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Bug 1320733

Summary:	[virt]hyperv should be enabled for all Windows OSes starting RHEV3.6
Product:	Red Hat Enterprise Virtualization Manager	Reporter:	Marina Kalinin <mkalinin>
Component:	ovirt-engine	Assignee:	Francesco Romani <fromani>
Status:	CLOSED ERRATA	QA Contact:	Nisim Simsolo <nsimsolo>
Severity:	high	Docs Contact:
Priority:	high
Version:	3.6.3	CC:	amarchuk, fromani, lsurette, mgoldboi, michal.skrivanek, nsimsolo, rbalakri, Rhev-m-bugs, srevivo, ykaul
Target Milestone:	ovirt-3.6.6	Keywords:	ZStream
Target Release:	3.6.6
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:	Cause: The system supports a range of HyperV-specific optimizations for windows operating systems guest. Those optimizations are not enabled by default. Consequence: Less than optimal performances for windows guest using default configuration; additional tuning required. Fix: Enable the HyperV optimizations by default. Result: Better out-of-the box experience for windows operating systems guests.	Story Points:	---
Clone Of:		Environment:
Last Closed:	2016-05-30 09:17:20 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	Virt	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	1320594
Bug Blocks:

Description Marina Kalinin 2016-03-23 21:22:07 UTC

Right now all HyperV enlightenment for Windows guests in RHEV are disabled. As of this bug#1163828.

RHEV 3.6 is based RHEL 7 hypervisors and bug#1063124 affects only RHEL 6, we should enable this flag by default and let Windows guests to enjoy the improvements brought by HyperV enlightments to kvm.

For RHEL6 - we can either disable this on vdsm side (to never enable hv_relaxed flag), or make this option configurable on the engine side.

Comment 1 Marina Kalinin 2016-03-23 21:25:03 UTC

Here is some more background on this:


We have absolutely different levels of supported "hv_" features in
rhel6.x and rhel7.x.

hv_relaxed is the only supported Hyper-V feature in rhel6.x. This flag
is a must for Win7/WS2008 on any RHEL version. Win8 and more recent
Windows versions can operate normally without this flag turned on. And
this is important, taking into account that on some CPU configurations
activating hv_relaxed flag can lead to the bug described in #1063124.

rhel7.x provides a better Hyper-V support, and seems to be free of the
problem mentioned in #1063124. In any case, disabling hv_relaxed for
Win8 and higher on rhel7.x should not affect the set other Hyper-V
optimizations (like spinlocks, vapic and reference time) supported by
KVM and explicitly enabled in QEMU command line.

Comment 9 Nisim Simsolo 2016-05-22 14:52:20 UTC

Verified: 
rhevm-3.6.6.2-0.1.el6
sanlock-3.2.4-2.el7_2.x86_64
libvirt-client-1.2.17-13.el7_2.4.x86_64
qemu-kvm-rhev-2.3.0-31.el7_2.11.x86_64
vdsm-4.17.28-0.el7ev.noarch

Comment 11 Michal Skrivanek 2016-05-30 09:17:20 UTC

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2016-1119.html