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

[Bhushan Bharat-R65777]

> -----Original Message-----
> From: Alex Williamson [mailto:address@hidden
> Sent: Thursday, August 09, 2012 11:25 PM
> To: Bhushan Bharat-R65777
> Cc: Stuart Yoder; address@hidden; 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:address@hidden
> > > Sent: Thursday, August 09, 2012 8:28 PM
> > > To: Bhushan Bharat-R65777
> > > Cc: Alex Williamson; address@hidden; Avi Kivity
> > > Subject: Re: [Qemu-devel] Running KVM guest on X86
> > >
> > > On Tue, Aug 7, 2012 at 1:30 AM, Bhushan Bharat-R65777
> > > <address@hidden>
> > > wrote:
> > > >
> > > >
> > > >> -----Original Message-----
> > > >> From: Alex Williamson [mailto:address@hidden
> > > >> Sent: Monday, August 06, 2012 9:27 PM
> > > >> To: Bhushan Bharat-R65777
> > > >> Cc: address@hidden; 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?

Thanks
-Bharat

> 
> Alex
> 
> > [    1.307683] Pid: 1, comm: swapper/0 Not tainted 3.3.5-2.fc16.x86_64 #1
> > [    1.311201] Call Trace:
> > [    1.312548]  [<ffffffff815eac62>] panic+0xba/0x1cd
> > [    1.315160]  [<ffffffff81cf1075>] mount_block_root+0x258/0x283
> > [    1.318275]  [<ffffffff81cf10f3>] mount_root+0x53/0x57
> > [    1.321047]  [<ffffffff81cf1234>] prepare_namespace+0x13d/0x176
> > [    1.324206]  [<ffffffff81cf0d59>] kernel_init+0x156/0x15b
> > [    1.327114]  [<ffffffff81089587>] ? schedule_tail+0x27/0xb0
> > [    1.330102]  [<ffffffff815fd6a4>] kernel_thread_helper+0x4/0x10
> > [    1.333413]  [<ffffffff81cf0c03>] ? start_kernel+0x3c5/0x3c5
> > [    1.336446]  [<ffffffff815fd6a0>] ? gs_change+0x13/0x13
> >
> > Thanks
> > -Bharat
> >
> 
> 
>