RE: [PATCH 3/3] hv_netvsc: Implement VF matching based on serial numbers

From: Haiyang Zhang <haiyangz@microsoft.com>
To: KY Srinivasan <kys@microsoft.com>,
	Stephen Hemminger <stephen@networkplumber.org>,
	Greg KH <gregkh@linuxfoundation.org>
Cc: "olaf@aepfle.de" <olaf@aepfle.de>,
	"jasowang@redhat.com" <jasowang@redhat.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"bjorn.helgaas@gmail.com" <bjorn.helgaas@gmail.com>,
	"apw@canonical.com" <apw@canonical.com>,
	"devel@linuxdriverproject.org" <devel@linuxdriverproject.org>,
	"leann.ogasawara@canonical.com" <leann.ogasawara@canonical.com>
Subject: RE: [PATCH 3/3] hv_netvsc: Implement VF matching based on serial numbers
Date: Fri, 16 Dec 2016 15:20:30 +0000	[thread overview]
Message-ID: <BLUPR03MB14124A002C8FA527DE7E5A9BCA9C0@BLUPR03MB1412.namprd03.prod.outlook.com> (raw)
In-Reply-To: <DM5PR03MB2490150F68D47BA025335DA2A09C0@DM5PR03MB2490.namprd03.prod.outlook.com>

> -----Original Message-----
> From: KY Srinivasan
> Sent: Thursday, December 15, 2016 8:11 PM
> To: Stephen Hemminger <stephen@networkplumber.org>; Greg KH
> <gregkh@linuxfoundation.org>
> Cc: olaf@aepfle.de; jasowang@redhat.com; linux-kernel@vger.kernel.org;
> bjorn.helgaas@gmail.com; apw@canonical.com; devel@linuxdriverproject.org;
> leann.ogasawara@canonical.com; Haiyang Zhang <haiyangz@microsoft.com>
> Subject: RE: [PATCH 3/3] hv_netvsc: Implement VF matching based on
> serial numbers
> 
> 
> 
> > -----Original Message-----
> > From: devel [mailto:driverdev-devel-bounces@linuxdriverproject.org] On
> > Behalf Of Stephen Hemminger
> > Sent: Wednesday, December 14, 2016 3:52 PM
> > To: Greg KH <gregkh@linuxfoundation.org>
> > Cc: olaf@aepfle.de; jasowang@redhat.com; linux-kernel@vger.kernel.org;
> > bjorn.helgaas@gmail.com; apw@canonical.com;
> > devel@linuxdriverproject.org; leann.ogasawara@canonical.com; Haiyang
> > Zhang <haiyangz@microsoft.com>
> > Subject: Re: [PATCH 3/3] hv_netvsc: Implement VF matching based on
> serial
> > numbers
> >
> > Normally, that would work but in this case we have one driver (netvsc)
> > which is managing another driver which is unaware of Hyper-V or netvsc
> > drivers existence.  The callback is happening in netvsc driver and it
> > needs to say "hey I know that SR-IOV device, it is associated with my
> > network device". This problem is how to know that N is associated with
> > V? The V device has to be a network device, that is easy. But then it
> > also has to be a PCI device, not to bad. But then the netvsc code
> > is matching based on hyper-V only PCI bus metadata (the serial #).
> >
> > The Microsoft developers made the rational decision not to go
> modifying
> > all the possible SR-IOV network devices from Intel and Mellanox to add
> > the functionality there. That would have been much worse.
> >
> > Maybe, rather than trying to do the management in the kernel it
> > could have been done better in user space. Unfortunately, this would
> > only move the problem.  The PCI-hyperv host driver could expose serial
> > value through sysfs (with some pain). But the problem would be how
> > to make a new API to  join the two V and N device.  Doing a private
> > ioctl is worse than the notifier.
> 
> All this has been discussed earlier in the thread. I think I have a
> solution
> to the problem:
> The only PCI (non-VF) NIC that may be present in the VM is the emulated
> NIC and
> we know exactly the device ID and vendor ID of this NIC. Furthermore,
> as a platform we are not going to be emulating additional NICs. So,
> if the PCI NIC is not the emulated NIC, it must be a VF and we can
> extract the
> serial number.

How about direct pass-through NIC devices. Do they have vPCI serial number?
And, the numbers should be different from VF NIC?

Thanks,
- Haiyang