virtio — archive

[Parav Pandit <parav@nvidia.com>]

On 4/3/2023 11:03 AM, 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. > > Note that the commands are focused on controlling device groups: > this is why group related fields are in the generic part of > the structure. > Without this the admin vq would become a "whatever" vq which does not do The abbreviation vq for virtqueue looks good here :) > anything specific at all, just a general transport like thing. > I feel going this way opens the design space to the point where > we no longer know what belongs in e.g. config space > what in the control q and what in the admin q. Better to refer them as control vq and admin vq like above. > As it is, whatever deals with groups is in the admin q; other admin vq. > things not in the admin q. admin vq. > > There are specific exceptions such as query but that's an exception that > proves the rule ;) > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > --- > > changes since v10: > explain the role of status vs status_qualifier, addresses > multiple comments > add more status values and appropriate qualifiers, > as suggested by Parav > clarify reserved command opcodes as suggested by Stefan > better formatting for ranges, comment by Jiri > make sure command-specific-data is a multiple of qword, > so things are aligned, suggested by Jiri > add Q_OK qualifier for success > --- > admin.tex | 121 +++++++++++++++++++++++++++++++++++++++++++++++ > introduction.tex | 3 ++ > 2 files changed, 124 insertions(+) > > diff --git a/admin.tex b/admin.tex > index 04d5498..c869a1a 100644 > --- a/admin.tex > +++ b/admin.tex > @@ -60,4 +60,125 @@ \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 > +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; > + le64 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 & - & Commands using \field{struct virtio_admin_cmd} \\ > +\hline > +0x8000 - 0xFFFF & - & Reserved for future commands (possibly using a different structure) \\ > +\hline > +\end{tabular} > + > +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 \field{status} describes the command result and possibly > +failure reason at an abstract level, this is appropriate for > +forwarding to applications. The \field{status_qualifier} describes > +failures at a low virtio specific level, as appropriate for debugging. > +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 > +11 & VIRTIO_ADMIN_STATUS_EAGAIN & try again \\ > +\hline > +12 & VIRTIO_ADMIN_STATUS_ENOMEM & insufficient resources \\ > +\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_qualifier} > +is reserved and set to zero by the device. > + > +The following table describes possible \field{status_qualifier} values: > +\begin{tabular}{|l|l|l|} > +\hline > +Status & Name & Description \\ > +\hline \hline > +0x00 & VIRTIO_ADMIN_STATUS_Q_OK & used with VIRTIO_ADMIN_STATUS_OK \\ > +\hline > +0x01 & VIRTIO_ADMIN_STATUS_Q_INVALID_COMMAND & command error: no additional information \\ > +\hline > +0x02 & VIRTIO_ADMIN_STATUS_Q_INVALID_OPCODE & unsupported or invalid \field{opcode} \\ > +\hline > +0x03 & VIRTIO_ADMIN_STATUS_Q_INVALID_FIELD & unsupported or invalid field within \field{command_specific_data} \\ > +\hline > +0x04 & VIRTIO_ADMIN_STATUS_Q_INVALID_GROUP & unsupported or invalid \field{group_type} \\ > +\hline > +0x05 & VIRTIO_ADMIN_STATUS_Q_INVALID_MEMBER & unsupported or invalid \field{group_member_id} \\ > +\hline > +0x06 & VIRTIO_ADMIN_STATUS_Q_NORESOURCE & out of internal resources: ok to retry \\ > +\hline > +0x07 & VIRTIO_ADMIN_STATUS_Q_TRYAGAIN & command blocks for too long: should retry \\ > +\hline > +0x08-0xFFFF & - & 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. > diff --git a/introduction.tex b/introduction.tex > index 287c5fc..0d849a9 100644 > --- a/introduction.tex > +++ b/introduction.tex > @@ -68,6 +68,9 @@ \section{Normative References}\label{sec:Normative References} > \phantomsection\label{intro:FUSE}\textbf{[FUSE]} & > Linux FUSE interface, > \newline\url{https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/uapi/linux/fuse.h}\\ > + \phantomsection\label{intro:errno}\textbf{[errno]} & > + Linux error names and numbers, > + \newline\url{https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/uapi/uapi/asm-generic/errno-base.h}\\ Above link is broken because "uapi" is twice. Please remove one "uapi/". > \phantomsection\label{intro:eMMC}\textbf{[eMMC]} & > eMMC Electrical Standard (5.1), JESD84-B51, > \newline\url{http://www.jedec.org/sites/default/files/docs/JESD84-B51.pdf}\\ With above url link fix, Reviewed-by: Parav Pandit <parav@nvidia.com>