Re: [Qemu-devel] [PATCH v2] virtio-rng: process pending requests when driver is ready

["Daniel P. Berrangé" <berrange@redhat.com>]

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.

> 
>  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 <slopezpa@redhat.com>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> Signed-off-by: Pankaj Gupta <pagupta@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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