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

[Prasad Pandit]

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.

> 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)

Thank you.
---
  - Prasad