Re: [Xen-devel] [PATCH v3] VT-d: fix VF of RC integrated PF matched to wrong VT-d unit

[Chao Gao <chao.gao@xxxxxxxxx>]

On Thu, Jun 29, 2017 at 04:42:33PM +0100, Roger Pau Monné wrote:
>On Thu, Jun 29, 2017 at 11:21:53AM +0800, Chao Gao wrote:
>> 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.
>> 
>> Reported-by: Crawford, Eric R <Eric.R.Crawford@xxxxxxxxx>
>> Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>
>> ---
>>  xen/drivers/passthrough/vtd/dmar.c | 11 ++++++++++-
>>  1 file changed, 10 insertions(+), 1 deletion(-)
>> 
>> diff --git a/xen/drivers/passthrough/vtd/dmar.c 
>> b/xen/drivers/passthrough/vtd/dmar.c
>> index 82040dd..27ff471 100644
>> --- a/xen/drivers/passthrough/vtd/dmar.c
>> +++ b/xen/drivers/passthrough/vtd/dmar.c
>> @@ -218,8 +218,17 @@ struct acpi_drhd_unit 
>> *acpi_find_matched_drhd_unit(const struct pci_dev *pdev)
>>      }
>>      else if ( pdev->info.is_virtfn )
>>      {
>> +        struct pci_dev *physfn;
>> +
>>          bus = pdev->info.physfn.bus;
>> -        devfn = PCI_SLOT(pdev->info.physfn.devfn) ? 0 : 
>> pdev->info.physfn.devfn;
>> +        /*
>> +         * Use 0 as 'devfn' to search VT-d unit when the physical function
>> +         * is an Extended Function.
>> +         */
>> +        pcidevs_lock();
>> +        physfn = pci_get_pdev(pdev->seg, bus, pdev->info.physfn.devfn);
>> +        pcidevs_unlock();
>> +        devfn = (physfn && physfn->info.is_extfn) ? 0 : 
>> pdev->info.physfn.devfn;
>
>AFAICT you should only release the pcidevs lock when you are done with
>the device, so that a concurrent call to pci_remove_device doesn't
>free the device while you are poking at it.

Yes. Thank you, Roger.

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