Re: [virtio-dev] [PATCH v4] content: Introduce VIRTIO_NET_F_STANDBY feature

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Sep 18, 2018 at 11:30:27AM -0700, Siwei Liu wrote:
> On Tue, Sep 18, 2018 at 6:25 AM, Michael S. Tsirkin <mst@redhat.com> wrote:
> > On Tue, Sep 18, 2018 at 01:37:35PM +0300, Sameeh Jubran wrote:
> >> On Tue, Sep 18, 2018 at 1:21 PM Cornelia Huck <cohuck@redhat.com> wrote:
> >> >
> >> > On Wed, 12 Sep 2018 11:22:12 -0400
> >> > "Michael S. Tsirkin" <mst@redhat.com> wrote:
> >> >
> >> > > On Wed, Sep 12, 2018 at 08:17:45AM -0700, Samudrala, Sridhar wrote:
> >> > > >
> >> > > >
> >> > > > On 9/7/2018 2:34 PM, Michael S. Tsirkin wrote:
> >> > > > > On Wed, Aug 15, 2018 at 11:49:15AM -0700, Sridhar Samudrala wrote:
> >> > > > > > VIRTIO_NET_F_STANDBY feature enables hypervisor to indicate virtio_net
> >> > > > > > device to act as a standby for another device with the same MAC address.
> >> > > > > >
> >> > > > > > Signed-off-by: Sridhar Samudrala <sridhar.samudrala@intel.com>
> >> > > > > > Acked-by: Cornelia Huck <cohuck@redhat.com>
> >> > > > > > Fixes: https://github.com/oasis-tcs/virtio-spec/issues/18
> >> > > > > Applied but when do you plan to add documentation as pointed
> >> > > > > out by Jan and Halil?
> >> > > >
> >> > > > I thought additional documentation will be done as part of the Qemu enablement
> >> > > > patches and i hope someone in RH is looking into it.
> >> > > >
> >> > > > Does it make sense to add a link to to the kernel documentation of this feature in
> >> > > > the spec
> >> > > >  https://www.kernel.org/doc/html/latest/networking/net_failover.html
> >> > >
> >> > >
> >> > > I do not think this will address the comments posted.  Specifically we
> >> > > should probably include documentation for what is a standby and primary:
> >> > > what is expected of driver (maintain configuration on standby, support
> >> > > primary coming and going, transmit on standby only if there is no
> >> > > primary) and of device (have same mac for standby as for standby).
> >> >
> >> > Yes, we need some definitive statements of what a driver and a device
> >> > is supposed to do in order to conform; it might make sense to discuss
> >> > this in conjunction with discussion on any QEMU patches (have not
> >> > checked whether anything has been posted, just returned from vacation).
> >> >
> >> > I assume that we still stick with the plan to implement/document
> >> > MAC-based handling first and then enhance with other methods later?
> >>
> >> I am currently in the process of writing the patches for this feature,
> >> I have thought about how the feature should be implemented
> >> and decided to go with a different approach. I've decided that the id
> >> of the vfio attached device will be specified in the virtio-net
> >> arguments as follows:
> >>
> >> -device virtio-net,standby=<device_id_of_vfio_device>
> >> -vfio #address,id=<device_id_of_vfio_device>
> >>
> >> This approach makes minimal changes to the current infrastructure and
> >> does so elegantly without adding unnecessary ids to the bridges.
> >>
> >> The mac address approach seems to be very complicated as there is no
> >> standard way to find the mac address of a given device and it is
> >> vendor dependent,
> >> which makes the task of identifying the target standby device by it's
> >> mac address a very tough one.
> >
> > Oh mac address is used by guest. I agree it's not a great qemu
> > interface.
> > The idea was basically to have -vfio #address,primary=<id>
> 
> Interesting... How do you make sure the MAC address are same (grouped)
> between vfio and virtio-net-pci (from QEMU side)? I thought the spec
> meant to make this a guest-host interface, right?
> 
> -Siwei

I guess at this point that can be up to the management tool.


