On Thu, Dec 22, 2016 at 05:52:58PM +0800, Jason Wang wrote:
>
>
> On 2016年12月22日 17:48, Peter Xu wrote:
> > /* 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);
> > }
>
> We may need something like notifier here to tell e.g vhost to stop device
> IOTLB. (Since it's likely this series were applied after device IOTLB
> patches)
Yes, I missed vhost case.
To notify vhost, IMO we should be able to use memory listeners just
like how vfio devices do (please refer to vfio_memory_listener).
However, I think the bigger issue is we still don't have a dynamic way
to turn vhost DMAR on/off, right?
If so, we may need to re-touch all the parts to enable the dynamic
switching of DMA remapping - QEMU vhost, kernel vhost, and virtio on
the guest side... I start to doubt whether that effort will worth it
due to this single change, especially if this feature (dynamic on/off
DMA remapping) won't be used by most VMs (i.e., Linux should only turn
VT-d on when kernel detects it, and should never turn it off in
anyway).
(However I do think this is an improvement to current VT-d though)
Thanks,
-- peterx
