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== Comment: #26 - Guilherme Guaglianoni Piccoli <gpicc...@br.ibm.com> - 
2016-07-15 16:26:38 ==
When performing hotplug operations in PowerPC currently, if we remove a PHB and 
re-add it later, its domain address is incremented. An example below (drmgr is 
the tool we use in PowerPC to perform this operation):


(i) $>  lspci
0000:60:00.0 Ethernet controller: Broadcom Corporation NetXtreme II BCM57810 10 
Gigabit Ethernet
0000:60:00.1 Ethernet controller: Broadcom Corporation NetXtreme II BCM57810 10 
Gigabit Ethernet

(ii) $>  drmgr -c phb -s "PHB 20" -r  # removing a PHB

(iii) $>  lspci #empty

(iv) $>  drmgr -c phb -s "PHB 20" -a  # re-adding the PHB

(v) $>  lspci
0001:60:00.0 Ethernet controller: Broadcom Corporation NetXtreme II BCM57810 10 
Gigabit Ethernet
0001:60:00.1 Ethernet controller: Broadcom Corporation NetXtreme II BCM57810 10 
Gigabit Ethernet


This behavior is harmful when kernel is using network predictable naming for 
interfaces, for example, since after the PHB re-add, the PCI address of NIC 
functions changes, and so the interfaces' naming also change. Recently, a patch 
was merged to powerpc-next to avoid this situation, by relating the PCI domain 
number with device-tree properties. With the patch, the above steps (i) and (v) 
present the same output for lspci.

We want to ask Canonical to merge the patch in Ubuntu Xenial's kernel,
since it will solve multiple bugs we've experienced by performing NIC
hotplug - the commit is present on powerpc-next under the commit-id
63a72284b15.

A link to the patch:
https://git.kernel.org/cgit/linux/kernel/git/powerpc/linux.git/commit/?id=63a72284b159c569ec52f380c9

Thanks in advance,


Guilherme

** Affects: linux (Ubuntu)
     Importance: Undecided
     Assignee: Taco Screen team (taco-screen-team)
         Status: New


** Tags: architecture-ppc64le bugnameltc-136437 severity-high 
targetmilestone-inin16041
-- 
Hotplug remove and re-add adds PCI adapter to next PCI domain (PCI)
https://bugs.launchpad.net/bugs/1603574
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