Re: [Qemu-devel] [PATCH 4/4] s390x/pci: add iommu replay callback

[Cornelia Huck <cohuck@redhat.com>]

On Mon, 28 Aug 2017 10:04:47 +0200
Yi Min Zhao <zyimin@linux.vnet.ibm.com> wrote:

> Let's introduce iommu replay callback for s390 pci iommu memory region.
> Currently we don't need any dma mapping replay. So let it return
> directly. This implementation will avoid meaningless loops calling
> translation callback.
> 
> Reviewed-by: Pierre Morel <pmorel@linux.vnet.ibm.com>
> Reviewed-by: Halil Pasic <pasic@linux.vnet.ibm.com>
> Signed-off-by: Yi Min Zhao <zyimin@linux.vnet.ibm.com>
> ---
>  hw/s390x/s390-pci-bus.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
> index 9e1f7ff5c5..359509ccea 100644
> --- a/hw/s390x/s390-pci-bus.c
> +++ b/hw/s390x/s390-pci-bus.c
> @@ -407,6 +407,13 @@ static IOMMUTLBEntry s390_translate_iommu(IOMMUMemoryRegion *mr, hwaddr addr,
>      return ret;
>  }
>  
> +static void s390_pci_iommu_replay(IOMMUMemoryRegion *iommu,
> +                                  IOMMUNotifier *notifier)
> +{
> +    /* we don't need iommu replay currently */

This really needs to be heavier on the _why_. My guess is that anything
which would require replay goes through the rpcit instruction?

> +    return;
> +}
> +
>  static S390PCIIOMMU *s390_pci_get_iommu(S390pciState *s, PCIBus *bus,
>                                          int devfn)
>  {
> @@ -1055,6 +1062,7 @@ static void s390_iommu_memory_region_class_init(ObjectClass *klass, void *data)
>      IOMMUMemoryRegionClass *imrc = IOMMU_MEMORY_REGION_CLASS(klass);
>  
>      imrc->translate = s390_translate_iommu;
> +    imrc->replay = s390_pci_iommu_replay;
>  }
>  
>  static const TypeInfo s390_iommu_memory_region_info = {