>
> On Wed, Jun 27, 2018 at 04:55:20PM +0530, Pankaj Gupta wrote:
> > virtio-rng device causing old guest kernels(2.6.32) to hang on latest
> > qemu.
> > The driver attempts to read from the virtio-rng device too early in it's
> > initialization. Qemu detects guest is not ready and returns, resulting in
> > hang.
>
> Presumably this all worked previously at some point, so do you know what
> change in QEMU has caused a regression in this regard.
Latest qemu(2.x) has this issue with older guest kernel(2.6.32) versions.
But it does work properly with upstream guest kernel because the way virtio-rng
driver is reworked, it sends request to virtio-rng driver when(before) there is
read call.
If guest driver is ready when it notifies qemu this works fine. There are number
of changes in guest virtio/driver code infrastructure as well as qemu side, I
don't
know exact commit after which this stopped working for older guest kernels.
Thanks,
Pankaj
>
> >
> > Fix is to handle pending request when guest is running and driver status
> > is
> > set to 'VIRTIO_CONFIG_S_DRIVER_OK'.
> >
> > Reported-by: Sergio lopez <slope...@redhat.com>
> > Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
> > Signed-off-by: Pankaj Gupta <pagu...@redhat.com>
> > ---
> > v1->v2: Update new status value early only for virtio-rng (Stefan)
> >
> > hw/virtio/virtio-rng.c | 14 ++++++++++++++
> > 1 file changed, 14 insertions(+)
> >
> > diff --git a/hw/virtio/virtio-rng.c b/hw/virtio/virtio-rng.c
> > index 289bbcac03..855f1b41d1 100644
> > --- a/hw/virtio/virtio-rng.c
> > +++ b/hw/virtio/virtio-rng.c
> > @@ -156,6 +156,19 @@ static void check_rate_limit(void *opaque)
> > vrng->activate_timer = true;
> > }
> >
> > +static void virtio_rng_set_status(VirtIODevice *vdev, uint8_t status)
> > +{
> > + VirtIORNG *vrng = VIRTIO_RNG(vdev);
> > +
> > + if (!vdev->vm_running) {
> > + return;
> > + }
> > + vdev->status = status;
> > +
> > + /* Something changed, try to process buffers */
> > + virtio_rng_process(vrng);
> > +}
> > +
> > static void virtio_rng_device_realize(DeviceState *dev, Error **errp)
> > {
> > VirtIODevice *vdev = VIRTIO_DEVICE(dev);
> > @@ -261,6 +274,7 @@ static void virtio_rng_class_init(ObjectClass *klass,
> > void *data)
> > vdc->realize = virtio_rng_device_realize;
> > vdc->unrealize = virtio_rng_device_unrealize;
> > vdc->get_features = get_features;
> > + vdc->set_status = virtio_rng_set_status;
> > }
> >
> > static const TypeInfo virtio_rng_info = {
> > --
> > 2.14.3
> >
> >
>
> Regards,
> Daniel
> --
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>
