Re: [Qemu-devel] [RFC PATCH qemu] exec: Destroy dispatch immediately

[Peter Maydell]

On 25 August 2017 at 14:19, David Gibson <address@hidden> wrote:
> Hm.  Why do we need to construct full ASes for virtio-blk, rather than
> just MRs?

It's the PCI layer that's doing it, but the overall reason is because
virtio-blk needs to make memory transactions (DMA reads and writes).
The AddressSpace is our construct for "thing you use to be able
to efficiently make memory transactions on a MemoryRegion".
(This is what the FlatView and AddressSpaceDispatch data structures
are for -- they let you efficiently go from "write to address 0x4000
in this thing" to the actual destination RAM or device read/write
pointers.)

thanks
-- PMM