Re: [Xen-devel] booting from HVM (?pv?)

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Tue, Jun 25, 2013 at 07:32:42PM +0200, AL13N wrote:
> Op dinsdag 25 juni 2013 20:25:16 schreef Pasi Kärkkäinen:
> > On Tue, Jun 25, 2013 at 07:21:48PM +0200, AL13N wrote:
> > > Op dinsdag 25 juni 2013 18:39:06 schreef Pasi Kärkkäinen:
> > > > On Mon, Jun 24, 2013 at 10:21:48PM +0200, AL13N wrote:
> > > > > Hi,
> > > > > 
> > > > > I'm the Mageia XEN packager and during QA, we stumbled into a problem.
> > > > > 
> > > > > in fact, we wanted to test Mageia 3 installation on a HVM.
> > > > > 
> > > > > so, we had a sparse image and a iso file:
> > > > > 
> > > > > [ 'file:/opt/testhvm.img,sda,w',
> > > > > 'file:/opt/mageialive.iso,hdb:cdrom,r' ]
> > > > > 
> > > > > the live booted, and was able to install to disk, but it never seemed
> > > > > to
> > > > > boot after the install... (for some reason)
> > > > > 
> > > > > in the end, this "worked" when we changed to:
> > > > > 
> > > > > [ 'file:/opt/testhvm.img,xvda,w', 'file:/opt/testhvm.img,sda,w' ]
> > > > > 
> > > > > apparently 'xvda' to get grub to boot the kernel; and 'sda' so that it
> > > > > could start...
> > > > > 
> > > > > 
> > > > > any idea as to why it can't be booted with sda? is there a specific
> > > > > driver
> > > > > missing?
> > > > 
> > > > See here for more info:
> > > > http://wiki.xen.org/wiki/Xen_Linux_PV_on_HVM_drivers
> > > > 
> > > > This config works for both HVM and PVHVM:
> > > > disk = [ 'phy:/dev/vg01/f16pvhvm-disk0,hda,w',
> > > > 'file:/root/iso/Fedora-16-x86_64-DVD.iso,hdc:cdrom,r' ]
> > > > 
> > > > You can enable or disable PV drivers with:
> > > > xen_platform_pci=0|1
> > > 
> > > i'm assuming that hda (ide_generic) would be using regular emulation? and
> > > the pv driver (xenblk_front) could be hda, sda, or xvda and it will
> > > choose the one you've chosen in the config? (via xen_platform_pci)?
> > 
> > Yeah, if xen_platform_pci=0 then hda will be emulated, and if
> > xen_platform_pci=1 then xen-blkfront will start and "unplug" the emulated
> > hda, so there's only xvda.
> 
> the pv drivers don't use hda and sda anymore? only xvda?
>

yes, the Linux Xen PV drivers (xen-blkfront) only exposes xvd* devices.

You can easily verify that with booting Linux HVM guest with xen_platform_pci= 
and xen_platform_pci=1 and comparing the block devices visible inside the VM.

-- Pasi


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