Re: [Xen-devel] [PATCH v9 5/5] x86/ioreq server: Synchronously reset outstanding p2m_ioreq_server entries when an ioreq server unmaps.

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: Wednesday, March 22, 2017 4:54 PM
> 
> >>> On 22.03.17 at 09:28, <kevin.tian@xxxxxxxxx> wrote:
> >>  From: Yu Zhang
> >> Sent: Tuesday, March 21, 2017 10:53 AM
> >> --- a/xen/arch/x86/hvm/dm.c
> >> +++ b/xen/arch/x86/hvm/dm.c
> >> @@ -385,16 +385,51 @@ static int dm_op(domid_t domid,
> >>
> >>      case XEN_DMOP_map_mem_type_to_ioreq_server:
> >>      {
> >> -        const struct xen_dm_op_map_mem_type_to_ioreq_server *data =
> >> +        struct xen_dm_op_map_mem_type_to_ioreq_server *data =
> >>              &op.u.map_mem_type_to_ioreq_server;
> >> +        unsigned long first_gfn = data->opaque;
> >> +        unsigned long last_gfn;
> >> +
> >> +        const_op = false;
> >>
> >>          rc = -EOPNOTSUPP;
> >>          /* Only support for HAP enabled hvm. */
> >>          if ( !hap_enabled(d) )
> >>              break;
> >>
> >> -        rc = hvm_map_mem_type_to_ioreq_server(d, data->id,
> >> -                                              data->type, data->flags);
> >> +        if ( first_gfn == 0 )
> >> +            rc = hvm_map_mem_type_to_ioreq_server(d, data->id,
> >> +                                                  data->type, 
> >> data->flags);
> >> +        /*
> >> +         * Iterate p2m table when an ioreq server unmaps from
> >> p2m_ioreq_server,
> >> +         * and reset the remaining p2m_ioreq_server entries back to
> >> p2m_ram_rw.
> >> +         */
> >
> > can you elaborate how device model is expected to use this new
> > extension, i.e. on deciding first_gfn?
> 
> The device model doesn't decide anything here (hence the field's name being
> "opaque"), it simply has to pass zero for correct operation.
> 

Got it. It's for hypercall continuation. :-)

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