* Peter Xu (pet...@redhat.com) wrote:
> On Mon, Mar 05, 2018 at 05:42:42PM +0000, Dr. David Alan Gilbert wrote:
> > * Peter Xu (pet...@redhat.com) wrote:
> > > On Fri, Feb 16, 2018 at 01:16:07PM +0000, Dr. David Alan Gilbert (git)
> > > wrote:
> > >
> > > [...]
> > >
> > > > typedef struct VuVirtqElement {
> > > > diff --git a/docs/interop/vhost-user.txt b/docs/interop/vhost-user.txt
> > > > index 621543e654..bdec9ec0e8 100644
> > > > --- a/docs/interop/vhost-user.txt
> > > > +++ b/docs/interop/vhost-user.txt
> > > > @@ -682,6 +682,12 @@ Master message types
> > > > the slave must open a userfaultfd for later use.
> > > > Note that at this stage the migration is still in precopy mode.
> > > >
> > > > + * VHOST_USER_POSTCOPY_LISTEN
> > > > + Id: 27
> > > > + Master payload: N/A
> > > > +
> > > > + Master advises slave that a transition to postcopy mode has
> > > > happened.
> > >
> > > Could we add something to explain why this listen needs to be
> > > broadcasted to clients? Since I failed to find it out quickly
> > > myself. :(
> >
> > I've changed this to:
> >
> > * VHOST_USER_POSTCOPY_LISTEN
> > Id: 29
> > Master payload: N/A
> >
> > Master advises slave that a transition to postcopy mode has happened.
> > The slave must ensure that shared memory is registered with
> > userfaultfd
> > to cause faulting of non-present pages.
>
> But shouldn't this be assured by the SET_MEM_TABLE call?
Yes, it is the set_mem_table that does the register - but it only
registers it with userfaultfd if it's received a 'listen' notification,
otherwise it assumes it's a normal precopy migration.
> Sorry for being not that familiar with vhost-user protocol... but
> what's the correct order of these commands?
>
> POSTCOPY_ADVISE
> POSTCOPY_LISTEN
> SET_MEM_TABLE
Right.
Dave
> ? Thanks,
>
> >
> > This is always sent sometime after a VHOST_USER_POSTCOPY_ADVISE, and
> > thus only when VHOST_USER_PROTOCOL_F_PAGEFAULT is supported.
> >
> > Dave
> >
> > > --
> > > Peter Xu
> > --
> > Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
>
> --
> Peter Xu
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
