From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:40274) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UWqXB-00068H-DX for qemu-devel@nongnu.org; Mon, 29 Apr 2013 12:02:39 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UWqX8-0000sI-7H for qemu-devel@nongnu.org; Mon, 29 Apr 2013 12:02:33 -0400 Received: from mx1.redhat.com ([209.132.183.28]:13893) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UWqX7-0000s8-UI for qemu-devel@nongnu.org; Mon, 29 Apr 2013 12:02:30 -0400 Date: Mon, 29 Apr 2013 19:02:13 +0300 From: "Michael S. Tsirkin" Message-ID: <20130429160213.GA10663@redhat.com> References: <1366870889-950-1-git-send-email-jasowang@redhat.com> <20130425065953.GB7299@redhat.com> <517E86BA.3020800@linux.vnet.ibm.com> <517E89E4.7050304@greensocs.com> <517E8E5A.5050202@linux.vnet.ibm.com> <517E91CD.9080602@greensocs.com> <517E97F8.5000803@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <517E97F8.5000803@linux.vnet.ibm.com> Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH] virtio-net: count VIRTIO_NET_F_MAC when calculating config_len List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jesse Larrew Cc: qemu-devel@nongnu.org, Jason Wang , aliguori@us.ibm.com, Michael Roth , KONRAD =?iso-8859-1?Q?Fr=E9d=E9ric?= On Mon, Apr 29, 2013 at 10:55:36AM -0500, Jesse Larrew wrote: > On 04/29/2013 10:29 AM, KONRAD Fr=E9d=E9ric wrote: > > On 29/04/2013 17:14, Jesse Larrew wrote: > >> On 04/29/2013 09:55 AM, KONRAD Fr=E9d=E9ric wrote: > >>> On 29/04/2013 16:42, Jesse Larrew wrote: > >>>> On 04/25/2013 01:59 AM, 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 fea= tures) 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 VIRT= IO_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 a= t least contains > >>>>>> the mac address. > >>>>>> > >>>>>> Cc: Jesse Larrew > >>>>>> Signed-off-by: Jason Wang > >>>>>> --- > >>>>>> 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 =3D 0; > >>>>>> + /* VIRTIO_NET_F_MAC can't be disabled from qemu side */ > >>>>>> + int i, config_size =3D feature_sizes[0].end; > >>>>> This would be cleaner: > >>>>> host_features |=3D (1 << VIRTIO_NET_F_MAC); > >>>>> > >>>>> no need for a comment then. > >>>>> > >>>> It seems to me that the real problem here is that host_features is= n't > >>>> properly populated before virtio_net_set_config_size() is called. = Looking > >>>> at virtio_device_init(), we can see why: > >>>> > >>>> static int virtio_device_init(DeviceState *qdev) > >>>> { > >>>> VirtIODevice *vdev =3D VIRTIO_DEVICE(qdev); > >>>> VirtioDeviceClass *k =3D VIRTIO_DEVICE_GET_CLASS(qdev); > >>>> assert(k->init !=3D NULL); > >>>> if (k->init(vdev) < 0) { > >>>> return -1; > >>>> } > >>>> virtio_bus_plug_device(vdev); > >>>> return 0; > >>>> } > >>>> > >>>> virtio_net_set_config_size() is currently being called as part of = the > >>>> k->init call, but the host_features aren't properly setup until th= e device > >>>> is plugged into the bus using virtio_bus_plug_device(). > >>>> > >>>> After talking with mdroth, I think the proper way to fix this woul= d be to > >>>> extend VirtioDeviceClass to include a calculate_config_size() meth= od that > >>>> can be called at the appropriate time during device initialization= like so: > >>>> > >>>> static int virtio_device_init(DeviceState *qdev) > >>>> { > >>>> VirtIODevice *vdev =3D VIRTIO_DEVICE(qdev); > >>>> VirtioDeviceClass *k =3D VIRTIO_DEVICE_GET_CLASS(qdev); > >>>> assert(k->init !=3D NULL); > >>>> if (k->init(vdev) < 0) { > >>>> return -1; > >>>> } > >>>> virtio_bus_plug_device(vdev); > >>>> + if (k->calculate_config_size && k->calculate_config_size(vdev)= < 0) { > >>>> + return -1; > >>>> + } > >>>> return 0; > >>>> } > >>>> > >>>> This would ensure that host_features contains the proper data befo= re any > >>>> devices try to make use of it to calculate the config size. > >>> Good point, I didn't saw that. > >>> > >>> but this was not the case with commit 14f9b664 no? > >>> > >> I suspect this bug was present in 14f9b664 as well. We just hadn't t= riggered > >> it yet. I'll confirm this afternoon. > >=20 > > Ok, I think there is a problem with your patch: > >=20 > > virtio_init(VIRTIO_DEVICE(n), "virtio-net", VIRTIO_ID_NET, > > n->config_size); > >=20 > > is called in virtio_net_device_init (k->init). > >=20 > > Is there a way to resize the config after that? > > >=20 > Nope. That's definitely a bug. I can send a patch to fix this today. An= y > objection to the method suggested above (extending VirtioDeviceClass)? This needs more thought. All devices expected everything is setup during the init call. config size is likely not the only issue. So we need almost all of virtio_bus_plug_device before init, and then after init send the signal: if (klass->device_plugged !=3D NULL) { klass->device_plugged(qbus->parent); } > >> > >>>>>> for (i =3D 0; feature_sizes[i].flags !=3D 0; i++) { > >>>>>> if (host_features & feature_sizes[i].flags) { > >>>>>> config_size =3D MAX(feature_sizes[i].end, config_= size); > >>>>>> --=20 > >>>>>> 1.7.1 > >> Jesse Larrew > >> Software Engineer, KVM Team > >> IBM Linux Technology Center > >> Phone: (512) 973-2052 (T/L: 363-2052) > >> jlarrew@linux.vnet.ibm.com > >> > >=20 >=20 >=20 > --=20 >=20 > Jesse Larrew > Software Engineer, KVM Team > IBM Linux Technology Center > Phone: (512) 973-2052 (T/L: 363-2052) > jlarrew@linux.vnet.ibm.com