[Qemu-discuss] Starting qemu with virtio and .raw file format

[Supriya Kher]

Hi,

I am using qemu-system_x86_64 to create a nested virtualization setup. The inner guest VM is
seen to be very slow. In order to improve guest VM performance I have been attempting to start external/outer VM using virtio option. However I encounter kernel crashes/failures each time.

 I start the outer VM running on Ubuntu using the following command line ( The VM image resides a disk file of .raw format)

 

# start qemu-kvm

  sudo $TOOLKIT_PATH/bin/qemu-system-x86_64 -nographic \

      -echr 20 \

      -cpu host \

      -m $MEMORY_SIZE \

      -smp $NUM_VCPUS \

      -drive file=$IMAGE_DISK,if=ide \

       $interfaces

 

Option 1:

 Changed if=ide to if=virtio

sudo $TOOLKIT_PATH/bin/qemu-system-x86_64 -nographic \

      -echr 20 \

      -cpu host \

      -m $MEMORY_SIZE \

      -smp $NUM_VCPUS \

      -drive file=$IMAGE_DISK,media=disk,if=virtio \

       $interfaces

 

VM crashed with the following trace:

md: ... autorun DONE.

Root-NFS: No NFS server available, giving up.

VFS: Unable to mount root fs via NFS, trying floppy.

VFS: Cannot open root device "sda6" or unknown-block(2,0)

Please append a correct "root=" boot option; here are the available partitions:

VFS: Unable to mount root fs on unknown-block(2,0)

User configuration error - no valid root filesystem found

Kernel panic - not syncing: Invalid configuration from end user prevents continuing

Pid: 1, comm: swapper Not tainted 2.6.34.10-grsec-WR4.3.0.0_cgl #1

Call Trace:

[<ffffffff817015d8>] ? gss_kerberos_ops+0xb9db8/0x1477e0

[<ffffffff817015d8>] ? gss_kerberos_ops+0xb9db8/0x1477e0

[<ffffffff815c1551>] panic+0xf5/0x16a

[<ffffffff8161cde0>] ? vga_con+0x0/0xd0

[<ffffffff818aa25b>] mount_block_root+0x1e3/0x1fa

[<ffffffff818aa33c>] mount_root+0xca/0xf6

[<ffffffff818aa4d8>] prepare_namespace+0x170/0x1a9

[<ffffffff818a9796>] kernel_init+0x21f/0x23b

[<ffffffff81003474>] kernel_thread_helper+0x4/0x10

[<ffffffff815c4d55>] ? restore_args+0x0/0x30

[<ffffffff818a9577>] ? kernel_init+0x0/0x23b

[<ffffffff81003470>] ? kernel_thread_helper+0x0/0x10

 

 

Option 2:

I next tried to append "root=  as indicated in the above error

sudo $TOOLKIT_PATH/bin/qemu-system-x86_64 -nographic \

      -echr 20 \

      -cpu host \

      -m $MEMORY_SIZE \

      -smp $NUM_VCPUS \

      -drive file=$IMAGE_DISK,media=disk,if=virtio \

      -append "root=/dev/sda1" \

       $interfaces

 

It appears that append option has to be accompanied with a corresponding "-kernel " option. VM Failed with error :

 

-append only allowed with -kernel option

 

Can someone help me in bringing up the VM using virtio the right way ?

Thanks
S. K