Re: [Qemu-devel] [PATCH v3 08/12] hw/pci: introduce pci_device_notify_iommu()

[Paolo Bonzini]

On 01/03/2018 11:33, Liu, Yi L wrote:
> This patch adds pci_device_notify_iommu() for notify virtual IOMMU
> emulator when assigned device is added. And adds a new notify_func
> in PCIBus. vIOMMU emulator provides the instance of this notify_func.
> 
> Reason:
> When virtual IOMMU is exposed to guest, vIOMMU emulator needs to
> programm host IOMMU to setup DMA mapping for assigned devices. This
> is a per-device operation, to be efficient, vIOMMU emulator needs
> to record the assigned devices.
> 
> Example: devices assigned thru vfio, vfio_realize would call
> pci_device_notify_iommu() to notify vIOMMU emulator to record necessary
> info for assigned device.

I think the notification should not be left to the individual device.
Instead, the add notification should be done in pci_setup_sva_ops, and
the delete notification should be done in pci_qdev_unrealize, before
calling pc->exit, and only if dev->sva_ops is not NULL.

In general I think it's better to change your names from "assigned_dev"
to "sva_dev", because the point of the list is to only iterate over
devices that might be interested in using SVA.

Paolo