Re: [Qemu-devel] [PATCH v3] intel_iommu: allow dynamic switch of IOMMU region

[Tian, Kevin]

> From: Peter Xu [mailto:address@hidden
> Sent: Thursday, January 05, 2017 11:53 AM
> 
> > >  /* Handle Translation Enable/Disable */
> > >  static void vtd_handle_gcmd_te(IntelIOMMUState *s, bool en)
> > >  {
> > > +    if (s->dmar_enabled == en) {
> > > +        return;
> > > +    }
> > > +
> > >      VTD_DPRINTF(CSR, "Translation Enable %s", (en ? "on" : "off"));
> > >
> > >      if (en) {
> > > @@ -1196,6 +1237,8 @@ static void vtd_handle_gcmd_te(IntelIOMMUState *s, 
> > > bool
> en)
> > >          /* Ok - report back to driver */
> > >          vtd_set_clear_mask_long(s, DMAR_GSTS_REG, VTD_GSTS_TES, 0);
> > >      }
> > > +
> > > +    vtd_switch_address_space_all(s, en);
> > >  }
> >
> > A context entry can be configured as pass-through, meaning no addr
> > translation for DMAs from this device when IOMMU is globally enabled.
> > There is no translation structure per se, so 'sys_alias" is also required
> > in such configuration.
> 
> Right. But current vt-d emulation still doesn't support per-device
> pass-through. See vtd_dev_to_context_entry():
> 
>     ...
>     } else if (ce->lo & VTD_CONTEXT_ENTRY_TT) {
>         VTD_DPRINTF(GENERAL, "error: unsupported Translation Type in "
>                     "context-entry hi 0x%"PRIx64 " lo 0x%"PRIx64,
>                     ce->hi, ce->lo);
>         return -VTD_FR_CONTEXT_ENTRY_INV;
>     }
>     ...
> 
> And:
> 
>     #define VTD_CONTEXT_ENTRY_TT        (3ULL << 2) /* Translation Type */
>     #define VTD_CONTEXT_TT_PASS_THROUGH 2
> 
> IMO we can add it when we support device passthrough.
> 

Then fine with me. :-)

Thanks
Kevin