Re: [RFT/PATCH v2] kvm tools: Add read-only support for block devices

[Ingo Molnar <mingo@elte.hu>]

* Pekka Enberg <penberg@kernel.org> wrote:

> Add support for booting guests to host block devices in read-only mode.
> 
> Cc: Asias He <asias.hejun@gmail.com>
> Cc: Cyrill Gorcunov <gorcunov@gmail.com>
> Cc: Prasad Joshi <prasadjoshi124@gmail.com>
> Cc: Sasha Levin <levinsasha928@gmail.com>
> Cc: Ingo Molnar <mingo@elte.hu>
> Signed-off-by: Pekka Enberg <penberg@kernel.org>
> ---
>  tools/kvm/disk-image.c |   39 +++++++++++++++++++++++++++++++--------
>  1 files changed, 31 insertions(+), 8 deletions(-)

Nice patch - booting into the host's userspace works out of box now. The 
following disk-image-less command:

   ./kvm run ../../arch/x86/boot/bzImage --readonly --image=/dev/sda --params="root=/dev/vda1"

has booted all the way into the host's Fedora Rawhide userspace:

   ===================================
   Welcome to Fedora release 16 (Rawhide)!

   [...]

   Fedora release 16 (Rawhide)
   Kernel 2.6.39-rc3-tip+ on an x86_64 (ttyS0)

   aldebaran login: 
   ===================================

I ran this as unprivileged user (who had read access to the partitions in 
question).

This is a very useful feature for testing kernels - i can test any random Linux 
box's userspace via KVM, without having to copy an image there! :-)

Tested-by: Ingo Molnar <mingo@elte.hu>

Thanks,

	Ingo