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