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Bug 1283079

Summary:	qemu process exit after hot-plug a memory device which guest use 1G hugepages
Product:	Red Hat Enterprise Linux 7	Reporter:	Jan Kurik <jkurik>
Component:	qemu-kvm-rhev	Assignee:	Igor Mammedov <imammedo>
Status:	CLOSED ERRATA	QA Contact:	Virtualization Bugs <virt-bugs>
Severity:	medium	Docs Contact:
Priority:	high
Version:	7.2	CC:	dyuan, hhuang, honzhang, huding, imammedo, jen, jherrman, juzhang, knoel, lhuang, mrezanin, pkrempa, rbalakri, sherold, virt-maint, xfu, yuhuang
Target Milestone:	rc	Keywords:	ZStream
Target Release:	---
Hardware:	x86_64
OS:	Linux
Whiteboard:
Fixed In Version:	qemu-kvm-rhev-2.3.0-31.el7_2.2	Doc Type:	Bug Fix
Doc Text:	Due to an unhandled error, the qemu-kvm process exited when trying to hot-plug memory devices on guests using 1GB hugepages. With this update, the error is handled within qemu-kvm, and as a result, the process does not crash.	Story Points:	---
Clone Of:	1270144	Environment:
Last Closed:	2015-12-07 21:43:47 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:	1270144
Bug Blocks:

Description Jan Kurik 2015-11-18 07:58:52 UTC

This bug has been copied from bug #1270144 and has been proposed
to be backported to 7.2 z-stream (EUS).

Comment 3 Yumei Huang 2015-11-19 09:08:32 UTC

Reproduce:
kernel:  3.10.0-329.el7.x86_64
qemu-kvm: qemu-kvm-rhev-2.3.0-31.el7.x86_64

steps:
1. prepare hugepages env:
#cat /proc/cmdline 
BOOT_IMAGE=/vmlinuz-3.10.0-329.el7.x86_64 root=/dev/mapper/rhel_dhcp--10--61-root ro console=tty0 console=ttyS0,115200 reboot=pci crashkernel=auto rd.lvm.lv=rhel_dhcp-10-61/root rd.lvm.lv=rhel_dhcp-10-61/swap biosdevname=0 rhgb intel_iommu=on default_hugepagesz=1G hugepagesz=1G hugepages=4 hugepagesz=2M hugepages=0

#mount
...
hugetlbfs on /dev/hugepages1G type hugetlbfs (rw,relatime,pagesize=1G)
...

# cat /proc/meminfo | grep Huge
AnonHugePages:     24576 kB
HugePages_Total:       8
HugePages_Free:        8
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:    1048576 kB

2. start a guest with 1G hugepage:
/usr/libexec/qemu-kvm -name rhel72-sn5 -m 4G,slots=8,maxmem=40G -mem-prealloc -mem-path /dev/hugepages1G -numa node  \ 
-realtime mlock=on  \
 -smp 16,sockets=16,cores=1,threads=1 \
-no-user-config -nodefaults -rtc base=utc,driftfix=slew -global kvm-pit.lost_tick_policy=discard -boot menu=on,strict=on \
-object iothread,id=iothread0 -drive file=/home/guest/rhel72-sn5.img,if=none,id=drive-data-disk,format=qcow2,cache=none,aio=native,werror=stop,rerror=stop  -device virtio-blk-pci,drive=drive-data-disk,id=data-disk,iothread=iothread0,bus=pci.0,addr=0x7 \
-netdev tap,id=hostnet1,vhost=on -device e1000,netdev=hostnet1,id=net2,mac=10:1a:4a:42:0a:0b,bus=pci.0,addr=0xa \
-usb -device usb-tablet,id=input0 -vga qxl \
-spice port=5901,addr=0.0.0.0,disable-ticketing,image-compression=off,seamless-migration=on -monitor stdio  \
-msg timestamp=on

3. hotplug a memory device with size=512M
(qemu) object_add memory-backend-file,id=mem0,size=512M,mem-path=/dev/hugepages1G
2015-11-13T07:41:46.486441Z memory size 0x20000000 must be equal to or larger than huge page size 0x40000000
And the qemu process exit.

So, the bug is reproduced.

Verify:
kernel: 3.10.0-331.el7.x86_64
qemu-kvm: qemu-kvm-rhev-2.3.0-31.el7_2.2

With same steps as above. The guest doesn't quit, and HMP prints "memory size 0x20000000 must be equal to or larger than huge page size 0x40000000".

So, the bug is fixed.

Comment 4 Yumei Huang 2015-11-23 07:30:37 UTC

Reverify:
kernel: 3.10.0-327.3.1.el7.x86_64
qemu-kvm: qemu-kvm-rhev-2.3.0-31.el7_2.3

QE retest on above environment as same steps as comment 3, The guest doesn't quit, and HMP prints "memory size 0x20000000 must be equal to or larger than huge page size 0x40000000".
So the bug is fixed.

Comment 9 errata-xmlrpc 2015-12-07 21:43:47 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-2015-2555.html