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Bug 1623690

Summary: RFE Please re-enable windows guest enlightenments disabled by #1336517
Product: Red Hat Enterprise Linux 7 Reporter: Mai Ling <mailinglists35>
Component: qemu-kvm-rhevAssignee: Vitaly Kuznetsov <vkuznets>
Status: CLOSED DUPLICATE QA Contact: FuXiangChun <xfu>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 7.6CC: ailan, areis, chayang, jen, jinzhao, jsuchane, juzhang, lijin, michen, virt-maint, vkuznets, xfu
Target Milestone: rcKeywords: FutureFeature, Regression
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: Doc Type: If docs needed, set a value
Doc Text:
Story Points: ---
Clone Of:
: 1628757 (view as bug list) Environment:
Last Closed: 2018-10-15 09:50:18 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 1631439    
Bug Blocks: 1624786    

Description Mai Ling 2018-08-29 21:53:02 UTC 
Description of problem:
idle windows 10 guests consume > 50%cpu

Version-Release number of selected component (if applicable):
http://cbs.centos.org/kojifiles/packages/qemu-kvm-ev/2.10.0/21.el7_5.4.1/src/qemu-kvm-ev-2.10.0-21.el7_5.4.1.src.rpm

How reproducible:
always

Steps to Reproduce:
1. run windows 1803 (or server 2019 insider) guest, uefi q35
2.
3.

Actual results:
idle guest takes >50% of host cpu

Expected results:
windows idle guest consumes 2-3% cpu (ideally zero like linux, but that's a different bug)

Additional info:
#1336517 disabled several hyper-v features.
the impact is windows 10 idle guests take big cpu cycles on host.
After learning from https://bugs.launchpad.net/qemu/+bug/1775702/comments/3 that I need hv-synic and hv-stimer, I've rebuilt locally qemu-kvm-ev-2.10.0-21.el7_5.4.1.src.rpm by reverting the "if 0" to "if 1" around these lines:

    DEFINE_PROP_BOOL("hv-synic", X86CPU, hyperv_synic, false),
    DEFINE_PROP_BOOL("hv-stimer", X86CPU, hyperv_stimer, false),

now guest cpu usage is down to 2-3% (needs kernel 4.2+ because ovmf secure boot needed by win10 images downloaded from ms ie modern.ie is supported only by kvm in kernel 4.2 or later)

please revert #1336517

thanks.