191 lines
8.6 KiB
Markdown
191 lines
8.6 KiB
Markdown
# Multi-host IPMI design
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Author: Velumani T(velu), [velumanit@hcl](mailto:velumanit@hcl.com) Kumar
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T(kumar_t), [thangavel.k@hcl.com](mailto:thangavel.k@hcl.com)
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Other contributors:
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Created: June 26, 2020
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## Problem Description
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The current version of OpenBMC does not support multi-host implementation in
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IPMI commands handling. We have a multi-host system and proposing the design to
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support multi-host.
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As detailed below the hosts are connected in the IPMB interface, all host
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related communication is based on IPMB. The OpenBMC uses ipmbbridged to manage
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IPMB buses and the IPMB messages are routed to ipmid.
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Issue 1: ipmbridged does not send the channel number (ie HostId) Issue 2: ipmid
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does not have the information on which IPMB channel the request has come from.
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The ipmid handlers should have the host details to fetch the host specific
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responses.
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## Background and References
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IPMI and IPMB System architecture:
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```
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+------------------------------------+
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| BMC |
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| +-----------+ +------------+ | +--------+
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| | | | | | IPMB1| |
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| | | | |-|------| Host-1 |
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| | | | | | | |
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| | | | | | +--------+
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| | | D-Bus | | | +--------+
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| | ipmid |-------| ipmbbridged| | IPMB2| |
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| | | | |-|------| Host-2 |
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| | | | | | | |
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| | | | | | +--------+
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| | | | | | +--------+
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| | | | | | IPMBn| |
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| | | | |-|------| Host-N |
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| | | | | | | |
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| +-----------+ +------------+ | +--------+
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+------------------------------------+
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```
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Hosts are connected with IPMB interface, the hosts can be 1 to N. The IPMB
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request coming from the hosts are routed to ipmid by the ipmbbridged. The IPMB
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requests are routed from ipmid or any service by D-Bus interface and The
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outgoing IPMB requests are routed by ipmbbridged to IPMB interface.
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## Requirements
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The current version of OpenBMC does not support multi-host implementation in
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IPMI commands handling. We have a multi-host system and proposing the design to
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support multi-host.
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## Proposed Design
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To address issue1 and issue2, we propose the following design changes in
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ipmbbridged and ipmid. To address out-of-band IPMI command from the network,the
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proposal is captured in section "Changes in netipmid".
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## Issue1: Changes in ipmbbridged:
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ipmbbridged to send the channel details from where the request is received.
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**Change: Sending Host detail as additional parameter**
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While routing the IPMB requests coming from the host channel, We will be adding
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new entry in the json config file for the host ID '"devIndex": 0' ipmbbridged
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will send '"devIndex": 0' as optional parameter(options) in D-Bus interface to
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ipmid.This can be used to get the information on which IPMB bus the message
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comes from.
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The json file looks like below. Each devIndex can have one "me" and "ipmb"
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channel.To ensure existing platforms does not get affected, if the "devIndex"
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key is not present in the file ipmbbridged uses default "devIndex" as 0.
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{ "type": "me", "slave-path": "/dev/ipmb-1", "bmc-addr": 32, "remote-addr": 64,
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"devIndex": 0 }, { "type": "ipmb", "slave-path": "/dev/ipmb-2", "bmc-addr": 32,
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"remote-addr": 64, "devIndex": 0 }, { "type": "me", "slave-path": "/dev/ipmb-3",
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"bmc-addr": 32, "remote-addr": 64, "devIndex": 1 }, { "type": "ipmb",
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"slave-path": "/dev/ipmb-4", "bmc-addr": 32, "remote-addr": 64, "devIndex": 1 },
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## Issue2: Changes in ipmid:
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Receive the optional parameter sent by the ipmbbridged as host details, while
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receiving the parameter in the executionEntry method call the same will be
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passed to the command handlers in both common and oem handlers.The command
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handlers can make use of the host information to fetch host specific data.
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For example, host1 send a request to get boot order from BMC, BMC maintains data
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separately for each host. When this command comes to ipmid the commands handler
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gets the host in which the command received. The handler will fetch host1 boot
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order details and respond from the command handler. This is applicable for both
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common and oem handlers.
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## Changes in netipmid:
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The "options" parameter can be used for sending the host information from
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netipmid. The changes proposed for ipmbbridged can be used in netipmid as well.
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The netipmid sends the "devIndex" on which channel the request comes from. There
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will not be any further changes required in ipmid. The netipmid can have
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multiple approaches to handle multi-host.Some of the approaches are listed down
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and but not limited to this list.
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1. Virtual Ethernet interfaces - One virtual interface per host.
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2. Different port numbers - Can have different port numbers for each host.
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3. VLAN Ids- VLAN IDs can be used to support multi host. The netipmid shall have
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a config file where in the interfaces can be configured for each host. Also
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one or more interfaces can be configured to each of the host. The interfaces
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can be virtual or physical. Below is the sample configuration file
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{"Host":1, "Interface-1":"eth0", "Interface-2":"eth1", "Interface-3":"veth4",
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"Interface-4":"veth5" }, {"Host":2, "Interface-1":"eth2", "Interface-2":"eth3",
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"Interface-3":"veth1", "Interface-4":"veth2" },
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Example implementation of approach1:Virtual ethernet interface.
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```
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+--------------------------------------------+
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| BMC |
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| +--------+ +-----------+ +------+ | +--------+
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| | | D-Bus | | | | | | |
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| | |-------| netipmid1 |---|veth1 |---------| Host-1 |
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| | | | | | | | | |
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| | | +-----------+ +------+ | +--------+
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| | | +-----------+ +------+ | +--------+
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| | ipmid | D-Bus | | | | | | |
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| | |-------| netipmid2 |---|veth2 |---------| Host-2 |
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| | | | | | | | | |
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| | | +-----------+ +------+ | +--------+
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| | | +-----------+ +------+ | +--------+
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| | | D-Bus | | | | | | |
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| | |-------| netipmidN |---|vethN |---------| Host-N |
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| +--------+ +-----------+ +------+ | +--------+
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+--------------------------------------------+
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```
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In the above diagram one instance of netipmid runs per host. Each instance is
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tied to one virtual ethernet interface, The virtual interface ID can be used to
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make a devIndex. This represents the HostId.
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## Alternatives Considered
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## Approach1:ipmbbridged to send host-id in the payload
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The ipmbbridged shall be modified to send the host id in data payload. This
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looks to be a simple change but impacts the existing platforms which are already
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using it.This may not be a right approach.
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## Approach2:Create multiple ipmid to handle multihost.One ipmid process per host.
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This is a multi service appoach,one instance of ipmid service shall be spawned
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to respond each host.The changes looks simple and no major design change from
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the existing design. But many common handlers will be running as duplicate in
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multiple instances.
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## Approach3:Using a different IPMI channel for handling multiple host.
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Using a different IPMI channel for handling multiple hosts, in the ipmbbridged
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the channel id can be used to identify host. In this approach we will be having
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multiple instances of ipmbbridged and each instance will be registered with the
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a channel number.Maximum channel numbers are limited to 8 as per the
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specification.This limits the maximum hosts to be supported.
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## Impacts
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There may not be an impact in ipmid command handler functions.This design will
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not affect the current functionality.
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## Testing
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The proposed design can be tested in a platform in which the multiple hosts are
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connected.The commands requests are received from all the hosts and responses
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are host specific data.When the request coming from the host as IPMB command,
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ipmbbridged appends devIndex and ipmid receives the respective devIndex.ipmid
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responds based on the received devIndex(Host Id) and response reaches all the
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way to host.The data can be validated in host.
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