Re: [PATCH v6 06/10] x86/mem-sharing: copy GADDR based shared guest areas

["Roger Pau Monné" <roger.pau@citrix.com>]

On Mon, Oct 16, 2023 at 11:55:25AM +0200, Jan Beulich wrote:
> On 04.10.2023 15:53, Roger Pau Monne wrote:
> > @@ -1950,7 +1978,15 @@ int mem_sharing_fork_reset(struct domain *d, bool reset_state,
> >  
> >   state:
> >      if ( reset_state )
> > +    {
> >          rc = copy_settings(d, pd);
> > +        if ( rc == -ERESTART )
> > +            /*
> > +             * Translate to -EAGAIN, see TODO comment at top of function about
> > +             * hypercall continuations.
> > +             */
> > +            rc = -EAGAIN;
> > +    }
> 
> Are existing callers known to properly handle EAGAIN? I'm worried of the
> verbosity that was no lost here.

No idea about the callers using XENMEM_sharing_op_fork_reset, but it
did seem the best option rather than leaking -ERESTART to callers.  We
have no callers of xc_memshr_fork_reset() in the tree.

vm_event_resume() will trigger an assert if mem_sharing_fork_reset()
fails with any error code, so doesn't make much difference there if
the return is -EAGAIN or -ERESTART.

My initial proposal had -EBUSY IIRC.

Thanks, Roger.