Re:Re:Re: [Xen-devel] some errors of pvonhvm : xen-blkfront

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Tue, 19 Apr 2011, topperxin wrote:
> hi Stefano
> ÂÂ thanks for your time
> ÂÂ As your method, I modified my /boo/grub/grub.cfg of ubuntu10.10 like this:
> ====================================================
> ÂÂÂmenuentry 'Ubuntu, with Linux 2.6.35.4.pvonhvm' --class ubuntu --class 
> gnu-linux --class gnu --class os {
> ÂÂ Â Â Ârecordfail
> ÂÂ Â Â Âinsmod part_msdos
> ÂÂ Â Â Âinsmod ext2
> ÂÂ Â Â Âset root='(hd0,msdos1)'
> ÂÂ Â Â Âsearch --no-floppy --fs-uuid --set 
> 3336889c-576e-4088-a6ff-89e869289766
>    Âlinux  /boot/vmlinuz-2.6.35.4 
> root=UUID=3336889c-576e-4088-a6ff-89e869289766 ro 
> xen_emul_unplug=aux-ide-disks
> ÂÂ Â Â Âinitrd Â/boot/initrd.img-2.6.35.4.pvonhvm.0415
> }
> =======================================================
> 
> then I reboot the Guest OS , I found the boot disk is still the xen-blkfront, 
> not the qemu emulate.

aux-ide-disks means "do not unplug secondary emulated disks".


> I reviewed the source of ./arch/x86/xen/platform-pci-unplug.c. there are 
> several parameters, such as:
> 
> ===================================================================
> ÂÂ Â Â Â Â Â Â Âif (!strncmp(p, "all", l))Â
> ÂÂ Â Â Â Â Â Â Â Â Â Â Âxen_emul_unplug |= XEN_UNPLUG_ALL;
> ÂÂ Â Â Â Â Â Â Âelse if (!strncmp(p, "ide-disks", l))Â
> ÂÂ Â Â Â Â Â Â Â Â Â Â Âxen_emul_unplug |= XEN_UNPLUG_ALL_IDE_DISKS;
> ÂÂ Â Â Â Â Â Â Âelse if (!strncmp(p, "aux-ide-disks", l))Â
> ÂÂ Â Â Â Â Â Â Â Â Â Â Âxen_emul_unplug |= XEN_UNPLUG_AUX_IDE_DISKS;
> ÂÂ Â Â Â Â Â Â Âelse if (!strncmp(p, "nics", l))Â
> ÂÂ Â Â Â Â Â Â Â Â Â Â Âxen_emul_unplug |= XEN_UNPLUG_ALL_NICS;
> ÂÂ Â Â Â Â Â Â Âelse if (!strncmp(p, "unnecessary", l))Â
> ÂÂ Â Â Â Â Â Â Â Â Â Â Âxen_emul_unplug |= XEN_UNPLUG_UNNECESSARY;
> ÂÂ Â Â Â Â Â Â Âelse if (!strncmp(p, "never", l))ÂÂÂ Â Â Â Â Â Â Â Â Â Â Â
> xen_emul_unplug |= XEN_UNPLUG_NEVER;
> =========================================================
> In my opinion , If I want to use the emulated disk , I should set
> 
> ÂÂ Â Â Â Â Â Âxen_emul_unplug = XEN_UNPLUG_UNNECESSARY or
> 
> ÂÂ Â Â Â Â Â Âxen_emul_unplug = XEN_NEVER
> 
> right? I try these two ways, but I still failed.

If you specify xen_emul_unplug=XEN_UNPLUG_UNNECESSARY you prevent
blkfront from hooking PV disks corresponding to emulated disks.
Of course you have to make sure your root device is not /dev/xvda
because that wouldn't work anymore, try root=/dev/sda if you want to
make sure that you are using the emulated path.
Also you need to specify hd* devices in your disk line in the VM config
file, like this:

disk = [ 'file:/root/images/debian_lenny_i386_small.raw,hda,w']


> 
> ÂÂCould you please tell me where can I get the source of
> 
> Âkernel 2.6.35 with pvonhvm???Â

The first Linux kernel to have PV on HVM support was Linux 2.6.36, so I
don't have any 2.6.35 Linux tree with PV on HVM support. However a
vanilla 2.6.36 (or 2.6.37 or 2.6.38) kernel should just work as PV on
HVM kernel.

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