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

[Pekka Enberg <penberg@kernel.org>]

On Wed, 10 Aug 2011, Asias He wrote:
> 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.

I reverted the patch for now. Thanks, Asias!