> >
> >
> >> Please share your thoughts so I'll move forward with the patches.
> >
> > Can this actually support hotplug add and remove of the vfio device though?
> > E.g. hotplug add vfio device while VM is already running?
> > With the primary=<> it works because standby must always exist
> > even when primary isn't there.
> >
> >
> >> An initial patch which implements hiding the device from pci bus
> >> before the feature is acked is provided below:
> >>
> >> commit b716371bf4807fe16ffb4ffd901b69a110902a3c (HEAD -> failover)
> >> Author: Sameeh Jubran <sjubran@redhat.com>
> >> Date:   Sun Sep 16 13:21:41 2018 +0300
> >>
> >>     virtio-net: Implement standby feature
> >>
> >>     Signed-off-by: Sameeh Jubran <sjubran@redhat.com>
> >>
> >> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> >> index f154756e85..46386c0e1b 100644
> >> --- a/hw/net/virtio-net.c
> >> +++ b/hw/net/virtio-net.c
> >> @@ -26,7 +26,9 @@
> >>  #include "qapi/qapi-events-net.h"
> >>  #include "hw/virtio/virtio-access.h"
> >>  #include "migration/misc.h"
> >> +#include "hw/pci/pci.h"
> >>  #include "standard-headers/linux/ethtool.h"
> >> +#include "hw/vfio/vfio-common.h"
> >>
> >>  #define VIRTIO_NET_VM_VERSION    11
> >>
> >> @@ -1946,6 +1948,13 @@ void virtio_net_set_netclient_name(VirtIONet
> >> *n, const char *name,
> >>      n->netclient_type = g_strdup(type);
> >>  }
> >>
> >> +static bool standby_device_present(VirtIONet *n, const char *id,
> >> +        struct PCIDevice **pdev)
> >> +{
> >> +    return pci_qdev_find_device(id, pdev) >= 0 && pdev &&
> >> +    vfio_is_vfio_pci(*pdev);
> >> +}
> >> +
> >>  static void virtio_net_device_realize(DeviceState *dev, Error **errp)
> >>  {
> >>      VirtIODevice *vdev = VIRTIO_DEVICE(dev);
> >> @@ -1976,6 +1985,21 @@ static void
> >> virtio_net_device_realize(DeviceState *dev, Error **errp)
> >>          n->host_features |= (1ULL << VIRTIO_NET_F_SPEED_DUPLEX);
> >>      }
> >>
> >> +    if (n->net_conf.standby_id_str && standby_device_present(n,
> >> +                n->net_conf.standby_id_str, &n->standby_pdev)) {
> >> +        DeviceState *dev = DEVICE(n->standby_pdev);
> >> +        DeviceClass *klass = DEVICE_GET_CLASS(dev);
> >> +        /* Hide standby from pci till the feature is acked */
> >> +        if (klass->hotpluggable)
> >> +        {
> >> +            qdev_unplug(dev, errp);
> >
> >
> > Does this really hide the device?
> > I see:
> >     hdc = HOTPLUG_HANDLER_GET_CLASS(hotplug_ctrl);
> >     if (hdc->unplug_request) {
> >         hotplug_handler_unplug_request(hotplug_ctrl, dev, errp);
> >     } else {
> >         hotplug_handler_unplug(hotplug_ctrl, dev, errp);
> >     }
> >
> > which seems to just send an eject request to guest - the reverse of
> > what we want to do.
> >
> >> +            if (errp == NULL)
> >> +            {
> >> +                n->host_features |= (1ULL << VIRTIO_NET_F_STANDBY);
> >> +            }
> >
> > I'm not sure how is this error handling supposed to work.
> >
> >> +        }
> >> +    }
> >> +
> >>      virtio_net_set_config_size(n, n->host_features);
> >>      virtio_init(vdev, "virtio-net", VIRTIO_ID_NET, n->config_size);
> >>
> >> @@ -2198,6 +2222,7 @@ static Property virtio_net_properties[] = {
> >>                       true),
> >>      DEFINE_PROP_INT32("speed", VirtIONet, net_conf.speed, SPEED_UNKNOWN),
> >>      DEFINE_PROP_STRING("duplex", VirtIONet, net_conf.duplex_str),
> >> +    DEFINE_PROP_STRING("standby", VirtIONet, net_conf.standby_id_str),
> >>      DEFINE_PROP_END_OF_LIST(),
> >>  };
> >>
> >> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> >> index 866f0deeb7..593debe56e 100644
> >> --- a/hw/vfio/pci.c
> >> +++ b/hw/vfio/pci.c
> >> @@ -220,6 +220,12 @@ static void vfio_intx_disable_kvm(VFIOPCIDevice *vdev)
> >>  #endif
> >>  }
> >>
> >> +bool vfio_is_vfio_pci(PCIDevice* pdev)
> >> +{
> >> +    VFIOPCIDevice *vdev = DO_UPCAST(VFIOPCIDevice, pdev, pdev);
> >> +    return vdev->vbasedev.type == VFIO_DEVICE_TYPE_PCI;
> >> +}
> >> +
> >>  static void vfio_intx_update(PCIDevice *pdev)
> >>  {
> >>      VFIOPCIDevice *vdev = DO_UPCAST(VFIOPCIDevice, pdev, pdev);
> >> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
> >> index 821def0565..26dfde805f 100644
> >> --- a/include/hw/vfio/vfio-common.h
> >> +++ b/include/hw/vfio/vfio-common.h
> >> @@ -195,5 +195,6 @@ int vfio_spapr_create_window(VFIOContainer *container,
> >>                               hwaddr *pgsize);
> >>  int vfio_spapr_remove_window(VFIOContainer *container,
> >>                               hwaddr offset_within_address_space);
> >> +bool vfio_is_vfio_pci(PCIDevice* pdev);
> >>
> >>  #endif /* HW_VFIO_VFIO_COMMON_H */
> >> diff --git a/include/hw/virtio/virtio-net.h b/include/hw/virtio/virtio-net.h
> >> index 4d7f3c82ca..94388b40cb 100644
> >> --- a/include/hw/virtio/virtio-net.h
> >> +++ b/include/hw/virtio/virtio-net.h
> >> @@ -42,6 +42,7 @@ typedef struct virtio_net_conf
> >>      int32_t speed;
> >>      char *duplex_str;
> >>      uint8_t duplex;
> >> +    char *standby_id_str;
> >>  } virtio_net_conf;
> >>
> >>  /* Maximum packet size we can receive from tap device: header + 64k */
> >> @@ -103,6 +104,7 @@ typedef struct VirtIONet {
> >>      int announce_counter;
> >>      bool needs_vnet_hdr_swap;
> >>      bool mtu_bypass_backend;
> >> +    PCIDevice *standby_pdev;
> >>  } VirtIONet;
> >>
> >>  void virtio_net_set_netclient_name(VirtIONet *n, const char *name,
> >> (END)
> >>
> >> >
> >> > ---------------------------------------------------------------------
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> >> > For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org
> >> >
> >>
> >>
> >> --
> >> Respectfully,
> >> Sameeh Jubran
> >> Linkedin
> >> Software Engineer @ Daynix.
> >
> > ---------------------------------------------------------------------
> > To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org
> > For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org
> >

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