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Define request forward service group #63

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Oct 14, 2024
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Define request forward service group #63

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2 changes: 2 additions & 0 deletions riscv-rpmi.adoc
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Expand Up @@ -94,6 +94,8 @@ include::src/srvgrp-management.adoc[]

include::src/srvgrp-ras-agent.adoc[]

include::src/srvgrp-request-forward.adoc[]

include::src/rpmi-mpxy.adoc[]

// The index must precede the bibliography
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6 changes: 5 additions & 1 deletion src/message-protocol.adoc
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Expand Up @@ -340,8 +340,12 @@ specification or the extension version mismatch.
| -13
| Input/Output error.

| RPMI_ERR_NO_DATA
| -14
| Data not available.

|
| -14 to -127
| -15 to -127
| _Reserved_

|
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7 changes: 6 additions & 1 deletion src/service-groups.adoc
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Expand Up @@ -110,7 +110,12 @@ defined by this specification.
| RAS_AGENT
| M-mode, S-mode

| 0x000C - 0x7FFF
| 0x000C
|
| REQUEST_FORWARD
| M-mode, S-mode

| 0x000D - 0x7FFF
|
| _Reserved for Future Use_
|
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252 changes: 252 additions & 0 deletions src/srvgrp-request-forward.adoc
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@@ -0,0 +1,252 @@
:path: src/
:imagesdir: ../images

ifdef::rootpath[]
:imagesdir: {rootpath}{path}{imagesdir}
endif::rootpath[]

ifndef::rootpath[]
:rootpath: ./../
endif::rootpath[]

=== Service Group - REQUEST_FORWARD (SERVICEGROUP_ID: 0x000C)
The REQUEST_FORWARD service group allows application processors to retrieve and
process RPMI request messages which are forwarded by platform microcontroller from
some other RPMI client. This service group also allows an SBI implementation to
forward RPMI request messages from one system-level partition (or domain) to another
using the SBI MPXY extension cite:[SBI].

The platform microcontroller (or SBI implementation) should maintain a first-in
first-out queue of forwarded RPMI request messages. The first (or oldest) forwarded
RPMI request message in the queue is referred to as the current forwarded RPMI request
message. The RPMI services defined by the REQUEST_FORWARD service group allow application
processors to retrieve and process one forwarded RPMI request message at a time.

The <<table_reqfwd_services>> below lists the services defined by the REQUEST_FORWARD
service group:

[#table_reqfwd_services]
.Request Forward Services
[cols="1, 4, 2", width=100%, align="center", options="header"]
|===
| Service ID
| Service Name
| Request Type

| 0x01
| REQFWD_ENABLE_NOTIFICATION
| NORMAL_REQUEST

| 0x02
| REQFWD_RETRIEVE_CURRENT_MESSAGE
| NORMAL_REQUEST

| 0x03
| REQFWD_COMPLETE_CURRENT_MESSAGE
| NORMAL_REQUEST
|===

[#reqfwd-notifications]
==== Notifications
The <<table_reqfwd_notification_events>> below list the notification events
defined by the REQUEST_FORWARD service group.

[#table_reqfwd_notification_events]
.Request Forward Notification Events
[cols="1, 2, 2, 2", width=100%, align="center", options="header"]
|===
| Event ID
| Name
| Event Data
| Description

| 0x01
| REQFWD_NEW_MESSAGE
| An array of `N` bytes representing the first `N` bytes of the current forwarded
RPMI request message. The value `N` is specified by the `EVENT_DATALEN` field of
the RPMI notification event as shown in <<table_notification_message_format>>.
Comment on lines +65 to +67
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Don't we need a word in the event data for either the total or remaining message length, so the caller knows if it needs to call REQFWD_RETRIEVE_CURRENT_MESSAGE at all?

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The event data has the first N bytes of the forwarded RPMI request message so it will include the forwarded RPMI header which can be used to compute the total message length (i.e. datalen in RPMI header + 8).

If event data size is less than 8 bytes then event data is of no use since it has partial RPMI header and we have to use REQFWD_RETRIEVE_CURRENT_MESSAGE service to get the forwarded RPMI request message.

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Ah, that makes sense, since we are limiting the payload to RPMI. Thanks.

| This RPMI notification event represents the arrival of a new forwarded RPMI
request message when there were no other pending forwarded RPMI request message
in the queue.
|===

==== Service: REQFWD_ENABLE_NOTIFICATION (SERVICE_ID: 0x01)
This service allows the application processor to subscribe to REQUEST_FORWARD
service group notifications. The supported events are described in the
<<table_reqfwd_notification_events>>.

