Re: [PATCH v2 1/4] softmmu: Support concurrent bounce buffers

[Peter Xu <peterx@redhat.com>]

On Tue, Sep 05, 2023 at 09:38:39AM +0200, Mattias Nissler wrote:
> It would be nice to use a property on the device that originates the
> DMA operation to configure this. However, I don't see how to do this
> in a reasonable way without bigger changes: A typical call path is
> pci_dma_map -> dma_memory_map -> address_space_map. While pci_dma_map
> has a PCIDevice*, address_space_map only receives the AddressSpace*.
> So, we'd probably have to pass through a new QObject parameter to
> address_space_map that indicates the originator and pass that through?
> Or is there a better alternative to supply context information to
> address_space map? Let me know if any of these approaches sound
> appropriate and I'll be happy to explore them further.

Should be possible to do. The pci address space is not shared but
per-device by default (even if there is no vIOMMU intervention).  See
do_pci_register_device():

    address_space_init(&pci_dev->bus_master_as,
                       &pci_dev->bus_master_container_region, pci_dev->name);

Thanks,

-- 
Peter Xu