[Xen-devel] Dom0 hypercall for adding and removing PCI devices

["Han, Weidong" <weidong.han@xxxxxxxxx>]

Now dom0 uses hypercalls to add and remove PCI devices. In
pci_bus_probe_wrapper(), it firstly adds device, then use
pci_bus_probe() to probe it, remove the device if probe fails. The
approach is good to only assign workable devices (pci_bus_probe()
successes) to dom0, but it obviously misses RMRR. During dom0 booting,
BIOS will use RMRRs. If don't map RMRRs, system will hang. There are two
options:

1) Add a check in domain_context_unmap_one(), don't remove the device
from dom0 if it has RMRR. This check is added yesterday. But it's not
clean enough. The device is not assigned to dom0, while it is mapped in
dom0 VT-d page table.

2) Establish a separate RMRR page table. If the device with RMRR is
removed from dom0, unmap it from dom0 VT-d page table, instead map it to
the separate RMRR page table. This solution is clean, but it introduces
a new VT-d page table. Currently each domain has only one VT-d page
table.

What's your opinions?

Randy (Weidong) 

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