virtio — archive

[Parav Pandit <parav@nvidia.com>]

On 4/24/2023 12:44 PM, Michael S. Tsirkin wrote: > 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. > > An alternative is per-type VQs. This is possible but will > require more per-transport work. Discovery through the vq > helps keep things contained. > > e.g. lack of support for some command can switch to a legacy mode > > note that commands are expected to be avolved by adding new You missed to correct the spelling given comment [1] in v11. [1] 74a52ec2-da51-d739-176f-84e4357d9da6@nvidia.com/">https://lore.kernel.org/virtio-dev/74a52ec2-da51-d739-176f-84e4357d9da6@nvidia.com/ > fields to command specific data at the tail, so > we generally do not need feature bits for compatibility. > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> > Reviewed-by: Zhu Lingshan <lingshan.zhu@intel.com> > > --- > > changes in v12: > > devices->device address comment by parav > > changes in v11: > > dropped S.O.B by Max > explain in commit log how commands will evolve, comment by Stefan > replace will use with is capable of use, comment by Stefan > typo fix reported by David and Lingshan > rename cmds to cmd_opcodes suggested by Jiri > list group_type explicitly in command description suggested by Jiri > clarify how can device not support some commands > always say group administration commands, comment by Jiri > --- > admin.tex | 102 +++++++++++++++++++++++++++++++++++++++++++++++++++++- > 1 file changed, 101 insertions(+), 1 deletion(-) > > diff --git a/admin.tex b/admin.tex > index 91e0cba..68ee7e5 100644 > --- a/admin.tex > +++ b/admin.tex > @@ -113,7 +113,9 @@ \subsection{Group administration commands}\label{sec:Basic Facilities of a Virti > \hline > opcode & Name & Command Description \\ > \hline \hline > -0x0000 - 0x7FFF & - & Commands using \field{struct virtio_admin_cmd} \\ > +0x0000 & VIRTIO_ADMIN_CMD_LIST_QUERY & Provides to driver list of commands supported for this group type \\ > +0x0001 & VIRTIO_ADMIN_CMD_LIST_USE & Provides to device list of commands used for this group type \\ > +0x0002 - 0x7FFF & - & Commands using \field{struct virtio_admin_cmd} \\ > \hline > 0x8000 - 0xFFFF & - & Reserved for future commands (possibly using a different structure) \\ > \hline > @@ -183,6 +185,104 @@ \subsection{Group administration commands}\label{sec:Basic Facilities of a Virti > depends on these structures and is described separately or is > implicit in the structure description. > > +Before sending any group administration commands to the device, the driver > +needs to communicate to the device which commands it is going to > +use. Initially (after reset), only two commands are assumed to be used: > +VIRTIO_ADMIN_CMD_LIST_QUERY and VIRTIO_ADMIN_CMD_LIST_USE. > + > +Before sending any other commands for any member of a specific group to > +the device, the driver queries the supported commands via > +VIRTIO_ADMIN_CMD_LIST_QUERY and sends the commands it is > +capable of using via 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 > + le64 device_admin_cmd_opcodes[]; > +}; > +\end{lstlisting} > + > +This structure is an array of 64 bit values in little-endian byte > +order, in which a bit is set if the specific command opcode > +is supported. Thus, \field{device_admin_cmd_opcodes[0]} refers to the > +first 64-bit value in this array corresponding to opcodes 0 to > +63, \field{device_admin_cmd_opcodes[1]} is the second 64-bit value > +corresponding to opcodes 64 to 127, etc. > +For example, the array of size 2 including > +the values 0x3 in \field{device_admin_cmd_opcodes[0]} > +and 0x1 in \field{device_admin_cmd_opcodes[1]} indicates that only > +opcodes 0, 1 and 64 are supported. > +The length of the array depends on the supported opcodes - it is > +large enough to include bits set for all supported opcodes, > +that is the length can be calculated by starting with the largest > +supported opcode adding one, dividing by 64 and rounding up. > +In other words, for > +VIRTIO_ADMIN_CMD_LIST_QUERY and VIRTIO_ADMIN_CMD_LIST_USE the > +length of \field{command_specific_result} and > +\field{command_specific_data} respectively will be > +$DIV_ROUND_UP(max_cmd, 64) * 8$ where DIV_ROUND_UP is integer division > +with round up and \field{max_cmd} is the largest available command opcode. > + > +The array is also allowed to be larger and to additionally > +include an arbitrary number of all-zero entries. > + > +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_cmd_opcodes[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 group administration commands supported for the group type > +specified by \field{group_type}. > + > +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 group administration commands used by the driver > +with the group type specified by \field{group_type}. > + > +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 > +(for example, if the driver is not capable to use > +some required commands), the device > +completes the command with status > +VIRTIO_ADMIN_STATUS_INVALID_FIELD. > + > +Note: the driver is assumed not to set bits in > +device_admin_cmd_opcodes > +if it is not familiar with how the command opcode > +is used, since the device 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. However, for owner devices > +supporting multiple group types, the list of supported commands > +might differ between different group types. > + > \section{Administration Virtqueues}\label{sec:Basic Facilities of a Virtio Device / Administration Virtqueues} > > An administration virtqueue of an owner device is used to submit Reviewed-by: Parav Pandit <parav@nvidia.com>