Re: [PATCH v5 3/7] Introduce new destination type for admin commands

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

On Wed, Apr 27, 2022 at 01:58:20AM +0300, Max Gurtovoy wrote:
> Introduce a new mechanism to issue commands with dst_type field that is
> not "self". With the new mechanism, driver can set dst_type to 1
> and use the vdev_id common field to describe the designated vdev_id.
> 
> This mechanism is useful for device groups with multiple devices
> with various different capabilities. For example, a type 1 device group
> that contains a PCI PF and its VF. For this group, a clever system
> administrator can use admin commands to manipulate the PF/VF resources.
> 
> Reviewed-by: Parav Pandit <parav@nvidia.com>
> Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
> ---
>  admin.tex | 18 ++++++++++++++----
>  1 file changed, 14 insertions(+), 4 deletions(-)
> 
> diff --git a/admin.tex b/admin.tex
> index 6725daa..f816c3b 100644
> --- a/admin.tex
> +++ b/admin.tex
> @@ -11,11 +11,13 @@ \section{Administration command set}\label{sec:Basic Facilities of a Virtio Devi
>          le16 command;
>          /*
>           * 0 - self
> -         * 1 - 65535 are reserved
> +         * 1 - other virtio device (identified by vdev_id) in the same device group
> +         * 2 - 65535 are reserved
>           */
>          le16 dst_type;
> +        le64 vdev_id;

Alignment problems. Proposal:

vdev_id
dst_type
command



>          /* reserved for common cmd fields */
> -        u8 reserved[20];
> +        u8 reserved[12];
>          u8 command_specific_data[];
>  
>          /* Device-writable part */


> @@ -39,9 +41,11 @@ \section{Administration command set}\label{sec:Basic Facilities of a Virtio Devi
>  \hline
>  03h   & VIRTIO_ADMIN_STATUS_INVALID_FIELD    & invalid field was set  \\
>  \hline
> +04h   & VIRTIO_ADMIN_STATUS_INVALID_VDEV_ID    & invalid vdev_id was set  \\
> +\hline
>  \end{tabular}
>  
> -The \field{command}, \field{dst_type} and \field{command_specific_data} are
> +The \field{command}, \field{dst_type}, \field{vdev_id} and \field{command_specific_data} are
>  set by the driver, and the device sets the \field{status}, the
>  \field{command_specific_error} and the \field{command_specific_result},
>  if needed.
> @@ -50,9 +54,15 @@ \section{Administration command set}\label{sec:Basic Facilities of a Virtio Devi
>  
>  The mandatory fields to be set by the driver, for all admin commands, are \field{command} and \field{dst_type}.
>  
> +The optional unused fields to be zeroed by the driver.
> +
>  The \field{command} defines the opcode for the command. The value for each command can be found in each command section.
>  
> -The \field{dst_type} defines the designated virtio device for the command. This value should be set to 0 (self).
> +The \field{dst_type} defines the designated virtio device for the command. This value can be set to 0 (self) or 1 (other virtio device in the same device
> +group) by the driver. Not all the commands allow setting \field{dst_type} to 1. Refer to each command description explicitly to check whether this operation is allowed.
> +If \field{dst_type} is set to 0 by the driver, the \field{vdev_id} isn't valid, should be zeroed by the driver and should be ignored by the device.
> +If \field{dst_type} is set to 1 by the driver, the \field{vdev_id} is valid and used to describe the vdev_id of the designated virtio device (see section
> +\ref{sec:Introduction / Terminology / Device group} for vdev_id numbering for type 1 device groups).
>  
>  The \field{command_specific_error} should be inspected by the driver only if \field{status} is set to
>  VIRTIO_ADMIN_STATUS_CS_ERR by the device. In this case, the content of \field{command_specific_error}


teminology is a bit inconsistent. would dst_id be better? it goes
together with dst_type after all.

> -- 
> 2.21.0