Re: [dpdk-dev] [PATCH v7 0/5] vhost: handle memory hotplug for async vhost

[Thomas Monjalon <thomas@monjalon.net>]

23/07/2021 09:34, Xia, Chenbo:
> From: Thomas Monjalon <thomas@monjalon.net>
> > 23/07/2021 07:06, Xia, Chenbo:
> > > From: Thomas Monjalon <thomas@monjalon.net>
> > > > 22/07/2021 07:07, Xia, Chenbo:
> > > > > From: Jiang, Cheng1 <cheng1.jiang@intel.com>
> > > > > > When the guest memory is hotplugged, the vhost application which
> > > > > > enables DMA acceleration must stop DMA transfers before the vhost
> > > > > > re-maps the guest memory.
> > > > > >
> > > > > > This patch set is to provide an unsafe API to drain inflight pkts
> > > > > > which are submitted to DMA engine in vhost async data path, and
> > > > > > notify the vhost application of stopping DMA transfers. And enable it
> > > > > > in vhost example.
> > > > >
> > > > > Series applied to next-virtio/main. Thanks
> > > >
> > > > I cannot pull this series in main branch.
> > > >
> > > > There is a compilation error seen on Arm cross-compilation:
> > > >
> > > > examples/vhost/main.c:1493:51: error: assignment to 'int32_t (*)(int,
> > > > uint16_t,  struct rte_vhost_async_desc *, struct rte_vhost_async_status *,
> > > > uint16_t)' {aka 'int (*)(int,  short unsigned int,  struct
> > > > rte_vhost_async_desc *, struct rte_vhost_async_status *, short unsigned
> > int)'}
> > > > from incompatible pointer type 'uint32_t (*)(int,  uint16_t,  struct
> > > > rte_vhost_async_desc *, struct rte_vhost_async_status *, uint16_t)' {aka
> > > > 'unsigned int (*)(int,  short unsigned int,  struct rte_vhost_async_desc *,
> > > > struct rte_vhost_async_status *, short unsigned int)'} [-
> > Werror=incompatible-
> > > > pointer-types]
> > > >  1493 |                         channel_ops.transfer_data =
> > > > ioat_transfer_data_cb;
> > > >       |                                                   ^
> > >
> > > I see. @Cheng, please fix it in new version.
> > >
> > > >
> > > > Other comments about the last patch:
> > > > - it is updating doc out of the original patch doing the code changes
> > > > - there is not even a reference to the code patch (Fixes: line)
> > >
> > > I think the doc patch could be combined with the code patch in the same
> > series.
> > > But personally, sometimes I am not very clear when doc patch should be split.
> > > For example, in this case we can combine as the update in release note is
> > related
> > > only to the code patch. What if it's related to multiple patch? Should we
> > split or
> > > add doc changes to every related patches? Just a bit confused. Maybe you can
> > give
> > > me some general guidance so that we will be on the same page.
> > 
> > The doc must be updated in each patch.
> > Sometimes, the same line is updated to add a word related to the patch.
> 
> Thanks for the guidance!
> 
> > 
> > > > - the addition in the release notes is not sorted
> > >
> > > Not very clear on this. The change is put in the bottom. Is there any
> > sorting
> > > rules?
> > 
> > Read the comment at the beginning of the section, it explains
> > how things must be sorted:
> > 
> >      Suggested order in release notes items:
> >      * Core libs (EAL, mempool, ring, mbuf, buses)
> >      * Device abstraction libs and PMDs (ordered alphabetically by vendor name)
> >        - ethdev (lib, PMDs)
> >        - cryptodev (lib, PMDs)
> >        - eventdev (lib, PMDs)
> >        - etc
> >      * Other libs
> >      * Apps, Examples, Tools (if significant)
> > 
> > vhost is usually at the end of ethdev PMDs.
> 
> Oops.. I should notice it..
> 
> > 
> > > > Last question while at it, why having the API documentation
> > > > in the vhost guide (rst file)?
> > > > Doxygen is not enough to describe the functions?
> > >
> > > Good point. To be honest, I have not thought about it :P
> > >
> > > I think it could be moved to the doxygen later (maybe in another patch). The
> > only
> > > concern of mine is some API description in the vhost guide is a bit long.
> > 
> > So you can improve doxygen and remove this part of the guide.
> > The guide should be an overview, a tutorial and an internal design reference.
> 
> Make sense to me. For this patch, I suggest to keep the api doc in vhost guide.

Yes of course, don't change everything for this patch :)

> Then I will send a patch to move them all if we all agree on this.

Thank you.