[#table_reqfwd_enable_notif_request_data]
.Request Data
[cols="1, 2, 1, 7", width=100%, align="center", options="header"]
|===
| Word
| Name
| Type
| Description

| 0
| EVENT_ID
| uint32
| Event to be subscribed for notification.
|===

[#table_reqfwd_enable_notif_response_data]
.Response Data
[cols="1, 2, 1, 7a", width=100%, align="center", options="header"]
|===
| Word
| Name
| Type
| Description

| 0
| STATUS
| int32
| Return error code

[cols="5,5", options="header"]
!===
! Error Code
! Description

! RPMI_SUCCESS
! Event is subscribed successfully.

! RPMI_ERR_INVALID_PARAM
! `EVENT_ID` is invalid.

! RPMI_ERR_NOT_SUPPORTED
! Notification is not supported.

!===
- Other errors <<table_error_codes>>
|===

==== Service: REQFWD_RETRIEVE_CURRENT_MESSAGE (SERVICE_ID: 0x02)
This service allows application processors to retrieve the current forwarded RPMI
request message. The current message may be the oldest forwarded RPMI request
message in the platform microcontroller (or SBI implementation) queue.

[#table_reqfwd_retireve_current_message_request_data]
.Request Data
[cols="1, 3, 1, 7", width=100%, align="center", options="header"]
|===
| Word
| Name
| Type
| Description

| 0
| START_INDEX
| uint32
| Starting index of first byte of the current forwarded RPMI request message. Use
`0` for the first call, subsequent calls will use the next index of the remaining
bytes.
|===

[#table_reqfwd_retireve_current_message_response_data]
.Response Data
[cols="1, 3, 1, 7a", width=100%, align="center", options="header"]
|===
| Word
| Name
| Type
| Description

| 0
| STATUS
| int32
| Return error code

[cols="7,5", options="header"]
!===
! Error Code
! Description

! RPMI_SUCCESS
! Service completed successfully.

! RPMI_ERR_INVALID_PARAM
! `START_INDEX` is invalid.

! RPMI_ERR_NO_DATA
! No forwarded RPMI request message available.

!===
- Other errors <<table_error_codes>>

| 1
| REMAINING
| uint32
| Remaining number of bytes in the current forwarded RPMI request message.

| 2
| RETURNED
| uint32
| Number of bytes `N` of the current forwarded RPMI request message returned in
this request.

| 3
| REQUEST_MESSAGE[N]
| uint8
| An array of `N` bytes representing a part of the current forwarded RPMI request
message at byte offset specified by `START_INDEX`.
|===

==== Service: REQFWD_COMPLETE_CURRENT_MESSAGE (SERVICE_ID: 0x03)
This service allows the application processors to inform the platform microcontroller
(or SBI implementation) that:

* The processing of the current forwarded RPMI request message has completed and
RPMI response message must be sent to the original source of RPMI request message.
* The current forwarded RPMI request message must now point to the next forwarded
RPMI request message if available.

[#table_reqfwd_complete_current_message_request_data]
.Request Data
[cols="1, 3, 1, 7", width=100%, align="center", options="header"]
|===
| Word
| Name
| Type
| Description

| 0
| RESPONSE_DATA[N]
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Do we need a word for length (N) of RESPONSE_DATA?

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The N can be inferred from DATALEN in RPMI message header.

| uint8
| An array of bytes representing the RPMI message data to be send as
response data for the current forwarded RPMI request message. The `N`
represents the total number of bytes in the response data which can be
inferred by the platform microcontroller (or SBI implementation) from
the overall size of the `REQFWD_COMPLETE_CURRENT_MESSAGE` service message.
|===

[#table_reqfwd_complete_current_message_response_data]
.Response Data
[cols="1, 3, 1, 7a", width=100%, align="center", options="header"]
|===
| Word
| Name
| Type
| Description

| 0
| STATUS
| int32
| Return error code

[cols="7,5", options="header"]
!===
! Error Code
! Description

! RPMI_SUCCESS
! Service completed successfully.

! RPMI_ERR_NO_DATA
! No forwarded RPMI request message available.

!===
- Other errors <<table_error_codes>>

|===
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