RE: [PATCH 1/5] Add virtio Admin Virtqueue specification

[Parav Pandit <parav@nvidia.com>]

> From: Michael S. Tsirkin <mst@redhat.com>
> Sent: Tuesday, January 18, 2022 1:36 PM

[..]
> > > > > You can map it to a queue, yes. But something static and read
> > > > > only such as list of commands maps well to config space. And
> > > > > it's not controlling one device from another, so does not really
> > > > > seem to belong in
> > > the admin queue.
> > > > >
> > > > Aq serves the writing device config too in patch-5 in this patchset.
> > >
> > > List of available admin commands does not need to be written.
> > >
> > It is not written into the aq commands.
> > It is part of the feature bit VIRTIO_F_ADMIN_PCI_VIRT_MANAGER indicating
> a given functionality supported or not in patch-5.
> 
> 
> Btw I don't see what does "VIRT_MANAGER" mean here. "manager" is just a
> generic thing that means nothing, and VIRT just repeats VIRTIO.
> 
VIRT doesn't repeat VIRTIO. VIRT indicates PCI virtual functions.
Manager is generic thing to manage.
Below is the snippet from patch-5. 

+  \item[VIRTIO_F_ADMIN_PCI_VIRT_MANAGER (44)] This feature indicates  
+ that the device can manage PCI related capabilities for its managed 
+ PCI VF  devices and supports VIRTIO_ADMIN_PCI_VIRT_MGMT_ATTR_IDENTIFY,
+  VIRTIO_ADMIN_PCI_VIRT_PROPERTY_SET and 
+ VIRTIO_ADMIN_PCI_VIRT_PROPERTY_GET
+  admin commands. This feature can be supported only by PCI devices.
+

> 
> > And structure like, virtio_admin_pci_virt_mgmt_attr_identify_result can
> potentially grow and storing those fields on on-chip resource is less efficient.
> > Hence, they are shared via AQ.
> 
> The issue is this: VIRTIO_F_ADMIN_PCI_VIRT_MANAGER seems to mean there
> are pci related admin commands. OK I guess. 
Right.
> However you then say this same
> feature bit implies generic functionality like list of supported commands.
> Confusing.
>
Not sure where I mentioned generic functionality.
This feature bit implies pci virtualization related functionality by means of above listed commands.