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Converting Guest to PVM from HVM

user897654321 Newbie
Currently Being Moderated
I am trying to install the paravirtualized drivers, but not get the RPM to install properly.

The guest is OEL 5.5 and I do not think I have installed anything weird or unusual into the OS.

I do have Oracle RDBMS 10g Installed and running.

Here is the message I receive

[root@office Server]# rpm -ivh kernel-xen-2.6.18-194.el5.x86_64.rpm
Preparing... ########################################### [100%]
1:kernel-xen ########################################### [100%]
WARNING: No module xen_vbd found for kernel 2.6.18-194.el5xen, continuing anyway
[root@office Server]#

And when I try to mkinitd I am receiving a similar message about the xen_vbd.

Any ideas of what I need to install to get the module there?
  • 1. Re: Converting Guest to PVM from HVM
    499528 Pro
    Currently Being Moderated
    The xen pv drivers are already built into the pv kernel. When you install the pv kernel, mkinitrd tries to add all drivers used by the current kernel (hvm with pv drivers) into the initrd. Since the pv kernel doesn't have separate modules for these drivers, you get this warning. You can ignore it safely.
  • 2. Re: Converting Guest to PVM from HVM
    user897654321 Newbie
    Currently Being Moderated
    So if I simply ignore the error and then try the next step it fails:

    "From the 3.0 user's Guide
    3. Back up the old initrd file, and make the new one with xennet, xenblk driver:

    # mv initrd-oldversion.el5xen.img initrd-oldversion.el5xen.img.old
    # mkinitrd initrd-newversion.el5xen.img newversion.el5xen --with=xenblk --with=xennet --preload=xenblk --preload=xennet
    "


    I receive

    [root@office boot]# mkinitrd initrd-2.6.18-194.el5xen.img 2.6.18-194.el5xen with=xenblk with=xennet preload=xenblk preload=xennet
    No module xen_vbd found for kernel 2.6.18-194.el5xen, aborting.

    And the new .img file was not created.

    Seems like I need this xen_vbd.
  • 3. Re: Converting Guest to PVM from HVM
    499528 Pro
    Currently Being Moderated
    These are the instructions to convert HVM to PV-HVM, not to PVM. Which do you want?
  • 4. Re: Converting Guest to PVM from HVM
    user897654321 Newbie
    Currently Being Moderated
    I am trying to not use only HVM and simply want to go to PVM from there. The machine is currently labeled as HVM and I am trying to improve performance of it.

    For both I/O to the disks and for NIC speed.

    I assume changing the VM from HVM to PVM is not all I need to do.

    Following these instructions:


    8.11 Installing Paravirtualized Drivers

    For optimized performance, you can install paravirtualized drivers on hardware virtualized machines. Paravirtual drivers are optimized and improve the performance of the operating system in a virtual machine. These drivers enable high performance throughput of I/O operations in guest operating systems on top of the Oracle VM Server hosts.

    Creating hardware virtualized machines may require that you install paravirtual drivers for your hardware on the guest operating system.

    To install paravirtual drivers on an Oracle Linux guest operating system:

    Download the paravirtualized kernel on the virtual machine, for example for an Oracle Enterprise Linux 5.5 64-bit guest, download:

    http://public-yum.oracle.com/repo/EnterpriseLinux/EL5/5/base/x86_64/kernel-xen-2.6.18-194.el5.x86_64.rpm

    Install the paravirtualized kernel on the virtual machine:

    # rpm -ivh kernel-xen-version.type.rpm
    Preparing... ########################################### [100%]
    1:kernel-xen ########################################### [100%]
    Back up the old initrd file, and make the new one with xennet, xenblk driver:

    # mv initrd-oldversion.el5xen.img initrd-oldversion.el5xen.img.old
    # mkinitrd initrd-newversion.el5xen.img newversion.el5xen with=xenblk with=xennet preload=xenblk preload=xennet
    Edit the /boot/grub/grub.conf file to be:

    default=0
    timeout=5
    splashimage=(hd0,0)/grub/splash.xpm.gz
    hiddenmenu
    title Enterprise Linux Enterprise Linux Server (version.el5xen)
    root (hd0,0)
    kernel /vmlinuz-version.el5xen ro root=LABEL=/
    initrd /initrd-version.el5xen.img
    Modify the /etc/modprobe.conf file to include:

    alias scsi_hostadapter xenblk
    alias eth0 xennet
    Shut down the virtual machine. See Section 8.9.5, "Shutting Down a Virtual Machine" for information on shutting down a virtual machine.

    Edit the virtual machine and change the Domain Type to Xen PVM. See Section 8.9.9, "Editing a Virtual Machine" for information on editing a virtual machine.

    Start the virtual machine. See Section 8.9.1, "Starting a Virtual Machine" for information on starting a virtual machine.
  • 5. Re: Converting Guest to PVM from HVM
    861130 Newbie
    Currently Being Moderated
    HI,

    You can't convert from HVM to PVM - you just use PV drivers in a HVM machine. e.g. PV-HVM. That is what is confusing some people.

    HTH
  • 6. Re: Converting Guest to PVM from HVM
    499528 Pro
    Currently Being Moderated
    Note there are 3 modes for guests:
    HVM: unmodified kernel and drivers using software emulated devices
    PV-HVM: unmodified kernel with paravirtualized (Xen specific) disk and network drivers
    PV: modified kernel and drivers

    Those instructions are incorrect. Do not install the xen kernel if you just want to add PV drivers to your HVM guest.

    You can definitely convert an HVM guest to PV. This is documented in the Oracle VM 2.2 user's guide (section 4.7). The same procedure should still work for OVM 3.0.
  • 7. Re: Converting Guest to PVM from HVM
    user897654321 Newbie
    Currently Being Moderated
    So I should follow this Metalink Note?

