On Wed, May 18, 2022 at 05:34:33PM +0300, Max Gurtovoy wrote:
>
> On 5/15/2022 6:09 PM, Michael S. Tsirkin wrote:
>
> 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 <>
> >
> Signed-off-by: Max Gurtovoy <>
> > > ---
> >
>
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
>
> I don't understand what is the issue here. All sw-hw packets should be
> __packed__
No and most virtio ones are not.
> why should I change the order to be something that is not intuitive ?
packed structs often cause compiler to generate horrible code.
so we generally don't do this. in some cases we made a mistake
and stick to it for now. don't copy that.
> >
> >
> > >
/* 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.
>
> I don't think dst_id is better than vdev_id. Sorry.
>
> vdev_id is a unique identifier of a device inside a device group.
- no consistency with dst_type
- v in "vdev" is pointless
- does not tell you which device it is. source sending command?
destination to which it refers?
> >
> > > --
> >
> 2.21.0
