On 24/09/2015 06:33, 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 <da...@gibson.dropbear.id.au>
> ---
> include/exec/memory.h | 17 +++++++++++++++++
> memory.c | 18 ++++++++++++++++++
> 2 files changed, 35 insertions(+)
>
> diff --git a/include/exec/memory.h b/include/exec/memory.h
> index 5baaf48..304f985 100644
> --- a/include/exec/memory.h
> +++ b/include/exec/memory.h
> @@ -583,6 +583,23 @@ void memory_region_notify_iommu(MemoryRegion *mr,
> void memory_region_register_iommu_notifier(MemoryRegion *mr, Notifier *n);
>
> /**
> + * memory_region_register_iommu_notifier_replay: register a notifier
> + * for changes to IOMMU translation entries, and replay existing IOMMU
> + * translations to the new notifier.
> + *
> + * @mr: the memory region to observe
> + * @n: the notifier to be added; the notifier receives a pointer to an
> + * #IOMMUTLBEntry as the opaque value; the pointer ceases to be
> + * valid on exit from the notifier.
> + * @granularity: Minimum page granularity to replay notifications for
> + * @is_write: Whether to treat the replay as a translate "write"
> + * through the iommu
> + */
> +void memory_region_register_iommu_notifier_replay(MemoryRegion *mr, Notifier
> *n,
> + hwaddr granularity,
> + bool is_write);
> +
> +/**
> * memory_region_unregister_iommu_notifier: unregister a notifier for
> * changes to IOMMU translation entries.
> *
> diff --git a/memory.c b/memory.c
> index ef87363..b4b6861 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)
> +{
> + hwaddr addr;
> + IOMMUTLBEntry iotlb;
> +
> + memory_region_register_iommu_notifier(mr, n);
> +
> + for (addr = 0; addr < memory_region_size(mr); addr += granularity) {
> +
> + iotlb = mr->iommu_ops->translate(mr, addr, is_write);
> + if (iotlb.perm != IOMMU_NONE) {
> + n->notify(n, &iotlb);
> + }
> + }
> +}
If mr->size > (UINT64_MAX + 1 - granularity), you run into an infinite
loop because hwaddr is a 64bit value and the stop condition is beyond
its max value. You can avoid this by using the power of 2 of the
granularity, instead of the granularity:
int shift = ctz64(granularity);
hwaddr size = memory_region_size(mr) >> shift;
for (addr = 0; addr < size; addr++)
{
iotlb = mr->iommu_ops->translate(mr, addr << shift, is_write);
...
so in patch 6, you should pass the power of 2 instead of the value of
the granularity.
Of course, it works if granularity is at least 2....
> void memory_region_unregister_iommu_notifier(Notifier *n)
> {
> notifier_remove(n);
>
