On Fri, 9 Dec 2016 20:09:49 +0000 Haiyang Zhang <haiyangz@xxxxxxxxxxxxx> wrote: > > -----Original Message----- > > From: Stephen Hemminger [mailto:stephen@xxxxxxxxxxxxxxxxxx] > > Sent: Friday, December 9, 2016 1:21 PM > > To: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> > > Cc: KY Srinivasan <kys@xxxxxxxxxxxxx>; olaf@xxxxxxxxx; Haiyang Zhang > > <haiyangz@xxxxxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; > > bjorn.helgaas@xxxxxxxxx; apw@xxxxxxxxxxxxx; devel@xxxxxxxxxxxxxxxxxxxxxx; > > leann.ogasawara@xxxxxxxxxxxxx; jasowang@xxxxxxxxxx > > Subject: Re: [PATCH 3/3] hv_netvsc: Implement VF matching based on > > serial numbers > > > > On Fri, 9 Dec 2016 08:31:22 +0100 > > Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > > > > On Fri, Dec 09, 2016 at 12:05:53AM +0000, KY Srinivasan wrote: > > > > > > > > > > > > > -----Original Message----- > > > > > From: Greg KH [mailto:gregkh@xxxxxxxxxxxxxxxxxxx] > > > > > Sent: Thursday, December 8, 2016 7:56 AM > > > > > To: KY Srinivasan <kys@xxxxxxxxxxxxx> > > > > > Cc: linux-kernel@xxxxxxxxxxxxxxx; devel@xxxxxxxxxxxxxxxxxxxxxx; > > > > > olaf@xxxxxxxxx; apw@xxxxxxxxxxxxx; vkuznets@xxxxxxxxxx; > > > > > jasowang@xxxxxxxxxx; leann.ogasawara@xxxxxxxxxxxxx; > > > > > bjorn.helgaas@xxxxxxxxx; Haiyang Zhang <haiyangz@xxxxxxxxxxxxx> > > > > > Subject: Re: [PATCH 3/3] hv_netvsc: Implement VF matching based on > > serial > > > > > numbers > > > > > > > > > > On Thu, Dec 08, 2016 at 12:33:43AM -0800, > > kys@xxxxxxxxxxxxxxxxxxxxxx > > > > > wrote: > > > > > > From: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx> > > > > > > > > > > > > We currently use MAC address to match VF and synthetic NICs. > > Hyper-V > > > > > > provides a serial number to both devices for this purpose. This > > patch > > > > > > implements the matching based on VF serial numbers. This is the > > way > > > > > > specified by the protocol and more reliable. > > > > > > > > > > > > Signed-off-by: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx> > > > > > > Signed-off-by: K. Y. Srinivasan <kys@xxxxxxxxxxxxx> > > > > > > --- > > > > > > drivers/net/hyperv/netvsc_drv.c | 55 > > > > > ++++++++++++++++++++++++++++++++++++--- > > > > > > 1 files changed, 51 insertions(+), 4 deletions(-) > > > > > > > > > > > > diff --git a/drivers/net/hyperv/netvsc_drv.c > > > > > b/drivers/net/hyperv/netvsc_drv.c > > > > > > index 9522763..c5778cf 100644 > > > > > > --- a/drivers/net/hyperv/netvsc_drv.c > > > > > > +++ b/drivers/net/hyperv/netvsc_drv.c > > > > > > @@ -1165,9 +1165,10 @@ static void netvsc_free_netdev(struct > > > > > net_device *netdev) > > > > > > free_netdev(netdev); > > > > > > } > > > > > > > > > > > > -static struct net_device *get_netvsc_bymac(const u8 *mac) > > > > > > +static struct net_device *get_netvsc_byvfser(u32 vfser) > > > > > > { > > > > > > struct net_device *dev; > > > > > > + struct net_device_context *ndev_ctx; > > > > > > > > > > > > ASSERT_RTNL(); > > > > > > > > > > > > @@ -1175,7 +1176,8 @@ static void netvsc_free_netdev(struct > > net_device > > > > > *netdev) > > > > > > if (dev->netdev_ops != &device_ops) > > > > > > continue; /* not a netvsc device */ > > > > > > > > > > > > - if (ether_addr_equal(mac, dev->perm_addr)) > > > > > > + ndev_ctx = netdev_priv(dev); > > > > > > + if (ndev_ctx->vf_serial == vfser) > > > > > > return dev; > > > > > > } > > > > > > > > > > > > @@ -1205,21 +1207,66 @@ static void netvsc_free_netdev(struct > > > > > net_device *netdev) > > > > > > return NULL; > > > > > > } > > > > > > > > > > > > +static