Re: proposal: use admin command (and aq) of the device to query config space

["Zhu, Lingshan" <lingshan.zhu@intel.com>]

On 8/2/2023 4:59 PM, Parav Pandit wrote:
> > From: Zhu, Lingshan <lingshan.zhu@intel.com>
> > Sent: Wednesday, August 2, 2023 2:15 PM
> > Rebasing "transport vq" on admin vq is still in my pipeline, I am currently
> > working on a patch series implementing virtio pci live migration in the
> > spec(carry on Jason and Eugenio's work).
> > I will post it next week and back to transport vq task then.
> Awesome and interesting to us as well.
> I have draft for member device migration admin commands.
> I guess yours will hit the mailing list first, so we can converge on your series.
OK
> > For SIOV, I have implemented the interfaces for querying the configurations, for
> > example:
> > 1) Access config space:
> >
> > 247 +\begin{lstlisting}
> > 248 +#define VIRTIO_TRANSPTQ_CTRL_CONFIGÂÂÂ 6
> > 249 +Â #define VIRTIO_TRANSPTQ_CTRL_CONFIG_GETÂÂÂ 0
> > 250 +Â #define VIRTIO_TRANSPTQ_CTRL_CONFIG_SETÂÂÂ 1
> > 251 +
> > 252 +struct virtio_transportq_ctrl_dev_config_get {
> > 253 +ÂÂÂÂÂÂ u32 offset;
> > 254 +ÂÂÂÂÂÂ u32 size;
> > 255 +};
> > 256 +
> > 257 +struct virtio_transportq_ctrl_dev_config_set {
> > 258 +ÂÂÂÂÂÂ u32 offset;
> > 259 +ÂÂÂÂÂÂ u32 size;
> > 260 +ÂÂÂÂÂÂ u8Â data[];
> > 261 +};
> > 262 +\end{lstlisting}
> >
> > I think we can re-use the GET command for SR-IOV, I am afraid SET would be a
> > side-channel attacking surface for SR-IOV.
> Get and set both should be inband for PF, VF, SIOV.
> I donât see any need to diverge and create any weird combinations differently for 3 different device types.
I am not sure, when passthrough a device to a guest, the guest driver 
ownes the config space of the device,
if we allow changes against the config space through admin vq from host, 
it looks like a risk.
> > 2) a specific config, e.g., features:
> >
> > 142 +The features negotiation of managed devices is done by the
> > 143 +following commands:
> > 144 +
> > 145 +\begin{lstlisting}
> > 146 +#define VIRTIO_TRANSPTQ_CTRL_FEATÂÂ 3
> > 147 + #define VIRTIO_TRANSPTQ_CTRL_FEAT_DEVICE_GETÂÂÂÂÂÂÂ 0
> > 148 + #define VIRTIO_TRANSPTQ_CTRL_FEAT_DRIVER_SETÂÂÂÂÂÂÂ 1
> > 149 + #define VIRTIO_TRANSPTQ_CTRL_FEAT_DRIVER_GETÂÂÂÂÂÂÂ 2
> > 150 +
> > 151 +struct virtio_transportq_ctrl_dev_features {
> > 152 +ÂÂÂÂÂÂÂ u32 features_len;
> > 153 +ÂÂÂÂÂÂÂ u32 features[features_len];
> > 154 +};
> > 155 +\end{lstlisting}
> >
> > still can re-use the GET commands.
> >
> > Thanks
> > Zhu Lingshan