On Wed, Sep 30, 2015 at 11:09:17AM +0200, Laurent Vivier wrote:
>
>
> On 30/09/2015 04:13, David Gibson wrote:
> > At present the memory listener used by vfio to keep host IOMMU mappings
> > in sync with the guest memory image assumes that if a guest IOMMU
> > appears, then it has no existing mappings.
> >
> > This may not be true if a VFIO device is hotplugged onto a guest bus
> > which didn't previously include a VFIO device, and which has existing
> > guest IOMMU mappings.
> >
> > Therefore, use the memory_region_register_iommu_notifier_replay()
> > function in order to fix this case, replaying existing guest IOMMU
> > mappings, bringing the host IOMMU into sync with the guest IOMMU.
> >
> > Signed-off-by: David Gibson <da...@gibson.dropbear.id.au>
> > ---
> > hw/vfio/common.c | 23 +++++++++--------------
> > 1 file changed, 9 insertions(+), 14 deletions(-)
> >
> > diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> > index f666de2..6797208 100644
> > --- a/hw/vfio/common.c
> > +++ b/hw/vfio/common.c
> > @@ -312,6 +312,11 @@ out:
> > rcu_read_unlock();
> > }
> >
> > +static hwaddr vfio_container_granularity(VFIOContainer *container)
> > +{
> > + return (hwaddr)1 << ctz64(container->iova_pgsizes);
> > +}
> > +
> > static void vfio_listener_region_add(MemoryListener *listener,
> > MemoryRegionSection *section)
> > {
> > @@ -369,26 +374,16 @@ static void vfio_listener_region_add(MemoryListener
> > *listener,
> > * would be the right place to wire that up (tell the KVM
> > * device emulation the VFIO iommu handles to use).
> > */
> > - /*
> > - * This assumes that the guest IOMMU is empty of
> > - * mappings at this point.
> > - *
> > - * One way of doing this is:
> > - * 1. Avoid sharing IOMMUs between emulated devices or different
> > - * IOMMU groups.
> > - * 2. Implement VFIO_IOMMU_ENABLE in the host kernel to fail if
> > - * there are some mappings in IOMMU.
> > - *
> > - * VFIO on SPAPR does that. Other IOMMU models may do that
> > different,
> > - * they must make sure there are no existing mappings or
> > - * loop through existing mappings to map them into VFIO.
> > - */
> > giommu = g_malloc0(sizeof(*giommu));
> > giommu->iommu = section->mr;
> > giommu->container = container;
> > giommu->n.notify = vfio_iommu_map_notify;
> > QLIST_INSERT_HEAD(&container->giommu_list, giommu, giommu_next);
> > +
> > memory_region_register_iommu_notifier(giommu->iommu, &giommu->n);
> > + memory_region_iommu_replay(giommu->iommu, &giommu->n,
> > + vfio_container_granularity(container),
> > + false);
>
> I'm wondering if it has any sense to provide the "is_write" information
> at this level of the API: I don't think we can have access to this
> information when we call this function (so it will be always used with
> false, or called twice once with false, once with true). I think it
> would be better to manage this internally.
I agree it's pretty ugly, but I'm not really sure how to handle it
better. The translate function itself wants is_write; I'm pretty sure
"false" is the right thing here, but I'm not sure it would be right
for all potential replay cases.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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