Bug 463455 - [LTC 6.0 FEAT] 200785:Improved handling of dynamic subchannel mapping
[LTC 6.0 FEAT] 200785:Improved handling of dynamic subchannel mapping
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: kernel (Show other bugs)
s390x All
high Severity high
: alpha
: 6.0
Assigned To: Hans-Joachim Picht
Martin Jenner
: FutureFeature
Depends On:
Blocks: 356741
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Reported: 2008-09-23 11:21 EDT by IBM Bug Proxy
Modified: 2010-07-02 03:03 EDT (History)
3 users (show)

See Also:
Fixed In Version:
Doc Type: Enhancement
Doc Text:
Story Points: ---
Clone Of:
Last Closed: 2009-09-22 17:05:25 EDT
Type: ---
Regression: ---
Mount Type: ---
Documentation: ---
Verified Versions:
Category: ---
oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

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Description IBM Bug Proxy 2008-09-23 11:21:11 EDT
=Comment: #0=================================================
Emily J. Ratliff <emilyr@us.ibm.com> - 2008-09-16 17:35 EDT
1. Feature Overview:
Feature Id:	[200785]
a. Name of Feature:	Improved handling of dynamic subchannel mapping
b. Feature Description
This item has its root in zVM not having persistent subchannels for devices (that means, a device
may first appear on subchannel x and after detach and attach, on subchannel y). This triggers a
limitation in the driver model: a device (the ccw_device) cannot be moved from one parent device
(subchannel x) to another  parent device (subchannel y) without unregistering/reregistering, which
defeats keeping the devices in a special state to keep the block devices. This means a  device will
stay in disconnected state and not reappear, even if it is available  from zVM.

2. Feature Details:
Sponsor:	zSeries

Arch Specificity: Both
Affects Core Kernel: Yes
Delivery Mechanism: Direct from community
Category:	Kernel
Request Type:	Kernel - Enhancement from IBM
d. Upstream Acceptance:	Accepted
Sponsor Priority	1
f. Severity: High
IBM Confidential:	no
Code Contribution:	IBM code
g. Component Version Target:	2.6.20

3. Business Case
Improved managebility & reliability.  Certain z/VM management action can lead to errors in Linux w/o
this feature.

4. Primary contact at Red Hat: 
John Jarvis

5. Primary contacts at Partner:
Project Management Contact:
Hans-Georg Markgraf, mgrf@de.ibm.com, Boeblingen 49-7031-16-3978

Technical contact(s):
Gonzalo Muelas Serrano, gmuelas@de.ibm.com

IBM Manager:
Thomas Schwarz, t.schwarz@de.ibm.com
Comment 1 Bill Nottingham 2008-10-02 13:48:43 EDT
RHEL 6 will include a newer kernel than 2.6.20, so this should not be an issue.

The feature requested has already been accepted into the upstream code base
planned for the next major release of Red Hat Enterprise Linux.

When the next milestone release of Red Hat Enterprise Linux 6 is available,
please verify that the feature requested is present and functioning as
Comment 2 Hans-Joachim Picht 2009-09-22 17:05:25 EDT
Code is included in the rhel6 kernel via upstream. Marked as
CLOSED/CURRENTRELEASE by Hans-Joachim Picht <hpicht@redhat.com>
Comment 3 IBM Bug Proxy 2010-07-02 03:03:29 EDT
------- Comment From mgrf@de.ibm.com 2010-07-02 02:52 EDT-------
This feature is verified on R6 snapshots
Set feature to "verified"  Thx

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