    Oracle VM: Comparison of Guest Virtualisation Modes; HVM, PVM and PVHVM [ID 757719.1]

    and more importantly this section?

    "Configuration, Mode Validation and Conversion to PVHVM

    This section describes how to convert an exiting HVM guest to PVHVM mode. The use of latest package versions is strongly recommended before attempting conversion. Examples and excerpts provided can be used to validate and troubleshoot an existing PVHVM configuration."
  • 8. Re: Converting Guest to PVM from HVM
    499528 Pro
    Currently Being Moderated
    Which kernel are you currently running in that guest? And what output do you get from: lsmod|grep xen

    I suspect you may be running a kernel that already uses PV drivers, and their names are xen-vbd and xen-vnif.
  • 9. Re: Converting Guest to PVM from HVM
    user897654321 Newbie
    Currently Being Moderated
    [root@office Server]# uname -a
    Linux office.advantagedata.com 2.6.18-194.el5 #1 SMP Mon Mar 29 22:10:29 EDT 2010 x86_64 x86_64 x86_64 GNU/Linux



    [root@office Server]# lsmod |grep xen
    xen_vnif 58817 0 [permanent]
    xen_vbd 50345 0
    xen_balloon 45641 1 xen_vnif,[permanent]
    xen_platform_pci 117741 3 xen_vnif,xen_vbd,xen_balloon,[permanent]


    Its OEL 5.5 x86_64
  • 10. Re: Converting Guest to PVM from HVM
    499528 Pro
    Currently Being Moderated
    OK, that means you already have the PV drivers installed and running. To see which driver is used for your network interface, do:
    ls -l /sys/class/net/eth0/device/driver
    and for hda:
    ls -l /sys/block/hda/device/driver
  • 11. Re: Converting Guest to PVM from HVM
    user897654321 Newbie
    Currently Being Moderated
    # ls -l /sys/class/net/eth0/device/driver
    lrwxrwxrwx 1 root root 0 Oct 4 15:19 /sys/class/net/eth0/device/driver -> ../../../bus/pci/drivers/8139cp

    lrwxrwxrwx 1 root root 0 Oct 4 15:19 /sys/block/hda/device/driver -> ../../../../../bus/ide/drivers/ide-disk

    my current modprobe.conf only contains


    alias eth0 8139cp
    alias scsi_hostadapter ata_piix

    So it appears I am not using the xen drivers even though they are loaded in the kernel.. is that right?

    How to fix?
  • 12. Re: Converting Guest to PVM from HVM
    499528 Pro
    Currently Being Moderated
    1. fix modprobe.conf
    2. fix grub.conf
    3. fix vm.cfg
    4. reboot
  • 13. Re: Converting Guest to PVM from HVM
    user897654321 Newbie
    Currently Being Moderated
    Herbert van den Bergh wrote:
    1. fix modprobe.conf
    2. fix grub.conf
    3. fix vm.cfg
    4. reboot
    IN VM 3.0, I can not modify vm.cfg correct? So that would be an "Edit Virtual Machine" and change to PV

    On modprobe, I think I want to change


    alias eth0 8139cp
    alias scsi_hostadapter ata_piix

    to

    alias eth0 xen_vnif
    alias scsi_hostadapter xen_vbd


    Though I am not sure if its xen_vnif or xen-vnif or xennet
    and if it should be xen_vbd or xen-vbd or xenblk

    I have seen refereences to all of them.

    On grub.conf

    I currently have

    default=0
    timeout=5
    splashimage=(hd0,0)/grub/splash.xpm.gz
    hiddenmenu
    title Enterprise Linux (2.6.18-194.el5)
    root (hd0,0)
    kernel /vmlinuz-2.6.18-194.el5 ro root=/dev/VolGroup00/LogVol00 rhgb quiet
    initrd /initrd-2.6.18-194.el5.img

    and not sure what options I should add to the end of the kernel line.

    I don't need to run mkinitrd?
  • 14. Re: Converting Guest to PVM from HVM
    499528 Pro
    Currently Being Moderated
    user897654321 wrote:
    Herbert van den Bergh wrote:
    1. fix modprobe.conf
    2. fix grub.conf
    3. fix vm.cfg
    4. reboot
    IN VM 3.0, I can not modify vm.cfg correct? So that would be an "Edit Virtual Machine" and change to PV
    Change the virtual network controller and virtual disk to PV, not the VM itself. You are leaving it as HVM.

    >
    On modprobe, I think I want to change


    alias eth0 8139cp
    alias scsi_hostadapter ata_piix

    to

    alias eth0 xen_vnif
    alias scsi_hostadapter xen_vbd


    Though I am not sure if its xen_vnif or xen-vnif or xennet
    and if it should be xen_vbd or xen-vbd or xenblk

    I have seen refereences to all of them.
    xen-vbd and xen-vnif

    >
    On grub.conf

    I currently have

    default=0
    timeout=5
    splashimage=(hd0,0)/grub/splash.xpm.gz
    hiddenmenu
    title Enterprise Linux (2.6.18-194.el5)
    root (hd0,0)
    kernel /vmlinuz-2.6.18-194.el5 ro root=/dev/VolGroup00/LogVol00 rhgb quiet
    initrd /initrd-2.6.18-194.el5.img

    and not sure what options I should add to the end of the kernel line.
    hda=noprobe hdb=noprobe hdc=noprobe hdd=noprobe ide0=noprobe ide1=noprobe
    I don't need to run mkinitrd?
    Yes you do, but for your current kernel version, not the el5xen kernel.

    All this is in note 757719.1 as well, section 3.3 and onward.

    Edited by: Herbert van den Bergh on Oct 5, 2011 2:37 PM
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