Bug 725876

Summary:	RTC interrupt problems with RHEL5 qemu/kvm (0.10 based) on 2.6.38+ guest kernels.
Product:	Red Hat Enterprise Linux 5	Reporter:	john stultz <johnstul>
Component:	kvm	Assignee:	Gleb Natapov <gleb>
Status:	CLOSED ERRATA	QA Contact:	Virtualization Bugs <virt-bugs>
Severity:	high	Docs Contact:
Priority:	unspecified
Version:	5.7	CC:	juzhang, knoel, mkenneth, rhod, shuang, uobergfe, virt-maint, xfu
Target Milestone:	rc
Target Release:	---
Hardware:	x86_64
OS:	Linux
Whiteboard:
Fixed In Version:	kvm-83-243.el5	Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2012-02-21 03:15:07 UTC	Type:	---
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:
Bug Blocks:	580949

Description john stultz 2011-07-26 20:21:25 UTC

Description of problem:

The RHEL5 qemu/kvm (0.10 based) does not properly emulate RTC Alarm (AIE) interrupts. Newer kernels (2.6.38+) use AIE interrupts exclusively for RTC functionality (including UIE mode).

This manifests in issues like the following, when running recent guest kernels on a RHEL5 kvm host system.

[root@hwclock ~]# hwclock 
select() to /dev/rtc to wait for clock tick timed out

Proper AIE mode emulation was added to qemu/kvm in 0.11.

While it is non-trivial, I think backporting the AIE support to the RHEL5 qemu/kvm package would be the best solution here.


Version-Release number of selected component (if applicable):
KVM version: 0.10.50

How reproducible:
Always when using 2.6.38+ kernels.


Steps to Reproduce:
1. Boot 2.6.38+ kernel with RHEL5 kvm
2. Run hwclock (or any other application that accesses the rtc with AIE or UIE mode irqs)
  
Actual results:
No interrupts when in UIE or AIE mode, causing applications to fail.

Expected results:
UIE and AIE mode interrupts should function, and applications would run normally.

Additional info:
This issue was originally reported here:
https://bugzilla.kernel.org/show_bug.cgi?id=36252

Comment 3 Suqin Huang 2011-08-16 07:33:59 UTC

can reproduce it with fedora guest, so add qe_ack +

1). #hwclock
select() to /dev/rtc to wait for clock tick timed out

2). guest
2.6.38.6-26.rc1.fc15.x86_64

3). kvm: kvm-83-239.el5

Comment 4 Ulrich Obergfell 2011-10-11 07:57:29 UTC

We are considering a back-port of qemu upstream commit

   f292787d9addffd5f0a2df9516c158bfb5792b61

to address the RTC Alarm Interrupt issue. Additionally,
we are considering a back-port of qemu upstream commit

   98815437f731372d9456f6a2ad103f3b836a9646

The two combined patches should make rtc_update_second2()
similar to RHEL6 code.

Comment 20 FuXiangChun 2011-12-12 11:06:29 UTC

1.reproduce with kmod-kvm-83-239.el5 and 2.6.38.6-26.rc1.fc15.x86_64

steps to reproduce

1.1. install fedora15 guest
1.2.boot guest
/usr/libexec/qemu-kvm  -M rhel5.6.0 -m 4096 -smp 4,cores=2,threads=1,sockets=2 -cpu qemu64,vendor="AuthenticAMD",+sse2 -soundhw all -name win7 -usbdevice tablet -rtc-td-hack -uuid 123465d2-2032-848d-bda0-de7adb149048 -boot nc -drive file=/home/fedora/fedora15.qcow2,if=virtio,boot=on,bus=0,unit=0,format=qcow2,cache=none,boot=on,werror=stop -net nic,macaddr=54:52:00:27:12:23,vlan=0,model=virtio -soundhw ac97 -net tap,vlan=0,script=/etc/qemu-ifup -serial pty -parallel none -usb -balloon none -monitor stdio -spice host=0,ic=on,port=5911,disable-ticketing -qxl 1

1.3.# hwclock

actual result: 
select() to /dev/rtc to wait for clock tick timed out

2.verify with kvm-83-246.el5 and 2.6.38.6-26.rc1.fc15.x86_64

2.1.repeat 1.1
2.2.repeat 1.2
2.3 repeat 1.3

actual result:
# hwclock 
Mon 12 Dec 2011 06:02:06 AM EST  -0.184707 seconds

base on above testing result, this bug is fixed.

Comment 22 errata-xmlrpc 2012-02-21 03:15:07 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.

http://rhn.redhat.com/errata/RHSA-2012-0149.html