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 <[email protected]>
Cc: Avi Kivity <[email protected]>
Cc: Cyrill Gorcunov <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Prasad Joshi <[email protected]>
Cc: Sasha Levin <[email protected]>
Signed-off-by: Pekka Enberg <[email protected]>
---
 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!
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