Re: [PATCH v3 6/8] admin: Add theory of operation for write recording commands

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

On 11/15/2023 3:51 PM, Michael S. Tsirkin wrote:
> On Wed, Nov 15, 2023 at 12:05:59PM +0800, Zhu, Lingshan wrote:
> > On 11/14/2023 4:27 PM, Michael S. Tsirkin wrote:
> > > On Tue, Nov 14, 2023 at 03:34:32PM +0800, Zhu, Lingshan wrote:
> > > > > > So I can't
> > > > > > believe it has good performance overall. Logging via IOMMU or using
> > > > > > shadow virtqueue doesn't need any extra PCI transactions at least.
> > > > > On the other hand they have an extra CPU cost.  Personally if this is
> > > > > coming from a hardware vendor, I am inclined to trust them wrt PCI
> > > > > transactions.  But anyway, discussing this at a high level theoretically
> > > > > is pointless - whoever bothers with actual prototyping for performance
> > > > > testing wins, if no one does I'd expect a back of a napkin estimate
> > > > > to be included.
> > > > if so, Intel has released productions implementing these interfaces years
> > > > ago,
> > > > see live migration in 4.1. IFCVF vDPA Implementation,
> > > > https://doc.dpdk.org/guides-21.11/vdpadevs/ifc.html
> > > > and
> > > That one is based on shadow queue, right? Which I think this shows
> > > is worth supporting.
> > Yes, it is shadow virtqueue, I assume this is already mostly done,
> > do you see any gaps we need to address in our series that we should work on?
> >
> > Thanks
> There were a ton of comments posted on your series.
Hope I didn't miss anything. I see your latest comments are about vq states,
as replied before, I think we can record the states by two le16 and the 
in-flight
descriptor tracking facility.

For this shadow virtqueue, do you think I should address this in my V4?
Like saying: acknowledged control commands through the control virtqueue
should be recorded, and we want to use shadow virtqueue to track dirty 
pages.
> > > > But I still believe we are here try our best to work out an industrial spec
> > > > with better quality, to serve broad interest. This is not competition
> > > > between companies,
> > > > and the spec is not a FIFO, not like a early bird can catch all the worm.