Re: [Xen-devel] [PATCH v4] VT-d: fix VF of RC integrated PF matched to wrong VT-d unit

[Chao Gao <chao.gao@xxxxxxxxx>]

On Fri, Jun 30, 2017 at 05:19:52PM +0800, Tian, Kevin wrote:
>> From: Gao, Chao
>> Sent: Friday, June 30, 2017 9:17 AM
>> 
>> The problem is for a VF of RC integrated PF (e.g. PF's BDF is 00:02.0),
>> we would wrongly use 00:00.0 to search VT-d unit.
>> 
>> From SRIOV spec REV 1.0 section 3.7.3, it says:
>> "ARI is not applicable to Root Complex integrated Endpoints; all other
>> SR-IOV Capable Devices (Devices that include at least one PF) shall
>> implement the ARI Capability in each Function.". So PFs can be classified to
>> two kinds: one is RC integrated PF and the other is non-RC integrated PF. The
>> former can't support ARI and the latter shall support ARI. For Extended
>> Functions, one traditional function's BDF should be used to search VT-d unit.
>> And according to PCIe spec, Extened Function means within an ARI device, a
>> Function whose Function Number is greater than 7. Thus, the former can't be
>> an
>> extended function, while the latter is as long as its devfn > 7, this check 
>> is
>> exactly what the original code did; The original code wasn't aware the 
>> former.
>> 
>> This patch directly looks up the 'is_extfn' field of PF's struct pci_dev
>> to decide whether the PF is a extended function.
>
>Above description looks like the bug is caused by ARI problem. But
>if you look at the original code (and the problem you described), it's
>not related to ARI. ARI comes just when adding a clean fix, so please 
>revise the description to make that part clear
>

How about this:

The problem is for a VF of RC integrated PF (e.g. PF's BDF is 00:02.0),
we would wrongly use 00:00.0 to search VT-d unit.

If a PF is an extended function, a traditional function's BDF should be
used to search VT-d unit. Previous code only checks whether Function
Number is greater than 7, without checking the prerequisite that the
function should be within an ARI device. This incurs wrongly using
traditional function's BDF when the PF is RC integrated and thus cannot
be within an ARI device.

Considering 'is_extfn' field of struct pci_dev has been passed down from
Domain0 to indicate whether the function is an extended function, this
patch just looks up that field of PF's struct pci_dev and adjust BDF
used to search VT-d unit accordingly. 

Thanks
Chao

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