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

[Peter Xu <peterx@redhat.com>]

On Mon, Jul 15, 2024 at 03:44:06PM +0530, Prasad Pandit wrote:
> > I remember after you added the rwlock, there's still a hang issue.
> > Did you investigated that?  Or do you mean this series will fix all the problems?
> 
> * No, this series does not fix the guest hang issue. Root cause of
> that is still a mystery. If migration is ending abruptly before all of
> the guest state is migrated, the guest hang scenario seems possible.
> Adding vhost-user-rw-lock does not address the issue of end of
> migration.

IMHO it's better we debug and fix all the issues before merging this one,
otherwise we may overlook something.  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.

> * From the protocol page above, it is not clear if the front-end
> should allow/have multiple threads talking to the same vhost-user
> device.

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.

Thanks,

-- 
Peter Xu