From: Thomas Falcon <tlfalcon@linux.ibm.com>
To: Nathan Lynch <nathanl@linux.ibm.com>
Cc: netdev@vger.kernel.org, tyreld@linux.ibm.com, msuchanek@suse.com,
linuxppc-dev@ozlabs.org
Subject: Re: [RFC PATCH] powerpc/pseries/mobility: notify network peers after migration
Date: Thu, 7 Nov 2019 15:30:58 -0600 [thread overview]
Message-ID: <83835ea7-e76b-35c1-88a8-e37dae5bb26e@linux.ibm.com> (raw)
In-Reply-To: <87lfss7ivo.fsf@linux.ibm.com>
On 11/6/19 4:14 PM, Nathan Lynch wrote:
> Hi Tom,
>
> Thomas Falcon <tlfalcon@linux.ibm.com> writes:
>> After a migration, it is necessary to send a gratuitous ARP
>> from all running interfaces so that the rest of the network
>> is aware of its new location. However, some supported network
>> devices are unaware that they have been migrated. To avoid network
>> interruptions and other unwanted behavior, force a GARP on all
>> valid, running interfaces as part of the post_mobility_fixup
>> routine.
> [...]
>
>> @@ -331,6 +334,8 @@ void post_mobility_fixup(void)
>> {
>> int rc;
>> int activate_fw_token;
>> + struct net_device *netdev;
>> + struct net *net;
>>
>> activate_fw_token = rtas_token("ibm,activate-firmware");
>> if (activate_fw_token == RTAS_UNKNOWN_SERVICE) {
>> @@ -371,6 +376,21 @@ void post_mobility_fixup(void)
>> /* Possibly switch to a new RFI flush type */
>> pseries_setup_rfi_flush();
>>
>> + /* need to force a gratuitous ARP on running interfaces */
>> + rtnl_lock();
>> + for_each_net(net) {
>> + for_each_netdev(net, netdev) {
>> + if (netif_device_present(netdev) &&
>> + netif_running(netdev) &&
>> + !(netdev->flags & (IFF_NOARP | IFF_LOOPBACK)))
>> + call_netdevice_notifiers(NETDEV_NOTIFY_PEERS,
>> + netdev);
>> + call_netdevice_notifiers(NETDEV_RESEND_IGMP,
>> + netdev);
>> + }
>> + }
>> + rtnl_unlock();
>> +
> This isn't an outright nak, but this is not nice. It illustrates the
> need to rethink the pseries partition migration code. There is no
> mechanism for drivers and other interested code to prepare for a
> migration or to adjust to the destination. So post_mobility_fixup() will
> continue to grow into a fragile collection of calls into unrelated
> subsystems until there is a better design -- either a pseries-specific
> notification/callback mechanism, or something based on the pm framework.
>
> My understanding is that this is needed specifically for ibmveth and,
> unlike ibmvnic, the platform does not provide any notification to that
> driver that a migration has occurred, right?
Correct, the ibmveth device, unlike ibmvnic, receives no signal or
notification at all in the event of a partition migration, so it can not
handle it or send a gratuitous ARP because from the driver's perspective
nothing has changed. As you've described, there is no existing notifier
in the kernel to inform interested parties that the system has migrated
or is about to migrate. Without adding the needed infrastructure to do
that, I'm not sure how else to fix this.
Tom
WARNING: multiple messages have this Message-ID (diff)
From: Thomas Falcon <tlfalcon@linux.ibm.com>
To: Nathan Lynch <nathanl@linux.ibm.com>
Cc: linuxppc-dev@ozlabs.org, netdev@vger.kernel.org,
msuchanek@suse.com, tyreld@linux.ibm.com
Subject: Re: [RFC PATCH] powerpc/pseries/mobility: notify network peers after migration
Date: Thu, 7 Nov 2019 15:30:58 -0600 [thread overview]
Message-ID: <83835ea7-e76b-35c1-88a8-e37dae5bb26e@linux.ibm.com> (raw)
In-Reply-To: <87lfss7ivo.fsf@linux.ibm.com>
On 11/6/19 4:14 PM, Nathan Lynch wrote:
> Hi Tom,
>
> Thomas Falcon <tlfalcon@linux.ibm.com> writes:
>> After a migration, it is necessary to send a gratuitous ARP
>> from all running interfaces so that the rest of the network
>> is aware of its new location. However, some supported network
>> devices are unaware that they have been migrated. To avoid network
>> interruptions and other unwanted behavior, force a GARP on all
>> valid, running interfaces as part of the post_mobility_fixup
>> routine.
> [...]
>
>> @@ -331,6 +334,8 @@ void post_mobility_fixup(void)
>> {
>> int rc;
>> int activate_fw_token;
>> + struct net_device *netdev;
>> + struct net *net;
>>
>> activate_fw_token = rtas_token("ibm,activate-firmware");
>> if (activate_fw_token == RTAS_UNKNOWN_SERVICE) {
>> @@ -371,6 +376,21 @@ void post_mobility_fixup(void)
>> /* Possibly switch to a new RFI flush type */
>> pseries_setup_rfi_flush();
>>
>> + /* need to force a gratuitous ARP on running interfaces */
>> + rtnl_lock();
>> + for_each_net(net) {
>> + for_each_netdev(net, netdev) {
>> + if (netif_device_present(netdev) &&
>> + netif_running(netdev) &&
>> + !(netdev->flags & (IFF_NOARP | IFF_LOOPBACK)))
>> + call_netdevice_notifiers(NETDEV_NOTIFY_PEERS,
>> + netdev);
>> + call_netdevice_notifiers(NETDEV_RESEND_IGMP,
>> + netdev);
>> + }
>> + }
>> + rtnl_unlock();
>> +
> This isn't an outright nak, but this is not nice. It illustrates the
> need to rethink the pseries partition migration code. There is no
> mechanism for drivers and other interested code to prepare for a
> migration or to adjust to the destination. So post_mobility_fixup() will
> continue to grow into a fragile collection of calls into unrelated
> subsystems until there is a better design -- either a pseries-specific
> notification/callback mechanism, or something based on the pm framework.
>
> My understanding is that this is needed specifically for ibmveth and,
> unlike ibmvnic, the platform does not provide any notification to that
> driver that a migration has occurred, right?
Correct, the ibmveth device, unlike ibmvnic, receives no signal or
notification at all in the event of a partition migration, so it can not
handle it or send a gratuitous ARP because from the driver's perspective
nothing has changed. As you've described, there is no existing notifier
in the kernel to inform interested parties that the system has migrated
or is about to migrate. Without adding the needed infrastructure to do
that, I'm not sure how else to fix this.
Tom
next prev parent reply other threads:[~2019-11-07 21:32 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-06 0:06 [RFC PATCH] powerpc/pseries/mobility: notify network peers after migration Thomas Falcon
2019-11-06 0:06 ` Thomas Falcon
2019-11-06 4:13 ` Russell Currey
2019-11-06 4:47 ` Thomas Falcon
2019-11-06 22:14 ` Nathan Lynch
2019-11-06 22:14 ` Nathan Lynch
2019-11-07 21:30 ` Thomas Falcon [this message]
2019-11-07 21:30 ` Thomas Falcon
2019-11-07 1:33 ` Michael Ellerman
2019-11-07 21:16 ` Thomas Falcon
2019-11-07 21:44 ` kbuild test robot
2019-11-08 16:56 ` kbuild test robot
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