u32 netvsc_get_vfser(struct net_device *vf_netdev) > > > > > > +{ > > > > > > + struct device *dev; > > > > > > + struct hv_device *hdev; > > > > > > + struct hv_pcibus_device *hbus = NULL; > > > > > > + struct list_head *iter; > > > > > > + struct hv_pci_dev *hpdev; > > > > > > + unsigned long flags; > > > > > > + u32 vfser = 0; > > > > > > + u32 count = 0; > > > > > > + > > > > > > + for (dev = &vf_netdev->dev; dev; dev = dev->parent) { > > > > > > > > > > You are going to walk the whole device tree backwards? That's > > crazy. > > > > > And foolish. And racy and broken (what happens if the tree > > changes > > > > > while you do this?) Where is the lock being grabbed while this > > happens? > > > > > What about reference counts? Do you see other drivers ever doing > > this > > > > > (if you do, point them out and I'll go yell at them too...) > > > > > > > > Greg, > > > > > > > > We are registering for netdev events. Coming into this function, the > > caller > > > > guarantees that the list of netdevs does not change - we assert this > > on entry: > > > > ASSERT_RTNL(). We are only walking up the device tree for the > > netdevs whose > > > > state change is being notified to us - the device tree being walked > > here is limited to > > > > netdevs under question. > > > > > > But a netdev is a child of some type of "real" device, and you are now > > > walking the tree of all devices up to the "root" parent device, which > > > means you will hit PCI bridges, USB controllers, and all sorts of fun > > > things if you are a child of those types of devices. > > > > > > And can't you tell if the netdev for this event, really is "your" > > > netdev? Or are you getting called this for "all" netdevs? Sorry, I > > > don't know this api, any pointers to it would be appreciated. > > > > > > > We have a reference to the device and we know the device is not > > going away. Is it not > > > > safe to dereference the parent pointer - after all the child has > > taken a reference on > > > > the parent as part of device_add() call. > > > > > > It might be, and might not be. There's a reason you don't see this > > > pattern anywhere in the kernel because of this... > > > > > > > > > + if (!dev_is_vmbus(dev)) > > > > > > + continue; > > > > > > > > > > Ick. > > > > > > > > > > Why isn't your parent pointer a vmbus device all the time? How > > could > > > > > you get burried down in the device hierarchy when you are the > > driver for > > > > > a specific bus type in the first place? How could this function > > ever be > > > > > called for a device that is NOT of this type? > > > > > > > > We get notified when state changes on any of the netdev devices in > > the system. > > > > Not all netdevs in the system belong to vmbus. Consider for instance > > the > > > > emulated NIC that can be configured. This is an emulated PCI NIC. We > > are only > > > > interested in netdevs that correspond to the VF instance that we are > > interested in. > > > > > > Can you "know" this is your netdev by some other way than having to > > walk > > > the device tree? Name? local device type? Something else? This > > seems > > > like an odd api in that everyone would have to do gyrations like this > > in > > > order to determine if the netdev is "theirs" or not... > > > > The scenario is SR-IOV on Hyper-V. In the case of VF device, the host > > hands the > > guest OS a PCI device for the virtual function device. The VF device is > > placed > > on a special synthetic PCI bus (ie not part of