RE: [PATCH v8 8/9] admin: command list discovery

["Uminski, Piotr" <Piotr.Uminski@intel.com>]

Instead of a bit-coded list of supported commands, can we just use an array of supported command values? It allows us to use non-contiguous command coding and checking how big  is an array:       le32 device_admin_cmds[];


-----Original Message-----
From: Michael S. Tsirkin <mst@redhat.com> 
Sent: Monday, November 21, 2022 2:26 AM
To: virtio-comment@lists.oasis-open.org; virtio-dev@lists.oasis-open.org; jasowang@redhat.com; mst@redhat.com; cohuck@redhat.com; sgarzare@redhat.com; stefanha@redhat.com; Jani, Nrupal <nrupal.jani@intel.com>; Uminski, Piotr <Piotr.Uminski@intel.com>; Yuan, Hang <hang.yuan@intel.com>
Cc: virtio@lists.oasis-open.org; Zhu, Lingshan <lingshan.zhu@intel.com>; pasic@linux.ibm.com; Shahaf Shuler <shahafs@nvidia.com>; Parav Pandit <parav@nvidia.com>; Max Gurtovoy <mgurtovoy@nvidia.com>
Subject: [PATCH v8 8/9] admin: command list discovery

Add commands to find out which commands does each group support, as well as enable their use by driver.
This will be especially useful once we have multiple group types.

Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 admin.tex | 130 +++++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 114 insertions(+), 16 deletions(-)

diff --git a/admin.tex b/admin.tex
index bfa63a2..589e06a 100644
--- a/admin.tex
+++ b/admin.tex
@@ -72,13 +72,14 @@ \subsection{Group administration commands}\label{sec:Basic Facilities of a Virti
 
         /* Device-writable part */
         le16 status;
+        le16 status_qualifier;
         /* unused, reserved for future extensions */
-        u8 reserved2[6];
+        u8 reserved2[4];
         u8 command_specific_result[];
 };
 \end{lstlisting}
 
-For all commands, \field{opcode}, \field{group_id} and if
+For all commands, \field{opcode}, \field{group_type} and if
 necessary \field{group_member_id} and \field{command_specific_data} are  set by the driver, and the owner device sets \field{status} and if  needed \field{status_qualifier} and @@ -93,18 +94,20 @@ \subsection{Group administration commands}\label{sec:Basic Facilities of a Virti
 
 \begin{tabular}{|l|l|}
 \hline
-opcode & Command Description \\
+opcode & Name & Command Description \\
 \hline \hline
-0000h - 7FFFh   & Group administration commands    \\
+0000h & VIRTIO_ADMIN_CMD_LIST_QUERY & Provides to driver list of commands supported for this group type    \\
+0001h & VIRTIO_ADMIN_CMD_LIST_USE & Provides to device list of commands used for this group type \\
+0002h - 7FFFh & - &  Group administration commands    \\
 \hline
 8000h - FFFFh   & Reserved    \\
 \hline
 \end{tabular}
 
-The \field{group_id} specifies the device group.
-The \field{group_member_id} specifies the member device within the group.
+The \field{group_type} specifies the group type identifier.
+The \field{group_member_id} specifies the member identifier within the group.
 See section \ref{sec:Introduction / Terminology / Device group} -for the definition of the group identifier and group member
+for the definition of the group type identifier and group member
 identifier.
 
 The following table describes possible \field{status} values, @@ -113,22 +116,117 @@ \subsection{Group administration commands}\label{sec:Basic Facilities of a Virti
 
 \begin{tabular}{|l|l|l|}
 \hline
-Status & Name & Description \\
+Status (decimal) & Name & Description \\
 \hline \hline
-00h   & VIRTIO_ADMIN_STATUS_OK    & successful completion  \\
+00   & VIRTIO_ADMIN_STATUS_OK    & successful completion  \\
 \hline
-01h   & VIRTIO_ADMIN_STATUS_INVALID_OPCODE    & unsupported or invalid \field{opcode}  \\
-\hline
-02h   & VIRTIO_ADMIN_STATUS_INVALID_FIELD    & invalid field within command specific data  \\
-\hline
-03h   & VIRTIO_ADMIN_STATUS_INVALID_GROUP    & invalid group identifier was set  \\
-\hline
-04h   & VIRTIO_ADMIN_STATUS_INVALID_MEM    & invalid group member identifier was set  \\
+22   & VIRTIO_ADMIN_STATUS_EINVAL    & invalid command \\
 \hline
 other   & -    & group administration command error  \\
 \hline
 \end{tabular}
 
