virtio — archive

[Michael S. Tsirkin <mst@redhat.com>]

On Thu, Mar 02, 2023 at 03:10:11PM -0500, Stefan Hajnoczi wrote: > On Thu, Mar 02, 2023 at 08:05:02AM -0500, Michael S. Tsirkin wrote: > > This introduces a general structure for group administration commands, > > used to control device groups through their owner. > > > > Following patches will introduce specific commands and an interface for > > submitting these commands to the owner. > > > > Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com> > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > > --- > > admin.tex | 108 +++++++++++++++++++++++++++++++++++++++++++++++ > > introduction.tex | 3 ++ > > 2 files changed, 111 insertions(+) > > > > diff --git a/admin.tex b/admin.tex > > index 3dc47be..7e28b77 100644 > > --- a/admin.tex > > +++ b/admin.tex > > @@ -46,4 +46,112 @@ \section{Device groups}\label{sec:Basic Facilities of a Virtio Device / Device g > > PCI transport (see \ref{sec:Virtio Transport Options / Virtio Over PCI Bus}). > > \end{description} > > > > +\subsection{Group administration commands}\label{sec:Basic Facilities of a Virtio Device / Device groups / Group administration commands} > > > > +The driver sends group administration commands to the owner device of > > I notice that the terminology is simply "the driver". "Owner driver" > and "group member driver" might be clearer because there will be two > (possibly different) drivers involved. Hmm I don't really want to repeat owner everywhere. I will clarify that in this section simple "driver" and "device" are owner, "member device" and "member driver" is always called explicitly. > > +a group to control member devices of the group. > > +This mechanism can > > +be used, for example, to configure a member device before it is > > +initialized by its driver. > > +\footnote{The term "administration" is intended to be interpreted > > +widely to include any kind of control. See specific commands > > +for detail.} > > + > > +All the group administration commands are of the following form: > > + > > +\begin{lstlisting} > > +struct virtio_admin_cmd { > > + /* Device-readable part */ > > + le16 opcode; > > + /* > > + * 1 - SR-IOV > > + * 2 - 65535 reserved > > + */ > > + le16 group_type; > > + /* unused, reserved for future extensions */ > > + u8 reserved1[12]; > > + le64 group_member_id; > > + u8 command_specific_data[]; > > + > > + /* Device-writable part */ > > + le16 status; > > + le16 status_qualifier; > > + /* unused, reserved for future extensions */ > > + u8 reserved2[4]; > > + u8 command_specific_result[]; > > +}; > > +\end{lstlisting} > > + > > +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 > > +\field{command_specific_result}. > > + > > +Generally, any unused device-readable fields are set to zero by the driver > > +and ignored by the device. Any unused device-writeable fields are set to zero > > +by the device and ignored by the driver. > > + > > +\field{opcode} specifies the command. The valid > > +values for \field{opcode} can be found in the following table: > > + > > +\begin{tabular}{|l|l|} > > +\hline > > +opcode & Name & Command Description \\ > > +\hline \hline > > +0x0000 - 0x7FFF & - & Group administration commands \\ > > +\hline > > +0x8000 - 0xFFFF & - & Reserved \\ > > +\hline > > +\end{tabular} > > I thought all commands are "group administration commands" but this > table makes it look like they are just a subset (0x0000 - 0x7FFF) of > group administration commands, which is a paradox. Well the rest are reserved, maybe we will have more command types who knows. No? > > + > > +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 type identifier and group member > > +identifier. > > + > > +The following table describes possible \field{status} values; > > +to simplify common implementations, they are intentionally > > +matching common \hyperref[intro:errno]{Linux error names and numbers}: > > + > > +\begin{tabular}{|l|l|l|} > > +\hline > > +Status (decimal) & Name & Description \\ > > +\hline \hline > > +00 & VIRTIO_ADMIN_STATUS_OK & successful completion \\ > > +\hline > > +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} > > s/qialifier/qualifier/ > > > +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: > > s/qialifier/qualifier/ > > > +\begin{tabular}{|l|l|l|} > > +\hline > > +Status & Name & Description \\ > > +\hline \hline > > +0x00 & VIRTIO_ADMIN_STATUS_Q_INVALID_COMMAND & command error: no additional information \\ > > +\hline > > +0x01 & VIRTIO_ADMIN_STATUS_Q_INVALID_OPCODE & unsupported or invalid \field{opcode} \\ > > +\hline > > +0x02 & VIRTIO_ADMIN_STATUS_Q_INVALID_FIELD & unsupported or invalid field within \field{command_specific_data} \\ > > +\hline > > +0x03 & VIRTIO_ADMIN_STATUS_Q_INVALID_GROUP & unsupported or invalid \field{group_type} \\ > > +\hline > > +0x04 & VIRTIO_ADMIN_STATUS_Q_INVALID_MEMBER & unsupported or invalid \field{group_member_id} \\ > > +\hline > > +0x05-0xFFFF & - & reserved for future use \\ > > +\hline > > +\end{tabular} > > + > > +Each command uses a different \field{command_specific_data} and > > +\field{command_specific_result} structures and the length of > > +\field{command_specific_data} and \field{command_specific_result} > > +depends on these structures and is described separately or is > > +implicit in the structure description. > > On more thing: > > Does the owner device see commands in order but may complete them in any > order? > > I think this information might be useful just to make it clear that > driver authors shouldn't make assumptions about ordering and completion > order, e.g. pipelining a bunch of dependent commands doesn't work > because the first command is not necessarily completed before the second > command is started. I think this is discussed when we discuss sending commands through vq. in this section it's just about commands generally whatever the way to send them to device. no?