the other buses on the > > system). > > The VF device also has a synthetic network interface (netvsc) which > > lives > > on VMBUS. This code is about managing the interaction between the two. > > > > The association between VF and synthetic NIC is done in response to the > > VF network device being registered. Initial version was based on MAC > > address > > which is the same. Later refinement used permanent MAC address to > > avoid bugs if MAC address changed. This version is to use serial number > > instead which is safer than MAC address. > > > > The code to walk up/down maybe not be needed to find serial number. > > Perhaps a more direct single set of conditions is possible? > > > > Something like: > > > > In pci-hyperv.c > > > > u32 hv_pcifront_get_serial(struct pci_bus *bus, unsigned int devfn) > > { > > struct hv_pcibus_device *hbus > > = container_of(bus->sysdata, > > struct hv_pcibus_device, sysdata); > > struct hf_pci_dev *hpdev; > > u32 serial; > > > > hpdev = get_pcichild_wslot(hbus, devfn_to_wslot(pdev->devfn)); > > if (!hpdev) > > return 0; > > > > serial = hpdev->devs.ser; > > put_pcichild(hpdev, hv_pcidev_ref_by_slot); > > return serial; > > } > > > > In netvsc_drv.c > > > > static u32 netvsc_get_vfser(struct net_device *vf_netdev) > > { > > struct device *dev = vf_netdev->dev.parent; > > struct pci_dev *pdev; > > u32 wslot; > > > > if (!dev || !dev_is_pci(dev)) > > return 0; > > > > pdev = container_of(dev, struct pci_device, dev); > > > > return hv_pcifront_get_serial(pdev->bus, pdev->devfn); > > } > > > > > > > > > > > > P.S: it would be good to be able to get win_slot out through sysfs as > > well for systemd/udev. > > Stephen, > > Thanks for suggestion. Actually, in my earlier implementation of this > feature (VF serial based matching), I thought about export a function > from vPCI driver, then calling it from netvsc. So I don't need to > move structs between headers... But, it creates a dependency of netvsc > on vPCI driver's symbol. So, even if on a VM without SRIOV, we have to > load vPCI driver, which we don't want. > > Also, hv_vpci device is 3 parent layers above the vf_netdevice: > Here is the VF drv hierarchy -- > Should we assume it's always 3 parents above vf_netdevice, or search for it? > > [ 368.185259] HZINFO:NETDEV_REGISTER: > [ 368.185261] HZINFO: dev:ffff88007c10d518, bus: (null), busName:(null), drvName:(null) > [ 368.185262] HZINFO: dev:ffff88007c10c0a0, bus:ffffffff81ce4b60, busName:pci, drvName:ixgbevf > [ 368.185263] HZINFO: dev:ffff8800355c0000, bus: (null), busName:(null), drvName:(null) > [ 368.185264] HZINFO: dev:ffff8800355c5428, bus:ffffffffa0008160, busName:vmbus, drvName:hv_pci > [ 368.185264] HZINFO: dev:ffff88007c49e268, bus:ffffffff81ce9800, busName:acpi, drvName:vmbus > [ 368.185265] HZINFO: dev:ffff88007c48ea68, bus:ffffffff81ce9800, busName:acpi, drvName:(null) > [ 368.185266] HZINFO: dev:ffff88007c48aa68, bus:ffffffff81ce9800, busName:acpi, drvName:(null) > [ 368.185266] HZINFO: dev:ffff88007c48a268, bus:ffffffff81ce9800, busName:acpi, drvName:(null) > [ 368.185267] HZINFO: dev:ffff88007c489a68, bus:ffffffff81ce9800, busName:acpi, drvName:(null) > > Thanks, > - Haiyang Since this is a synthetic bus, the topology should not change unless host side software changes. The vf_netdev device has to be PCI device, so that is going to be certain. After that there maybe intermediate up to hv_pci. The code in hyperv-pci already has similar stuff (ie for read_config). _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
