RE: [PATCH net-next] hv_netvsc: fix vf serial matching with pci slot info

[Haiyang Zhang]

> -----Original Message-----
> From: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>
> Sent: Friday, October 12, 2018 2:36 AM
> To: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
> Cc: davem@xxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; olaf@xxxxxxxxx; Stephen
> Hemminger <sthemmin@xxxxxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx;
> devel@xxxxxxxxxxxxxxxxxxxxxx; vkuznets <vkuznets@xxxxxxxxxx>
> Subject: Re: [PATCH net-next] hv_netvsc: fix vf serial matching with pci slot info
> 
> On Thu, Oct 11, 2018 at 08:14:34PM +0000, Haiyang Zhang wrote:
> > From: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
> >
> > The VF device's serial number is saved as a string in PCI slot's kobj
> > name, not the slot->number. This patch corrects the netvsc driver, so
> > the VF device can be successfully paired with synthetic NIC.
> >
> > Fixes: 00d7ddba1143 ("hv_netvsc: pair VF based on serial number")
> > Signed-off-by: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
> > ---
> >  drivers/net/hyperv/netvsc_drv.c | 15 +++++++++++----
> >  1 file changed, 11 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/net/hyperv/netvsc_drv.c
> > b/drivers/net/hyperv/netvsc_drv.c index 9bcaf204a7d4..8121ce34a39f
> > 100644
> > --- a/drivers/net/hyperv/netvsc_drv.c
> > +++ b/drivers/net/hyperv/netvsc_drv.c
> > @@ -2030,14 +2030,15 @@ static void netvsc_vf_setup(struct work_struct
> *w)
> >  	rtnl_unlock();
> >  }
> >
> > -/* Find netvsc by VMBus serial number.
> > - * The PCI hyperv controller records the serial number as the slot.
> > +/* Find netvsc by VF serial number.
> > + * The PCI hyperv controller records the serial number as the slot kobj name.
> >   */
> >  static struct net_device *get_netvsc_byslot(const struct net_device
> > *vf_netdev)  {
> >  	struct device *parent = vf_netdev->dev.parent;
> >  	struct net_device_context *ndev_ctx;
> >  	struct pci_dev *pdev;
> > +	u32 serial;
> >
> >  	if (!parent || !dev_is_pci(parent))
> >  		return NULL; /* not a PCI device */ @@ -2048,16 +2049,22
> @@ static
> > struct net_device *get_netvsc_byslot(const struct net_device *vf_netdev)
> >  		return NULL;
> >  	}
> >
> > +	if (kstrtou32(pdev->slot->kobj.name, 10, &serial)) {
> 
> kobject_name()?
> 
> And that feels _very_ fragile to me.  This is now an api that you are
> guaranteeing will never change?

Thanks for the suggestion -- I will update it to use kobject_name() to 
access the name.

For stability, the VF NIC's serial numbers are always unique according
to the Hyper-V documents. Other devices may have same numbers,
but they are not handled by netvsc driver.

Thanks,
- Haiyang