Re: [Xen-devel] Dealing with non-existent BDF devices in VT-d and in the hardware.

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 24.03.14 at 03:37, <yang.z.zhang@xxxxxxxxx> wrote:
> Jan Beulich wrote on 2014-03-20:
>>>>> On 20.03.14 at 01:48, "Zhang, Yang Z" <yang.z.zhang@xxxxxxxxx> wrote:
>>> fake a device is a solution. But I am thinking (maybe I am wrong) why
>>> not setup all VT-d entries under a bridge if passing a PCI device under
>>> a bridge. Because when passing a PCI device under a bridge, all devices
>>> under bridge should be assigned to the guest too. What current Xen dose
>>> is only set the entry which has device, so why not extend it to setup
>>> all entries? In this case, there is no user input is required.
>> 
>> You'd have to prove that this doesn't impact isolation/security.
> 
> Yes, this need more deeply think. 
> 
> BTW, do you see any potential issue with doing this?

Not a concrete one - I simply think that security/isolation guarantees
are easier to validate if permissions for a guest are kept to the smallest
possible set. So without full proof of the security of above concept I
think we should accept the new behavior only as an opt-in (via
command line or domain config option).

Jan


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