Re: [PATCH v2 0/3] vhost-user: Lift Max Ram Slots Limitation

[Michael S. Tsirkin]

On Sun, Feb 09, 2020 at 12:14:42PM -0500, Raphael Norwitz wrote:
> On Thu, Feb 06, 2020 at 03:33:13AM -0500, Michael S. Tsirkin wrote:
> > 
> > On Wed, Jan 15, 2020 at 09:57:03PM -0500, Raphael Norwitz wrote:
> > > 
> > > Changes since V1:
> > >     * Kept the assert in vhost_user_set_mem_table_postcopy, but moved it
> > >       to prevent corruption
> > >     * Made QEMU send a single VHOST_USER_GET_MAX_MEMSLOTS message at
> > >       startup and cache the returned value so that QEMU does not need to
> > >       query the backend every time vhost_backend_memslots_limit is called.
> > 
> > I'm a bit confused about what happens on reconnect.
> > Can you clarify pls?
> > 
> >From what I can see, backends which support reconnect call vhost_dev_init,
> which then calls vhost_user_backend_init(), as vhost-user-blk does here:
> https://github.com/qemu/qemu/blob/master/hw/block/vhost-user-blk.c#L315. The
> ram slots limit is fetched in vhost_user_backend_init() so every time the
> device reconnects the limit should be refetched. 

Right. Point is, we might have validated using an old limit.
Reconnect needs to verify limit did not change or at least
did not decrease.

-- 
MST