Re: [Qemu-ppc] [Qemu-devel] [RFC PATCH 05/10] memory: Allow replay of IOMMU mapping notifications

[Thomas Huth]

On 17/09/15 15:09, David Gibson wrote:
> When we have guest visible IOMMUs, we allow notifiers to be registered
> which will be informed of all changes to IOMMU mappings.  This is used by
> vfio to keep the host IOMMU mappings in sync with guest IOMMU mappings.
> 
> However, unlike with a memory region listener, an iommu notifier won't be
> told about any mappings which already exist in the (guest) IOMMU at the
> time it is registered.  This can cause problems if hotplugging a VFIO
> device onto a guest bus which had existing guest IOMMU mappings, but didn't
> previously have an VFIO devices (and hence no host IOMMU mappings).
> 
> This adds a memory_region_register_iommu_notifier_replay() function to
> handle this case.  As well as registering the new notifier it replays
> existing mappings.  Because the IOMMU memory region doesn't internally
> remember the granularity of the guest IOMMU it has a small hack where the
> caller must specify a granularity at which to replay mappings.
> 
> If there are finer mappings in the guest IOMMU these will be reported in
> the iotlb structures passed to the notifier which it must handle (probably
> causing it to flag an error).  This isn't new - the VFIO iommu notifier
> must already handle notifications about guest IOMMU mappings too short
> for it to represent in the host IOMMU.
> 
> Signed-off-by: David Gibson <address@hidden>
> ---
>  include/exec/memory.h | 16 ++++++++++++++++
>  memory.c              | 18 ++++++++++++++++++
>  2 files changed, 34 insertions(+)

> diff --git a/memory.c b/memory.c
> index 0d8b2d9..6b5a2f1 100644
> --- a/memory.c
> +++ b/memory.c
> @@ -1403,6 +1403,24 @@ void 
> memory_region_register_iommu_notifier(MemoryRegion *mr, Notifier *n)
>      notifier_list_add(&mr->iommu_notify, n);
>  }
>  
> +void memory_region_register_iommu_notifier_replay(MemoryRegion *mr, Notifier 
> *n,
> +                                                  hwaddr granularity, bool 
> is_write)

granularity itself is not an address, but a size, isn't it? So using
"hwaddr" sounds wrong here.

> +{
> +    hwaddr addr;

dma_addr_t ?

> +    IOMMUTLBEntry iotlb;
> +
> +    memory_region_register_iommu_notifier(mr, n);
> +
> +    for (addr = 0;
> +         int128_lt(int128_make64(addr), mr->size);
> +         addr += granularity) {
> +
> +        iotlb = mr->iommu_ops->translate(mr, addr, is_write);
> +        if (iotlb.perm != IOMMU_NONE)
> +            n->notify(n, &iotlb);

Missing curly braces.

> +    }
> +}
> +

 Thomas