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

[Chao Gao <chao.gao@xxxxxxxxx>]

On Mon, Jun 19, 2017 at 01:43:25AM -0600, Jan Beulich wrote:
>>>> On 19.06.17 at 08:33, <chao.gao@xxxxxxxxx> wrote:
>> On Fri, Jun 16, 2017 at 09:52:11AM -0600, Jan Beulich wrote:
>>>>>> On 16.06.17 at 08:48, <chao.gao@xxxxxxxxx> wrote:
>>>> The problem is 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.
>>>> 
>>>> To search VT-d unit for a VF, the BDF of the PF is used. And If the
>>>> PF is an Extended Function, the BDF of one traditional function is
>>>> used. The following line (from acpi_find_matched_drhd_unit()):
>>>>     devfn = PCI_SLOT(pdev->info.physfn.devfn) ? 0 : 
>>>> pdev->info.physfn.devfn;
>>>> sets 'devfn' to 0 if PF's devfn > 8.
>>>
>>>Is that really the relevant line? Since you say PF is an Extended
>>>Function, wouldn't
>>>
>>>    if ( pdev->info.is_extfn )
>>>    {
>>>        bus = pdev->bus;
>>>        devfn = 0;
>>>    }
>>>
>>>be the relevant code? Or else - is is_extfn not being set correctly?
>> 
>> I think this field is not being set for VF. And here what we want to
>> know is whether the PF of this VF is an extended functin. We also can add
>> a new field 'is_extfn' in pdev->info.physfn and change the caller in
>> linux kernel accordingly. But it will be not compatible with the old kernel.
>
>Wait, no - I did describe things slightly wrongly, and hence perhaps
>managed to confuse you (besides myself). For the VF we don't want
>to see is_extfn set, but for its PF I'd expect that to be the case.
>With that I'd then think looking up the struct pci_dev for the PF is all
>it takes to tell apart both cases, the more that I'm not sure ...

Hi, Jan. in pci_add_device():

    else if (info->is_virtfn)
    {
        pcidevs_lock();
        pdev = pci_get_pdev(seg, info->physfn.bus, info->physfn.devfn);
        pcidevs_unlock();
        if ( !pdev )
            pci_add_device(seg, info->physfn.bus, info->physfn.devfn,
                           NULL, node);
        pdev_type = "virtual function";
    }

could you recall in which case, we can't get the PF by
pci_get_pdev() above? The reason why I want to know is in this case,
is_extfn of the PF may not be set correctly.

Thanks
Chao

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