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.
-
>
> return;
> }
>
