Re: [PATCH] kvm tools: Enable kernel DHCP autoconf by default

[Asias He <asias.hejun@gmail.com>]

On 08/10/2011 01:53 AM, Pekka Enberg wrote:
> As we boot to '/bin/sh' by default, enable kernel DHCP autoconfiguration too.
> The guest kernel needs to be configured with the following configuration
> options:
> 
>   CONFIG_IP_PNP=y
>   CONFIG_IP_PNP_DHCP=y
> 
> Cc: Asias He <asias.hejun@gmail.com>
> Cc: Avi Kivity <avi@redhat.com>
> Cc: Cyrill Gorcunov <gorcunov@gmail.com>
> Cc: Ingo Molnar <mingo@elte.hu>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: Prasad Joshi <prasadjoshi124@gmail.com>
> Cc: Sasha Levin <levinsasha928@gmail.com>
> Signed-off-by: Pekka Enberg <penberg@kernel.org>
> ---
>  tools/kvm/README        |    3 +++
>  tools/kvm/builtin-run.c |    2 +-
>  2 files changed, 4 insertions(+), 1 deletions(-)
> 
> diff --git a/tools/kvm/README b/tools/kvm/README
> index 5b85461..2cf9364 100644
> --- a/tools/kvm/README
> +++ b/tools/kvm/README
> @@ -70,6 +70,9 @@ linux-0.2.img.bz2
>   - For virtio-rng device (--rng):
>  	CONFIG_HW_RANDOM_VIRTIO=y
>  
> + - For kernel DHCP autoconf (when booting to /bin/sh):
> +	CONFIG_IP_PNP=y
> +	CONFIG_IP_PNP_DHCP=y
>  
>  5. And finally, launch the hypervisor:
>  
> diff --git a/tools/kvm/builtin-run.c b/tools/kvm/builtin-run.c
> index fa5de27..af7f59c 100644
> --- a/tools/kvm/builtin-run.c
> +++ b/tools/kvm/builtin-run.c
> @@ -601,7 +601,7 @@ int kvm_cmd_run(int argc, const char **argv, const char *prefix)
>  		using_rootfs = 1;
>  
>  		if (!strstr(real_cmdline, "init="))
> -			strlcat(real_cmdline, " init=/bin/sh ", sizeof(real_cmdline));
> +			strlcat(real_cmdline, " init=/bin/sh ip=dhcp ", sizeof(real_cmdline));
>  	}
>  
>  	if (!strstr(real_cmdline, "root="))

'ip=dhcp' makes kernel try to use nfs as root fs which results in a long
time 'wait and fail' and finally fallback to 9p as root fs.

[    1.688000] Sending DHCP requests ., OK
[    1.695000] IP-Config: Got DHCP answer from 192.168.33.1, my address
is 192.168.33.15
[    1.699000] IP-Config: Complete:
[    1.700000]      device=eth0, addr=192.168.33.15, mask=255.255.255.0,
gw=192.168.33.1,
[    1.703000]      host=192.168.33.15, domain=stu.buaa.edu.cn,
nis-domain=(none),
[    1.706000]      bootserver=192.168.33.1, rootserver=192.168.33.1,
rootpath=
[   36.769000] VFS: Unable to mount root fs via NFS, trying floppy.
[   36.771000] VFS: Mounted root (9p filesystem) on device 0:14.



-- 
Best Regards,
Asias He