Bug 694515

Summary:	[6.2 FEAT] Dynamic QEMU parameter change to separate block cache setting from write cache enable
Product:	Red Hat Enterprise Linux 6	Reporter:	IBM Bug Proxy <bugproxy>
Component:	qemu-kvm	Assignee:	Brian Stein <bstein>
Status:	CLOSED WONTFIX	QA Contact:	Virtualization Bugs <virt-bugs>
Severity:	medium	Docs Contact:
Priority:	medium
Version:	6.4	CC:	amit.shah, bstevens, jjarvis, juzhang, mkenneth, nobody+PNT0273897, sbest, sglass, tburke, virt-maint
Target Milestone:	beta	Keywords:	FutureFeature, OtherQA
Target Release:	6.4
Hardware:	x86_64
OS:	All
Whiteboard:
Fixed In Version:		Doc Type:	Enhancement
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2012-05-17 19:06:31 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Bug Depends On:
Bug Blocks:	745944, 746047

Description IBM Bug Proxy 2011-04-07 14:32:32 UTC

1. Feature Overview:
Feature Id: [71086]
a. Name of Feature: [6.2 FEAT] Dynamic QEMU parameter change
b. Feature Description
QEMU has a number of parameters that can be specified at invocation time or are default. At this
time, restarting QEMU with the changed parameter values is the only way, if one needs to switch the
parameter=value tuple. Whereas dynamically changing some of these parameters is possible, the
infrastructure to do that needs to be put in place.

We are currently collating all such parameters that are candidates for dynamic change at run-time
and building infrastructure, with necessary underlying changes to handle the switch. This is a long
term effort and we'd like all such parameters that have made it upstream at the time of a distro
cut, to make it into the distro update.

Note, that the current upstream work by Christoph is needed, but consider the feature request
complete, we need to ensure that there is a monitor command (available via libvirt's pass-through)
to direct this change without requiring a guest visible change.

2. Feature Details:
Sponsor: LTC RAS
Architectures: x86, x86_64,
Arch Specificity: purely common code
Affects Kernel Modules: No
Delivery Mechanism: Direct from Community
Category: other
Request Type: Toolchain - Enhancement from Upstream
d. Upstream Acceptance: In Progress
Sponsor Priority P3
f. Severity: normal
IBM Confidential: No
Code Contribution: IBM code
g. Component Version Target: ---

3. Business Case
QEMU is a foundation layer for much of the Linux KVM virtualization stack. With virtualization and
cloud infrastructures becoming ubiquitous, simple parameter changes should not result in service
downtime, requiring restart of VMs, if they can be handled at runtime. This feature helps both in
availability of VMs as well as going a long way in SLA adherance.

4. Primary contact at Red Hat:
John Jarvis, jjarvis

5. Primary contacts at Partner:
Project Management Contact:
Michael W. Wortman, wortman.com

Technical contact(s):
Ananth Narayan M G, ananth.narayan.com

Comment 2 RHEL Program Management 2011-04-07 14:44:06 UTC

Since RHEL 6.1 External Beta has begun, and this bug remains
unresolved, it has been rejected as it is not proposed as
exception or blocker.

Red Hat invites you to ask your support representative to
propose this request, if appropriate and relevant, in the
next release of Red Hat Enterprise Linux.

Comment 3 John Jarvis 2011-04-11 16:25:30 UTC

IBM is signed up to test and provide feedback, setting OtherQA.

Comment 4 IBM Bug Proxy 2011-05-25 15:10:29 UTC

------- Comment From wortman.com 2011-05-25 11:08 EDT-------
Deferring to RHEL 6.3

Comment 5 John Jarvis 2011-05-25 15:22:00 UTC

Reflagging and moving to the 6.3 trackers.

Comment 8 IBM Bug Proxy 2011-09-02 16:40:49 UTC

------- Comment From mcintire.com 2011-09-02 12:31 EDT-------
IBM is deferring from 6.3 to a future release.

Comment 9 IBM Bug Proxy 2011-10-18 14:12:01 UTC

------- Comment From mcintire.com 2011-10-18 10:03 EDT-------
IBM is requesting this in 6.3.   We believe we can get the required function accepted upstream by 12/23.  Sorry for the mixed messages on this.

Comment 10 John Jarvis 2011-10-18 14:18:30 UTC

Understood, this is currently on the 6.3 tracker.

Comment 11 IBM Bug Proxy 2011-10-18 14:21:36 UTC

------- Comment From mcintire.com 2011-10-18 10:11 EDT-------
Dynamic QEMU parameter change will be done in 3 phases:

Phase 1 - for 6.3
Get dynamic hostcache change code along with framework for safely reopen images for 'raw' block drivers (raw, raw-posix and raw-win32) implemented.

PHase 2 and 3 later release
Phase 2:
Enhance the framework developed in Phase 1 to other 'important' block drivers.
Phase 3:
Implement dynamic change of other parameters to completely replace cache=xx in qemu.

Phase 1 is the solution GTS cloud team is looking for based on which this feature was raised.

Comment 12 IBM Bug Proxy 2011-11-17 22:10:32 UTC

------- Comment From mcintire.com 2011-11-17 17:06 EDT-------
Red Hat, we are moving this request to 6.4

Comment 13 John Jarvis 2011-11-18 04:32:40 UTC

Reflagged and moved to the RHEL 6.4 tracker.

Comment 15 IBM Bug Proxy 2012-04-18 21:50:25 UTC

------- Comment From mcintire.com 2012-04-18 21:45 EDT-------
Red Hat - IBM is dropping this feature request.