On Mon, Apr 29, 2013 at 08:01:52PM +0200, KONRAD Frédéric wrote:
> On 29/04/2013 19:52, Michael S. Tsirkin wrote:
> >On Mon, Apr 29, 2013 at 07:23:49PM +0200, KONRAD Frédéric wrote:
> >>On 29/04/2013 19:01, Michael S. Tsirkin wrote:
> >>
> >> On Mon, Apr 29, 2013 at 06:41:08PM +0200, KONRAD Frédéric wrote:
> >>
> >> On 29/04/2013 18:30, Michael S. Tsirkin wrote:
> >>
> >> On Mon, Apr 29, 2013 at 07:21:06PM +0300, Michael S. Tsirkin
> >> wrote:
> >>
> >> On Mon, Apr 29, 2013 at 06:14:41PM +0200, KONRAD Frédéric
> >> wrote:
> >>
> >> On 29/04/2013 18:02, Michael S. Tsirkin wrote:
> >>
> >> On Mon, Apr 29, 2013 at 10:55:36AM -0500, Jesse
> >> Larrew wrote:
> >>
> >> On 04/29/2013 10:29 AM, KONRAD Frédéric wrote:
> >>
> >> On 29/04/2013 17:14, Jesse Larrew wrote:
> >>
> >> On 04/29/2013 09:55 AM, KONRAD
> >> Frédéric 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 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
> >> <jlar...@linux.vnet.ibm.com>
> >> Signed-off-by: Jason Wang
> >> <jasow...@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.
> >>
> >>
> >> It seems to me that the real
> >> problem here is that host_features isn'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 =
> >> VIRTIO_DEVICE(qdev);
> >> VirtioDeviceClass *k =
> >> VIRTIO_DEVICE_GET_CLASS(qdev);
> >> assert(k->init != 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 the device
> >> is plugged into the bus using
> >> virtio_bus_plug_device().
> >>
> >> After talking with mdroth, I think
> >> the proper way to fix this would be to
> >> extend VirtioDeviceClass to
> >> include a calculate_config_size() method that
> >> can be called at the appropriate
> >> time during device initialization like so:
> >>
> >> static int
> >> virtio_device_init(DeviceState *qdev)
> >> {
> >> VirtIODevice *vdev =
> >> VIRTIO_DEVICE(qdev);
> >> VirtioDeviceClass *k =
> >> VIRTIO_DEVICE_GET_CLASS(qdev);
> >> assert(k->init != 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 before 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 triggered
> >> it yet. I'll confirm this afternoon.
> >>
> >> Ok, I think there is a problem with your
> >> patch:
> >>
> >> virtio_init(VIRTIO_DEVICE(n),
> >> "virtio-net", VIRTIO_ID_NET,
> >>
> >> n->config_size);
> >>
> >> is called in virtio_net_device_init
> >> (k->init).
> >>
> >> Is there a way to resize the config after
> >> that?
> >>
> >>
> >> Nope. That's definitely a bug. I can send a
> >> patch to fix this today. Any
> >> 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 != NULL) {
> >> klass->device_plugged(qbus->parent);
> >> }
> >>
> >> Seems the interesting part is in
> >> virtio_pci_device_plugged at the end:
> >>
> >> proxy->host_features |= 0x1 <<
> >> VIRTIO_F_NOTIFY_ON_EMPTY;
> >> proxy->host_features |= 0x1 <<
> >> VIRTIO_F_BAD_FEATURE;
> >> proxy->host_features =
> >> virtio_bus_get_vdev_features(bus,
> >> proxy->host_features);
> >>
> >> This is and was called after set_config_size, isn't
> >> that the issue?
> >>
> >> Basically devices expected everything to be setup at
> >> the point where init is called.
> >> We found one bug but let's fix it properly.
> >> There's no reason to delay parts of setup until after init,
> >> if we do, we'll trip on more uses of uninitialized data.
