation to interact with the system interface in a
> +standard way.
> +
> +IPMI BMC
> +--------
> +
> +The system interface devices delegate emulation of BMC behavior to a BMC
> +device, that is a subclass of ``ipmi-bmc``. This type of device is called
> +a BMC because that's what it looks like to the main processor guest software.
> +
> +The BMC behavior may be simulated within the qemu process (``ipmi-bmc-sim``)
> or
> +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.
> +
> +Wire protocol
> +=============
> +
> +The wire protocol used between ``ipmi-bmc-extern`` and the external BMC
> +emulator is defined by `README.vm
> +<https://github.com/wrouesnel/openipmi/blob/master/lanserv/README.vm>`_ from
> +the OpenIPMI project.
> --
> 2.33.0.309.g3052b89438-goog
>
- [PATCH 0/8] Handing IPMI for emulating BMC, Hao Wu, 2021/09/09
- [PATCH 1/8] docs: enable sphinx blockdiag extension, Hao Wu, 2021/09/09
- [PATCH 2/8] docs/specs: IPMI device emulation: main processor, Hao Wu, 2021/09/09
- Re: [PATCH 2/8] docs/specs: IPMI device emulation: main processor,
Corey Minyard <=
- [PATCH 3/8] docs/specs: IPMI device emulation: BMC, Hao Wu, 2021/09/09
- [PATCH 4/8] hw/ipmi: Refactor IPMI interface, Hao Wu, 2021/09/09
- [PATCH 5/8] hw/ipmi: Take out common from ipmi_bmc_extern.c, Hao Wu, 2021/09/09
- [PATCH 6/8] hw/ipmi: Move handle_command to IPMICoreClass, Hao Wu, 2021/09/09
- [PATCH 7/8] hw/ipmi: Add an IPMI external host device, Hao Wu, 2021/09/09
- [PATCH 8/8] hw/ipmi: Add a KCS Module for NPCM7XX, Hao Wu, 2021/09/09