RE: [PATCH] VIRTIO_F_USED_EVENT_AUTO_DISABLE: add new used buffer notification suppression mechanism

Parav Pandit
2024-07-08T02:37:54Z

> From: Michael S. Tsirkin <mst@redhat.com>
> Sent: Friday, July 5, 2024 1:23 PM
>
> On Fri, Jul 05, 2024 at 04:42:52AM +0000, Parav Pandit wrote:
> > Hi Lege Wang,
> >
> >
> > > From: Lege Wang <lege.wang@jaguarmicro.com>
> > > Sent: Friday, July 5, 2024 9:05 AM
> > >
> > > hi
> > >
> > > Thanks for your comments in previous discussions.
> > > I'd like to confirm that do you understand this proposal's idea now.
> > > If yes, I may start to prepare a more formal V2.
> > >
> >
> > Notification enablement offset adjacent to current notification offset seems
> a better approach than adding the new capability for following reasons.
> >
> > 1. pci capability area (non-extended cap) is full to its capacity. New addition
> can only work in theory.
> > An obvious alternative is to add the extended cap and add there.
> > However, it is not a good idea either as the PCI spec strongly recommends
> to not keep adding vendor specific stuff in the PCI capability section.
>
> Can you point me to the relevant section in the spec?
>
Yes, the section of "DEVICE-SPECIFIC REGISTERS IN CONFIGURATION SPACE".

> > (even though an option is kept for the vendor capability).
>
> Interesting. EP guys are also asking about putting the capabilities in a BAR. So
> we might want an option to move all capabilities there.
>
> > 2. New area adjacent to current offset can further is simple enough to
> utilize.
> > There is no good reason to complicate by another extended cap.
> > If there is one, lets discuss it first.
>
> We might want to pass more data inline in the notification going forward.
> Also kick and suppression can be handled by different entities, they would
> need to be in different pages.
The kick and suppression are indeed different entities who handled.
I didn't understand the need of different pages. Most nics and storage adapters have them in single page.
Can you please explain why it should be in different page?

> Basically, don't combine unrelated things in one place.
Would like to understand if separate address is enough instead of page.

>
> --
> MST