Re: [Qemu-devel] [PATCH] virtio-net: count VIRTIO_NET_F_MAC when calculating config_len

[Jason Wang <jasowang@redhat.com>]

On 04/25/2013 03:06 PM, Michael S. Tsirkin wrote:
> On Thu, Apr 25, 2013 at 03:02:44PM +0800, Jason Wang wrote:
>> On 04/25/2013 02:59 PM, Michael S. Tsirkin wrote:
>>> On Thu, Apr 25, 2013 at 02:21:29PM +0800, Jason Wang wrote:
>>>> Commit 14f9b664 (hw/virtio-net.c: set config size using host features) tries to
>>>> calculate config size based on the host features. But it forgets the
>>>> VIRTIO_NET_F_MAC were always set for qemu later. This will lead a zero config
>>>> len for virtio-net device when both VIRTIO_NET_F_STATUS and VIRTIO_NET_F_MQ were
>>>> disabled form command line. Then qemu will crash when user tries to read the
>>>> config of virtio-net.
>>>>
>>>> Fix this by counting VIRTIO_NET_F_MAC and make sure the config at least contains
>>>> the mac address.
>>>>
>>>> Cc: Jesse Larrew <jlarrew@linux.vnet.ibm.com>
>>>> Signed-off-by: Jason Wang <jasowang@redhat.com>
>>>> ---
>>>>  hw/net/virtio-net.c |    3 ++-
>>>>  1 files changed, 2 insertions(+), 1 deletions(-)
>>>>
>>>> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
>>>> index 70c8fce..33a70ef 100644
>>>> --- a/hw/net/virtio-net.c
>>>> +++ b/hw/net/virtio-net.c
>>>> @@ -1264,7 +1264,8 @@ static void virtio_net_guest_notifier_mask(VirtIODevice *vdev, int idx,
>>>>  
>>>>  void virtio_net_set_config_size(VirtIONet *n, uint32_t host_features)
>>>>  {
>>>> -    int i, config_size = 0;
>>>> +    /* VIRTIO_NET_F_MAC can't be disabled from qemu side */
>>>> +    int i, config_size = feature_sizes[0].end;
>>> This would be cleaner:
>>> 	host_features |= (1 << VIRTIO_NET_F_MAC);
>>>
>>> no need for a comment then.
>> Sure, will send V2.
> Maybe ass assert(config_size) in core just to make sure
> other devices do not have this bug.

Prepare a patch for this, will send soon.
>>>>      for (i = 0; feature_sizes[i].flags != 0; i++) {
>>>>          if (host_features & feature_sizes[i].flags) {
>>>>              config_size = MAX(feature_sizes[i].end, config_size);
>>>> -- 
>>>> 1.7.1