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Subject: Re: [PATCH v8 8/9] admin: command list discovery
On Tue, Nov 22 2022, "Michael S. Tsirkin" <mst@redhat.com> wrote: > On Tue, Nov 22, 2022 at 04:25:23PM +0100, Cornelia Huck wrote: >> On Sun, Nov 20 2022, "Michael S. Tsirkin" <mst@redhat.com> wrote: > Using 0x instead of h suffix? Sure. > > We should probably document the syntax in introduction.tex > though this seems low priority. Nod. >> > +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 \\ >> >> Either 0x00, or decimal (which one is better?) > > I think I prefer 0x here. And maybe I will add status values in both hex > and decimal (I used decimal to be consistent with linux headers but > fundamentally what we use most of the time is hex). Ok. > >> > +\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 \\ >> >> s/was set// >> >> > +\hline >> > +04h & VIRTIO_ADMIN_STATUS_Q_INVALID_MEM & unsupported or invalid \field{group_member_id} was set \\ >> >> s/was set// >> >> > +\hline >> > +other & - & group administration command error \\ >> >> Again the question whether this is something that can be defined per >> group type. > > probably - above ones are generic, let's see if we need specific ones. > if yes will be easy to add. I think we want to distinguish between "reserved" (not defined yet, may get a meaning later on) and "group type specific" (a group type may use it, don't reuse for generic stuff). If we need group type specific errors (and don't want a free-for-all), we could go with eg. 0x05 & VIRTIO_ADMIN_STATUS_Q_GROUP_ERR_0 & group type specific error \\ or so? Do we see any need for that yet? >> > +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. >> >> Can the driver later change its mind, i.e. use VIRTIO_ADMIN_CMD_LIST_USE >> a second time with a different set of commands? If yes, can it add >> commands, or only withdraw them? > > I think it's ok to allow changing them arbitrarily at any time. > If driver wants to "lock down" the list then all it has to do > is send a list with VIRTIO_ADMIN_CMD_LIST_USE cleared. > > It seemed clear along the lines of since it's not prohibited it's > allowed but since the question arose I will add a conformance clause for > this. So if the driver sends LIST_USE with an additional command, and the device rejects that list (because of dependencies or whatever), is the list of commands supposed to stay whatever it was prior to that? > > >> What happens if a driver tries to send a command that it had not >> included in the list? > > > This is covered in conformance statements in the next patch. > > + > +Device MUST validate commands against the list used by > +driver and MUST fail any commands not in the list with > +\field{status} set to VIRTIO_ADMIN_STATUS_EINVAL > +and \field{status_qualifier} set to > +VIRTIO_ADMIN_STATUS_Q_INVALID_OPCODE. Ok.
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