Re: [Qemu-ppc] [RFC PATCH qemu v3 2/4] vfio-pci: Reorder group-to-container attaching

[David Gibson]

On Sat, Apr 01, 2017 at 11:37:39PM +1100, Alexey Kardashevskiy wrote:
> At the moment VFIO PCI device initialization works as follows:
> vfio_realize
>       vfio_get_group
>               vfio_connect_container
>                       register memory listeners (1)
>                       update QEMU groups lists
>               vfio_kvm_device_add_group
> 
> Then (example for pseries) the machine reset hook triggers region_add()
> for all regions where listeners from (1) are listening:
> 
> ppc_spapr_reset
>       spapr_phb_reset
>               spapr_tce_table_enable
>                       memory_region_add_subregion
>                               vfio_listener_region_add
>                                       vfio_spapr_create_window
> 
> This scheme works fine until we need to handle VFIO PCI device hotplug
> _and_ we want to enable in-kernel acceleration on, i.e. after PCI hotplug
> we need a place to call
> ioctl(vfio_kvm_device_fd, KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE).
> Since the ioctl needs a LIOBN fd (from sPAPRTCETable) and a IOMMU group fd
> (from VFIOGroup), vfio_listener_region_add() seems to be the only place
> for this ioctl().
> 
> However this only works during boot time because the machine reset
> happens strictly after all devices are finalized. When hotplug happens,
> vfio_listener_region_add() is called when a memory listener is registered
> but when this happens:
> 1. new group is not added to the container->group_list yet;
> 2. VFIO KVM device is unaware of the new IOMMU group.
> 
> This moves bits around to have all necessary VFIO infrastructure
> in place for both initial startup and hotplug cases.
> 
> Signed-off-by: Alexey Kardashevskiy <address@hidden>

Reviewed-by: David Gibson <address@hidden>

> ---
> Changes:
> v2:
> * moved container->initialized back to its correct location
> * added missing QLIST_REMOVE()
> ---
>  hw/vfio/common.c | 19 +++++++++++--------
>  1 file changed, 11 insertions(+), 8 deletions(-)
> 
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index ab95db689c..e8188eb3d5 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -1087,6 +1087,14 @@ static int vfio_connect_container(VFIOGroup *group, 
> AddressSpace *as,
>          goto free_container_exit;
>      }
>  
> +    vfio_kvm_device_add_group(group);
> +
> +    QLIST_INIT(&container->group_list);
> +    QLIST_INSERT_HEAD(&space->containers, container, next);
> +
> +    group->container = container;
> +    QLIST_INSERT_HEAD(&container->group_list, group, container_next);
> +
>      container->listener = vfio_memory_listener;
>  
>      memory_listener_register(&container->listener, container->space->as);
> @@ -1100,14 +1108,11 @@ static int vfio_connect_container(VFIOGroup *group, 
> AddressSpace *as,
>  
>      container->initialized = true;
>  
> -    QLIST_INIT(&container->group_list);
> -    QLIST_INSERT_HEAD(&space->containers, container, next);
> -
> -    group->container = container;
> -    QLIST_INSERT_HEAD(&container->group_list, group, container_next);
> -
>      return 0;
>  listener_release_exit:
> +    QLIST_REMOVE(group, container_next);
> +    QLIST_REMOVE(container, next);
> +    vfio_kvm_device_del_group(group);
>      vfio_listener_release(container);
>  
>  free_container_exit:
> @@ -1212,8 +1217,6 @@ VFIOGroup *vfio_get_group(int groupid, AddressSpace 
> *as, Error **errp)
>  
>      QLIST_INSERT_HEAD(&vfio_group_list, group, next);
>  
> -    vfio_kvm_device_add_group(group);
> -
>      return group;
>  
>  close_fd_exit:

-- 
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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