docs/designs/bmc-reset-with-host-up.md

1 # BMC Reset with Host Booted
18 A good portion of this is explained in the phosphor-state-manager [README][1].
20 This design doc is written to formalize the design and add some more details on
25 it then checks the host to see if it is up and alive. If the power is on and the
28 - /run/openbmc/chassis@0-on
29 - /run/openbmc/host@0-on
31 It should be noted that although full support is not in place for multi-chassis
32 and multi-host systems, the framework is there to build on.
33 `op-reset-chassis-running@.service` is a templated service, checking pgood in
34 its instances power domain. It creates a file in the filesystem,
35 /run/openbmc/chassis@%i-on, to indicate power is on for that instance. Similar
36 implementation is done for the host via `phosphor-reset-host-check@.service` and
37 the file /run/openbmc/host@%i-on.
39 If chassis power is on and the host is up, then `obmc-chassis-poweron@.target`
40 and `obmc-host-start@.target` are started.
44 is already powered on and the host is running, there is no need to actually turn
45 power on, or start the host. The behavior wanted is that these services "start"
49 - `ConditionPathExists=!/run/openbmc/chassis@%i-on`
50 - `ConditionPathExists=!/run/openbmc/host@%i-on`
55 Different systems have different requirements on what the behavior should be
56 when the chassis power is on, but the host is unreachable. This design needs to
60 systems have a hybrid approach where depending on where the host was in its
65 - Support both IPMI and PLDM as mechanisms to determine if the host is running.
66   - Allow either or both to be enabled
67 - Support custom behavior when chassis power is on but the BMC is unable to
69 - Both IPMI and PLDM stacks will give the host a set amount of time to respond.
72   - This time limit must be configurable at build time
73 - IPMI and PLDM will implement a phosphor-dbus-interface interface,
80 - IPMI will continue to utilize the SMS_ATN command to indicate to the host that
86 - PLDM will utilize a GetTID command to the host to determine if it is running
87 - Where applicable, PLDM will provide a mechanism to distinguish between
89   - For example, on IBM systems there is a difference between the hostboot (host
91     firmware and talking PLDM but the BMC recovery paths will differ based on
99 - Check pgood
100 - Call mapper for all implementations of
102 - Read `CurrentFirmwareCondition` property of all interface. If any call returns
104 - Otherwise, check host via any custom mechanisms
105 - Execute automated recovery of host if desired
108 services and applications within phosphor-state-manager will coordinate the
110 discover if the host is running. Based on the response from these queries the
111 software in phosphor-state-manager will take the appropriate action of creating
116 within phosphor-state-manager. Any system or company specific services can be
119 - `obmc-chassis-powerreset@.target.require`
120 - `obmc-host-reset@.target.requires`
124 A separate service and application will be created within phosphor-state-manager
125 to execute the following logic in situations where chassis power is on but the
129 - If chassis power on (/run/openbmc/chassis@%i-on)
130 - And host is off (!ConditionPathExists=!/run/openbmc/host@%i-on)
131 - And restored BootProgress is not None
132 - Then (assume host was booting before BMC reboot)
133   - Log error indicating situation
134   - Move host to Quiesce and allow automated recovery to kick in
136 ### Note on custom mechanism for IBM systems
141 If the chassis power is on but the BMC is unable to communicate with the host
147 the host as-is, even if it is unable to communicate with the host over IPMI or
158 also be cleared by the BMC firmware on power off's, system checkstops, and
168 own custom host-detection applications in.
178 the host continued to run without issue throughout the BMC reset.
182 - Reboot the BMC while the host is booting, but before it's in a state where it
186 - Reboot the BMC when the host is up and running but disable the IPMI/PLDM stack
187   on the host so it does not respond to the BMC when it comes back from its
192   https://github.com/openbmc/phosphor-state-manager#bmc-reset-with-host-andor-chassis-on