[Xen-devel] [PATCH] xend: passthrough: check if a device is behind PCIe switch that lacks ACS

["Cui, Dexuan" <dexuan.cui@xxxxxxxxx>]

Imagine a PCIe switch, which doesn't support ACS (Access Control Services),
has 2 downstream ports: A and B, according to PCIe spec, the PCIe switch
should directly route the transaction that is from A and to a device under
B -- the Root Complex and IOMMU engine are bypassed -- this doesn't work at
all in the case of hvm guest and can even incur potential security issue, so
we should not allow such kind of device assignment.

If all the intermediate PCIe swiches between a device and Root Complex support
and enable ACS, we can safely asssign the device to guest.
Allen Kay will enable ACS later.

Thanks,
-- Dexuan

Attachment: check_dev_behind_switch.patch
Description: check_dev_behind_switch.patch

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