Re: [PATCH RFC v7 8/8] admin command list discovery

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

On Thu, Aug 18, 2022 at 04:51:39PM +0800, Jason Wang wrote:
> On Sat, Aug 13, 2022 at 1:19 AM Michael S. Tsirkin <mst@redhat.com> wrote:
> >
> > From: Max Gurtovoy <mgurtovoy@nvidia.com>
> >
> > Add commands to find out which commands does each group support.
> > This will be useful once we have multiple group types.
> 
> I still wonder if it's better to just use different types of
> virtqueues, it seems more simple than this.
> 
> Thanks

I am not sure these commands are needed. Maybe make do with feature bits
for now. But VQs won't solve anything that feature bits won't.

> >
> > Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > ---
> >  admin.tex | 72 +++++++++++++++++++++++++++++++++++++++++++++++++++++--
> >  1 file changed, 70 insertions(+), 2 deletions(-)
> >
> > diff --git a/admin.tex b/admin.tex
> > index 99b6c2a..5956c48 100644
> > --- a/admin.tex
> > +++ b/admin.tex
> > @@ -96,9 +96,11 @@ \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_ACCEPT & Provides to device list of commands used for this group type \\
> > +0002h - 7FFFh & - &  Group administration commands    \\
> >  \hline
> >  8000h - FFFFh   & Reserved    \\
> >  \hline
> > @@ -142,6 +144,72 @@ \subsection{Group administration commands}\label{sec:Basic Facilities of a Virti
> >  structures to the shorter of the two (submitted by driver and
> >  described in this specification).
> >
> > +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_ACCEPT.
> > +
> > +
> > +Commands VIRTIO_ADMIN_CMD_LIST_QUERY and VIRTIO_ADMIN_CMD_LIST_ACCEPT
> > +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. For example, the array of size 2 including
> > +the values 0x3 and 0x1 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_ACCEPT) must
> > +always be set in \field{device_admin_cmds}.
> > +
> > +
> > +For the command VIRTIO_ADMIN_CMD_LIST_QUERY, \field{opcode} is set to 0x0.
> > +The \field{group_member_id} is unused. It must be set to zero by driver.
> > +This command has no command specific data.
> > +The device, upon success, returns a 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_ACCEPT, \field{opcode}
> > +is set to 0x1.
> > +The \field{group_member_id} is unused. It must be set to zero by driver.
> > +The 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.  before sending
> > +any commands for any member of a group.
> > +
> > +The driver then accepts some of the opcodes by sending to
> > +the device the command VIRTIO_ADMIN_CMD_LIST_ACCEPT 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 SHOULD NOT set bits in device_admin_cmds
> > +if they are not familiar with how the command opcode
> > +is used, since devices MAY 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 Virtqueue}\label{sec:Basic Facilities of a Virtio Device / Group Administration Virtqueues}
> >
> >  An administration virtqueue of a parent device is used to submit
> > --
> > MST
> >