+When \field{status} is VIRTIO_ADMIN_STATUS_OK, \field{status_qialifier} 
+is reserved and set to zero by the device.
+
+When \field{status} is VIRTIO_ADMIN_STATUS_EINVAL, the following table 
+describes possible \field{status_qialifier} values:
+\begin{tabular}{|l|l|l|}
+\hline
+Status & Name & Description \\
+\hline \hline
+00h   & VIRTIO_ADMIN_STATUS_Q_INVALID_COMMAND   & command error: no additional information  \\
+\hline
+01h   & VIRTIO_ADMIN_STATUS_Q_INVALID_OPCODE    & unsupported or invalid \field{opcode}  \\
+\hline
+02h   & VIRTIO_ADMIN_STATUS_Q_INVALID_FIELD    & unsupported or invalid field within \field{command_specific_data}  \\
+\hline
+03h   & VIRTIO_ADMIN_STATUS_Q_INVALID_GROUP    & unsupported or invalid \field{group_type} was set  \\
+\hline
+04h   & VIRTIO_ADMIN_STATUS_Q_INVALID_MEM    & unsupported or invalid \field{group_member_id} was set  \\
+\hline
+other   & -    & group administration command error  \\
+\hline
+\end{tabular}
+
+Before sending any administration commands to the device, the commands 
+in question are reported to the device as used by the driver.
+Initially (after reset), only two commands are assumed to be used:
+VIRTIO_ADMIN_CMD_LIST_QUERY and VIRTIO_ADMIN_CMD_LIST_USE.
+
+Accordingly,
+before sending any other commands for any member of a specific group to 
+the device, the driver issues the commands VIRTIO_ADMIN_CMD_LIST_QUERY 
+and VIRTIO_ADMIN_CMD_LIST_USE.
+
+Commands VIRTIO_ADMIN_CMD_LIST_QUERY and VIRTIO_ADMIN_CMD_LIST_USE both 
+use the following structure describing the command opcodes:
+
+\begin{lstlisting}
+struct virtio_admin_cmd_list {
+       /* Indicates which of the below fields were returned
+       le32 device_admin_cmds[];
+};
+\end{lstlisting}
+
+This structure is an array of 32 bit values in little-endian byte 
+order, in which a bit is set if the specific command opcode is 
+supported. Thus, \field{device_admin_cmds[0]} refers to the first 
+32-bit value in this array corresponding to opcodes 0 to 31, 
+\field{device_admin_cmds[1]} is the second 32-bit value corresponding 
+to opcodes 32 to 63, etc.
+For example, the array of size 2 including the values 0x3 in 
+\field{device_admin_cmds[0]} and 0x1 in \field{device_admin_cmds[1]} 
+indicates that only opcodes 0, 1 and 32 are supported.
+
+Accordingly, bits 0 and 1 corresponding to opcode 0
+(VIRTIO_ADMIN_CMD_LIST_QUERY) and 1
+(VIRTIO_ADMIN_CMD_LIST_USE) are
+always set in \field{device_admin_cmds[0]} returned by VIRTIO_ADMIN_CMD_LIST_QUERY.
+
+For the command VIRTIO_ADMIN_CMD_LIST_QUERY, \field{opcode} is set to 0x0.
+The \field{group_member_id} is unused. It is set to zero by driver.
+This command has no command specific data.
+The device, upon success, returns a result in 
+\field{command_specific_result} in the format \field{struct 
+virtio_admin_cmd_list} describing the list of administration commands 
+supported for the given group.
+
+
+For the command VIRTIO_ADMIN_CMD_LIST_USE, \field{opcode} is set to 
+0x1.
+The \field{group_member_id} is unused. It is set to zero by driver.
+The \field{command_specific_data} is in the format \field{struct 
+virtio_admin_cmd_list} describing the list of administration commands 
+used by the driver.
+This command has no command specific result.
+
+The driver issues the command VIRTIO_ADMIN_CMD_LIST_QUERY to query the 
+list of commands valid for this group and before sending any commands 
+for any member of a group.
+
+The driver then enables use of some of the opcodes by sending to the 
+device the command VIRTIO_ADMIN_CMD_LIST_USE with a subset of the list 
+returned by VIRTIO_ADMIN_CMD_LIST_QUERY that is both understood and 
+used by the driver.
+
+If the device supports the command list used by the driver, the device 
+completes the command with status VIRTIO_ADMIN_STATUS_OK.
+If the device does not support the command list, the device completes 
+the command with status VIRTIO_ADMIN_STATUS_INVALID_FIELD.
+
+Note: drivers are assumed not to set bits in device_admin_cmds if they 
+are not familiar with how the command opcode is used, since devices 
+could have dependencies between command opcodes.
+
+It is assumed that all members in a group support and are used with the 
+same list of commands.
+
 \section{Administration Virtqueues}\label{sec:Basic Facilities of a Virtio Device / Administration Virtqueues}
 
 An administration virtqueue of an owner device is used to submit
--
MST

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