Re: [Qemu-devel] Running KVM guest on X86

[Alex Williamson <alex.williamson@redhat.com>]

On Thu, 2012-08-09 at 18:06 +0000, Bhushan Bharat-R65777 wrote:
> 
> > -----Original Message-----
> > From: Alex Williamson [mailto:alex.williamson@redhat.com]
> > Sent: Thursday, August 09, 2012 11:25 PM
> > To: Bhushan Bharat-R65777
> > Cc: Stuart Yoder; qemu-devel@nongnu.org; Avi Kivity
> > Subject: Re: [Qemu-devel] Running KVM guest on X86
> > 
> > On Thu, 2012-08-09 at 17:39 +0000, Bhushan Bharat-R65777 wrote:
> > >
> > > > -----Original Message-----
> > > > From: Stuart Yoder [mailto:b08248@gmail.com]
> > > > Sent: Thursday, August 09, 2012 8:28 PM
> > > > To: Bhushan Bharat-R65777
> > > > Cc: Alex Williamson; qemu-devel@nongnu.org; Avi Kivity
> > > > Subject: Re: [Qemu-devel] Running KVM guest on X86
> > > >
> > > > On Tue, Aug 7, 2012 at 1:30 AM, Bhushan Bharat-R65777
> > > > <R65777@freescale.com>
> > > > wrote:
> > > > >
> > > > >
> > > > >> -----Original Message-----
> > > > >> From: Alex Williamson [mailto:alex.williamson@redhat.com]
> > > > >> Sent: Monday, August 06, 2012 9:27 PM
> > > > >> To: Bhushan Bharat-R65777
> > > > >> Cc: qemu-devel@nongnu.org; Avi Kivity
> > > > >> Subject: Re: Running KVM guest on X86
> > > > >>
> > > > >> On Mon, 2012-08-06 at 15:40 +0000, Bhushan Bharat-R65777 wrote:
> > > > >> > Hi Avi/All,
> > > > >> >
> > > > >> > I am facing issue to boot KVM guest on x86 (I used to work on
> > > > >> > PowerPC platform
> > > > >> and do not have enough knowledge of x86). I am working on making
> > > > >> VFIO working on PowerPC Booke, So I have cloned Alex Williamsons
> > > > >> git repository, compiled kernel for x86 on fedora with
> > > > >> virtualization configuration (selected all kernel config options
> > > > >> for same). Run below command to boot Guest (I have not provided vfio
> > device yet):
> > > > >> >
> > > > >> > "qemu-system-x86_64 -enable-kvm -m 1024 -nographic -kernel
> > > > >> arch/x86_64/boot/bzImage -initrd /boot/initramfs-3.5.0-rc4+.img
> > > > >> -serial tcp::4444,server,telnet"
> > > > >> >
> > > > >> > After the I can see qemu command line (able to run various
> > > > >> > commands like "info
> > > > >> registers" etc), while guest does not boot (not even the first print
> > comes).
> > > > >> >
> > > > >> > Can anyone help in what I am missing or doing wrong?
> > > > >>
> > > > >> x86 doesn't use the serial port for console by default, so you're
> > > > >> making things quite a bit more difficult that way.  Typically
> > > > >> you'll want to provide a disk image (the -hda option is the
> > > > >> easiest way to do this), a display (-vga std -vnc :0 is again
> > > > >> easiest), and probably something to install from (-cdrom
> > > > >> <image.iso>).  You can also add a -boot d to get it to choose the cdrom
> > the first time for install.
> > > > >> Thanks,
> > > > >
> > > > > Thanks Avi and Alex, I can see the KVM guest boot prints by adding
> > > > > -append
> > > > "console=ttyS0"
> > > >
> > > > Note, once you get to user space you will need a getty specified in
> > > > inittab in order to get a login on your serial port.   Something like:
> > > >
> > > >    T0:23:respawn:/sbin/getty -L ttyS0
> > >
> > > 1)
> > > I tried booting with prebuilt qcow2 then it works for me:
> > > qemu-system-x86_64  -enable-kvm  -nographic  -device sga  -m 1024 -hda
> > > debian_squeeze_amd64_standard.qcow2
> > >
> > > Does anyone help on how I can add my kernel to qcow2? Or create a proper
> > qcow2?
> > >
> > > 2)
> > > Also I tried as mentioned in section "3.9 Direct Linux Boot":
> > http://qemu.weilnetz.de/qemu-doc.html#disk_005fimages :
> > >
> > > qemu-kvm  -enable-kvm  -nographic -kernel /boot/vmlinuz-3.5.0+ -hda
> > > /boot/initramfs-3.5.0+.img  -append "console=ttyS0 root=/dev/sda" -m
> > > 1024
> > >
> > > I get below error :
> > > [    1.299225] No filesystem could mount root, tried:  ext3 ext2 ext4 iso9660
> > > [    1.303232] Kernel panic - not syncing: VFS: Unable to mount root fs on
> > unknown-block(8,0)
> > 
> > 
> > Chances are your root is a partition on /dev/sda, not the disk itself (ex. sda1,
> > sda2)... Why exactly are you causing yourself so much pain by doing these direct
> > boot, no VGA options instead of starting with an ISO image, installing it, then
> > setting up a serial console if you want serial access?  This may be the norm for
> > powerpc VMs, but it's not how I think most people setup x86 VMs.  Thanks,
> 
> I have a fedora machine to which I do not have direct access (but I can reboot remotely, have a console). So far what I was trying direct booting VM using same initramfs and bzimage as of host,
> 
> Alex, How I can create a ISO image with my kernel? Where I should place that on host?

No, what I'm suggesting is to get an ISO image of the distribution you
want to run on the guest and use the -cdrom <iso image> -boot d options
to boot the VM from the ISO and install onto your disk image.  If you
want to make the process even easier, use something like virt-manager to
install the guest, then use the disk image directly with qemu if you
want.  Thanks,

Alex