> >>
> >>
> >> 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
> >>
> >> Jesse Larrew
> >> Software Engineer, KVM Team
> >> IBM Linux Technology Center
> >> Phone: (512) 973-2052 (T/L: 363-2052)
> >> jlar...@linux.vnet.ibm.com
> >>
> >>
> >> --
> >>
> >> Jesse Larrew
> >> Software Engineer, KVM Team
> >> IBM Linux Technology Center
> >> Phone: (512) 973-2052 (T/L: 363-2052)
> >> jlar...@linux.vnet.ibm.com
> >>
> >> Basically this is what I propose. Warning! compile-tested
> >> only. (I also dropped an unused return value).
> >>
> >>
> >> Signed-off-by: Michael S. Tsirkin <m...@redhat.com>
> >>
> >> Which tree are you using? Is it up to date?
> >>
> >> Heh, more changes came in. So now, it's even simpler:
> >>
> >> Signed-off-by: Michael S. Tsirkin <m...@redhat.com>
> >>
> >> ---
> >>
> >> diff --git a/hw/virtio/virtio-bus.c b/hw/virtio/virtio-bus.c
> >> index aab72ff..447ba16 100644
> >> --- a/hw/virtio/virtio-bus.c
> >> +++ b/hw/virtio/virtio-bus.c
> >> @@ -38,7 +38,7 @@ do { printf("virtio_bus: " fmt , ## __VA_ARGS__); }
> >> while (0)
> >> #endif
> >>
> >> /* Plug the VirtIODevice */
> >> -int virtio_bus_plug_device(VirtIODevice *vdev)
> >> +void virtio_bus_plug_device(VirtIODevice *vdev)
> >> {
> >> DeviceState *qdev = DEVICE(vdev);
> >> BusState *qbus = BUS(qdev_get_parent_bus(qdev));
> >> @@ -51,8 +51,6 @@ int virtio_bus_plug_device(VirtIODevice *vdev)
> >> if (klass->device_plugged != NULL) {
> >> klass->device_plugged(qbus->parent);
> >> }
> >> -
> >> - return 0;
> >> }
> >>
> >> /* Reset the virtio_bus */
> >> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> >> index 0f88c25..c5228e6 100644
> >> --- a/hw/virtio/virtio.c
> >> +++ b/hw/virtio/virtio.c
> >> @@ -1091,11 +1091,11 @@ static int virtio_device_init(DeviceState
> >> *qdev)
> >> {
> >> VirtIODevice *vdev = VIRTIO_DEVICE(qdev);
> >> VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(qdev);
> >> + virtio_bus_plug_device(vdev);
> >> assert(k->init != NULL);
> >> if (k->init(vdev) < 0) {
> >> return -1;
> >> }
> >> - virtio_bus_plug_device(vdev);
> >> return 0;
> >> }
> >>
> >>
> >>Not sure this is what you want to do.
> >>The device would be plugged before it is inited :/.
> >I think this is exacly what we want to do.
> >In fact, this is what other buses do, because
> >devices simply can't init properly if they
> >do not know on which bus they reside.
> >
> >E.g. with pci:
> > do_pci_register_device (adds device on bus)
> > init
> >
> >We can add an analog of hotplug bus callback
> >if bus wants to get notified after device initialization.
> >I don't see a need for this though.
> >Do you?
> >
> >
> >
> No, as we don't want to allow virtio-device hotplug.
>
> but look at the plugged callback in virtio-pci:
>
> pci_set_word(config + PCI_SUBSYSTEM_ID, virtio_bus_get_vdev_id(bus));
>
> proxy->host_features = virtio_bus_get_vdev_features(bus,
> proxy->host_features);
>
> are impossible before the virtio-net init.
At this point I have to admit I don't understand what's
going on any more.
virtio_net_instance_init sets config size to
some value, then virtio_net_set_config_size overrides it...
Help!
I am guessing it's this hack that backfires somehow.
--
MST
