Re: [virtio-comment] Re: [PATCH 0/2] Selective queue enabling

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Jun 13, 2023 at 12:12:43PM +0200, Eugenio Perez Martin wrote:
> On Tue, Jun 13, 2023 at 9:53âAM Michael S. Tsirkin <mst@redhat.com> wrote:
> >
> > On Tue, Jun 13, 2023 at 03:46:35AM -0400, Michael S. Tsirkin wrote:
> > > On Mon, Jun 12, 2023 at 09:56:57AM +0200, Eugenio Perez Martin wrote:
> > > > > > Another drawback of that is the long time a device can spend to
> > > > > > reconfigure its memory maps.
> > > > >
> > > > > The map is already used for cvq though, I don't see why it would take
> > > > > much more with this.
> > > > >
> > > >
> > > > In the case of vDPA HW, CVQ maps may not need to reach the device's or
> > > > platform IOMMU, so the modification of that mapping is way cheaper.
> > >
> > > Oh, I get it. It's setup time, but you are right.
> > >
> > > > > > taking that into account, does it make
> > > > > > sense to send a new version with the bit 1 on enable?
> > > > > >
> > > > > > Thanks!
> > > > >
> > > > > Current hardware won't support the extra bit though.
> >
> >
> > Thinking more about this, I think the following works:
> >
> > - enable all queues before DRIVER_OK
> > - reset all data queues before DRIVER_OK
> > - DRIVER_OK
> > - CVQ commands
> > - re-enable data queues
> >
> >
> > No?
> >
> 
> If it is valid to write to queue_reset before DRIVER_OK, then sure. I
> asked for that in the past at
> https://lists.oasis-open.org/archives/virtio-dev/202305/msg00329.html
> .

Well then Jason said:
 we should make svq work without RING_RESET
but now apparently we went full circle and propose
a feature bit after all?


> >
> >
> > > --
> > > MST
> >
> >
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