Re: [Qemu-devel] [PATCH qemu v14 16/18] spapr_iommu, vfio, memory: Notify IOMMU about starting/stopping being used by VFIO

[David Gibson <david@gibson.dropbear.id.au>]

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On Mon, Mar 21, 2016 at 06:47:04PM +1100, Alexey Kardashevskiy wrote:
> The sPAPR TCE tables manage 2 copies when VFIO is using an IOMMU -
> a guest view of the table and a hardware TCE table. If there is no VFIO
> presense in the address space, then just the guest view is used, if
> this is the case, it is allocated in the KVM. However since there is no
> support yet for VFIO in KVM TCE hypercalls, when we start using VFIO,
> we need to move the guest view from KVM to the userspace; and we need
> to do this for every IOMMU on a bus with VFIO devices.
> 
> This adds vfio_start/vfio_stop callbacks in MemoryRegionIOMMUOps to
> notifiy IOMMU about changing environment so it can reallocate the table
> to/from KVM or (when available) hook the IOMMU groups with the logical
> bus (LIOBN) in the KVM.
> 
> This removes explicit spapr_tce_set_need_vfio() call from PCI hotplug
> path as the new callbacks do this better - they notify IOMMU at
> the exact moment when the configuration is changed, and this also
> includes the case of PCI hot unplug.
> 
> TODO: split into 2 or 3 patches, per maintainership area.
> 
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>

I'm finding this one much easier to follow than the previous revision.

> ---
>  hw/ppc/spapr_iommu.c  | 12 ++++++++++++
>  hw/ppc/spapr_pci.c    |  6 ------
>  hw/vfio/common.c      |  9 +++++++++
>  include/exec/memory.h |  4 ++++
>  4 files changed, 25 insertions(+), 6 deletions(-)
> 
> diff --git a/hw/ppc/spapr_iommu.c b/hw/ppc/spapr_iommu.c
> index 6dc3c45..702075d 100644
> --- a/hw/ppc/spapr_iommu.c
> +++ b/hw/ppc/spapr_iommu.c
> @@ -151,6 +151,16 @@ static uint64_t spapr_tce_get_page_sizes(MemoryRegion *iommu)
>      return 1ULL << tcet->page_shift;
>  }
>  
> +static void spapr_tce_vfio_start(MemoryRegion *iommu)
> +{
> +    spapr_tce_set_need_vfio(container_of(iommu, sPAPRTCETable, iommu), true);
> +}
> +
> +static void spapr_tce_vfio_stop(MemoryRegion *iommu)
> +{
> +    spapr_tce_set_need_vfio(container_of(iommu, sPAPRTCETable, iommu), false);
> +}

Wonder if a single callback which takes a boolean might be a little
less clunky.

>  static void spapr_tce_table_do_enable(sPAPRTCETable *tcet);
>  static void spapr_tce_table_do_disable(sPAPRTCETable *tcet);
>  
> @@ -211,6 +221,8 @@ static const VMStateDescription vmstate_spapr_tce_table = {
>  static MemoryRegionIOMMUOps spapr_iommu_ops = {
>      .translate = spapr_tce_translate_iommu,
>      .get_page_sizes = spapr_tce_get_page_sizes,
> +    .vfio_start = spapr_tce_vfio_start,
> +    .vfio_stop = spapr_tce_vfio_stop,
>  };
>  
>  static int spapr_tce_table_realize(DeviceState *dev)
> diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
> index bfcafdf..af99a36 100644
> --- a/hw/ppc/spapr_pci.c
> +++ b/hw/ppc/spapr_pci.c
> @@ -1121,12 +1121,6 @@ static void spapr_phb_add_pci_device(sPAPRDRConnector *drc,
>      void *fdt = NULL;
>      int fdt_start_offset = 0, fdt_size;
>  
> -    if (object_dynamic_cast(OBJECT(pdev), "vfio-pci")) {
> -        sPAPRTCETable *tcet = spapr_tce_find_by_liobn(phb->dma_liobn);
> -
> -        spapr_tce_set_need_vfio(tcet, true);
> -    }
> -
>      if (dev->hotplugged) {
>          fdt = create_device_tree(&fdt_size);
>          fdt_start_offset = spapr_create_pci_child_dt(phb, pdev, fdt, 0);
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index b257655..4e873b7 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -421,6 +421,9 @@ static void vfio_listener_region_add(MemoryListener *listener,
>          QLIST_INSERT_HEAD(&container->giommu_list, giommu, giommu_next);
>  
>          memory_region_register_iommu_notifier(giommu->iommu, &giommu->n);
> +        if (section->mr->iommu_ops && section->mr->iommu_ops->vfio_start) {
> +            section->mr->iommu_ops->vfio_start(section->mr);
> +        }
>          memory_region_iommu_replay(giommu->iommu, &giommu->n,
>                                     false);
>  
> @@ -466,6 +469,7 @@ static void vfio_listener_region_del(MemoryListener *listener,
>      VFIOContainer *container = container_of(listener, VFIOContainer, listener);
>      hwaddr iova, end;
>      int ret;
> +    MemoryRegion *iommu = NULL;
>  
>      if (vfio_listener_skipped_section(section)) {
>          trace_vfio_listener_region_del_skip(
> @@ -487,6 +491,7 @@ static void vfio_listener_region_del(MemoryListener *listener,
>          QLIST_FOREACH(giommu, &container->giommu_list, giommu_next) {
>              if (giommu->iommu == section->mr) {
>                  memory_region_unregister_iommu_notifier(&giommu->n);
> +                iommu = giommu->iommu;
>                  QLIST_REMOVE(giommu, giommu_next);
>                  g_free(giommu);
>                  break;
> @@ -519,6 +524,10 @@ static void vfio_listener_region_del(MemoryListener *listener,
>                       "0x%"HWADDR_PRIx") = %d (%m)",
>                       container, iova, end - iova, ret);
>      }
> +
> +    if (iommu && iommu->iommu_ops && iommu->iommu_ops->vfio_stop) {
> +        iommu->iommu_ops->vfio_stop(section->mr);
> +    }

IIRC there can be multiple containers listening on the same PCI
address space.  In that case, this won't be correct, because once one
of the VFIO containers is removed, it will call vfio_stop, even though
the other VFIO container still needs the guest IOMMU to support it.

So I think you need some sort of refcounting here.

>  }
>  
>  static const MemoryListener vfio_memory_listener = {
> diff --git a/include/exec/memory.h b/include/exec/memory.h
> index eb5ce67..f1de133f 100644
> --- a/include/exec/memory.h
> +++ b/include/exec/memory.h
> @@ -152,6 +152,10 @@ struct MemoryRegionIOMMUOps {
>      IOMMUTLBEntry (*translate)(MemoryRegion *iommu, hwaddr addr, bool is_write);
>      /* Returns supported page sizes */
>      uint64_t (*get_page_sizes)(MemoryRegion *iommu);
> +    /* Called when VFIO starts using this */
> +    void (*vfio_start)(MemoryRegion *iommu);
> +    /* Called when VFIO stops using this */
> +    void (*vfio_stop)(MemoryRegion *iommu);
>  };
>  
>  typedef struct CoalescedMemoryRange CoalescedMemoryRange;

-- 
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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