Re: [Qemu-devel] Re: [RFC PATCH 4/7] ide: IOMMU support

[Paul Brook]

> > Depending how the we decide to handle IOMMU invalidation, it may also be
> > necessary to augment the memory_map API to allow the system to request a
> > mapping be revoked.  However this issue is not specific to the IOMMU
> > implementation. Such bugs are already present on any system that allows
> > dynamic reconfiguration of the address space, e.g. by changing PCI BARs.
> 
> That's why the memory_map API today does not allow mappings to persist
> after trips back to the main loop.

Sure it does.  If you can't combine zero-copy memory access with asynchronous 
IO then IMO it's fairly useless. See e.g. dma-helpers.c

Paul