Re: [PATCH 0/2] Postcopy migration and vhost-user errors

[Peter Xu]

On Tue, Jul 16, 2024 at 03:44:54PM +0530, Prasad Pandit wrote:
> Hello Peter,
> 
> On Mon, 15 Jul 2024 at 19:10, Peter Xu <peterx@redhat.com> wrote:
> > IMHO it's better we debug and fix all the issues before merging this one,
> > otherwise we may overlook something.
> 
> * Well we don't know where the issue is, not sure where the fix may go
> in, ex. if the issue turns out to be how virsh(1) invokes
> migrate-postcopy, fix may go in virsh(1). Patches in this series
> anyway don't help to fix the migration convergence issue, so they
> could be reviewed independently I guess.

I still think we should find a complete solution before merging anything,
because I'm not 100% confident the issue to be further investigated is
irrelevant to this patch.

No strong opinions, I'll leave that to Michael to decide.

> 
> > You could pass over the patch to whoever going to debug this, so it will be 
> > included in the whole set to be
> > posted when the bug is completely fixed.
> 
> * Yes, this patch series is linked there.
> 
> > The protocol should have no restriction on the thread model of a front-end.
> > It only describes the wire protocol.
> >
> > IIUC the protocol was designed to be serialized by nature (where there's no
> > request ID, so we can't match reply to any of the previous response), then
> > the front-end can manage the threads well to serialize all the requests,
> > like using this rwlock.
> 
> * I see, okay. The simple protocol definition seems to indicate that
> it is meant for one front-end/back-end pair. If we are dividing the
> front-end across multiple threads, maybe we need a document to
> describe those threads and how they work, at least for the QEMU
> (front-end) side. Because the back-end could be a non-QEMU process, we
> can not do much there. (just thinking)

IMHO that's not part of the protocol but impl details, so the current doc
looks all fine to me.

Thanks,

-- 
Peter Xu