[CentOS-virt] Megacli issue with Xen PERC 5/i Poweredge 2950 II

[Jeremy Martin]

I am having an issue with Megacli when adding or removing virtual 
disks.  I will post a link to fpaste that has the issue shown.

In brief whenever i add, or remove, a virtual disk via MegaCli the 
attempt succeeds and the adapter is configured but the OS remounts dm-0 
in read only.  dm-0 is my root lv.  This issue does not happen if i boot 
into the default, non Xen, CentOS kernel.  On stock CentOS kernel i can 
add and remove VD's all day without any issue at all. ONLY happens while 
booted up with the Xen kernel.

I have been racking my brain trying to figure this out.  Any help is 
appreciated.

My system:

Dell Poweredge 2950 II
PERC 5/i Controller

CentOS 6.7
Xen Version: 4.4.3-1.el6



*Fpaste showing the console log messages during the event:*

http://www.fpaste.org/277855/14445392/

*Full XL dump below:*

xl info
host                   : cmhinfra1.*
release                : 3.18.17-13.el6.x86_64
version                : #1 SMP Tue Jul 21 17:17:17 UTC 2015
machine                : x86_64
nr_cpus                : 8
max_cpu_id             : 7
nr_nodes               : 1
cores_per_socket       : 4
threads_per_core       : 1
cpu_mhz                : 1995
hw_caps                : 
bfebfbff:20100800:00000000:00000900:0004e33d:00000000:00000001:00000000
virt_caps              : hvm
total_memory           : 32762
free_memory            : 29340
sharing_freed_memory   : 0
sharing_used_memory    : 0
outstanding_claims     : 0
free_cpus              : 0
xen_major              : 4
xen_minor              : 4
xen_extra              : .3-1.el6
xen_version            : 4.4.3-1.el6
xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32 
hvm-3.0-x86_32p hvm-3.0-x86_64
xen_scheduler          : credit
xen_pagesize           : 4096
platform_params        : virt_start=0xffff800000000000
xen_changeset          : Thu Apr 23 15:06:13 2015 +0100 git:c5ec076-dirty
xen_commandline        : dom0_mem=1024M,max:1024M  loglvl=all 
guest_loglvl=all console=tty0 console=com2 com2=57600
cc_compiler            : gcc (GCC) 4.4.7 20120313 (Red Hat 4.4.7-16)
cc_compile_by          : mockbuild
cc_compile_domain      : centos.org
cc_compile_date        : Tue Sep  8 15:31:24 UTC 2015
xend_config_format     : 4


*grub.conf:*

jeremym]# cat /etc/grub.conf
# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making changes to this file
# NOTICE:  You have a /boot partition.  This means that
#          all kernel and initrd paths are relative to /boot/, eg.
#          root (hd0,0)
#          kernel /vmlinuz-version ro root=/dev/mapper/vg_cmhinfra1-lv_root
#          initrd /initrd-[generic-]version.img
#boot=/dev/sdb
default=0
timeout=5
#splashimage=(hd0,0)/grub/splash.xpm.gz
#hiddenmenu
serial --unit=1 --speed=57600
terminal --timeout console serial

title CentOS (3.18.17-13.el6.x86_64)
         root (hd0,0)
         kernel /xen.gz  dom0_mem=1024M,max:1024M  loglvl=all 
guest_loglvl=all console=tty0 console=com2 com2=57600
         module /vmlinuz-3.18.17-13.el6.x86_64 ro 
root=/dev/mapper/vg_cmhinfra1-lv_root rd_LVM_LV=vg_cmhinfra1/lv_swap 
rd_LVM_LV=vg_cmhinfra1/lv_root console=hvc0 nomodset
         module /initramfs-3.18.17-13.el6.x86_64.img
title CentOS (2.6.32-573.7.1.el6.x86_64)
         root (hd0,0)
         kernel /vmlinuz-2.6.32-573.7.1.el6.x86_64 ro 
root=/dev/mapper/vg_cmhinfra1-lv_root rd_NO_LUKS  KEYBOARDTYPE=pc 
KEYTABLE=us LANG=en_US.UTF-8 rd_NO_MD rd_LVM_LV=vg_cmhinfra1/lv_swap 
SYSFONT=latarcyrheb-sun16 crashkernel=auto 
rd_LVM_LV=vg_cmhinfra1/lv_root rd_NO_DM rhgb quiet console=ttyS1,57600 
console=tty0

         initrd /initramfs-2.6.32-573.7.1.el6.x86_64.img
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