Re: [PATCH 1/2] pc-bios/s390-ccw/virtio: Set missing status bits while initializing

[Eric Farman]

On Thu, 2022-06-23 at 09:11 +0200, Thomas Huth wrote:
> According chapter "3.1.1 Driver Requirements: Device Initialization"
> of the Virtio specification (v1.1), a driver for a device has to set
> the ACKNOWLEDGE and DRIVER bits in the status field after resetting
> the device. The s390-ccw bios skipped these steps so far and seems
> like QEMU never cared. Anyway, it's better to follow the spec, so
> let's set these bits now in the right spots, too.
> 
> Signed-off-by: Thomas Huth <thuth@redhat.com>

Reviewed-by: Eric Farman <farman@linux.ibm.com>

> ---
>  pc-bios/s390-ccw/virtio.c | 18 ++++++++++++++----
>  1 file changed, 14 insertions(+), 4 deletions(-)
> 
> diff --git a/pc-bios/s390-ccw/virtio.c b/pc-bios/s390-ccw/virtio.c
> index 5d2c6e3381..4e85a2eb82 100644
> --- a/pc-bios/s390-ccw/virtio.c
> +++ b/pc-bios/s390-ccw/virtio.c
> @@ -220,7 +220,7 @@ int virtio_run(VDev *vdev, int vqid, VirtioCmd
> *cmd)
>  void virtio_setup_ccw(VDev *vdev)
>  {
>      int i, rc, cfg_size = 0;
> -    unsigned char status = VIRTIO_CONFIG_S_DRIVER_OK;
> +    uint8_t status;
>      struct VirtioFeatureDesc {
>          uint32_t features;
>          uint8_t index;
> @@ -234,6 +234,10 @@ void virtio_setup_ccw(VDev *vdev)
>  
>      run_ccw(vdev, CCW_CMD_VDEV_RESET, NULL, 0, false);
>  
> +    status = VIRTIO_CONFIG_S_ACKNOWLEDGE;
> +    rc = run_ccw(vdev, CCW_CMD_WRITE_STATUS, &status,
> sizeof(status), false);
> +    IPL_assert(rc == 0, "Could not write ACKNOWLEDGE status to
> host");
> +
>      switch (vdev->senseid.cu_model) {
>      case VIRTIO_ID_NET:
>          vdev->nr_vqs = 2;
> @@ -253,6 +257,11 @@ void virtio_setup_ccw(VDev *vdev)
>      default:
>          panic("Unsupported virtio device\n");
>      }
> +
> +    status |= VIRTIO_CONFIG_S_DRIVER;
> +    rc = run_ccw(vdev, CCW_CMD_WRITE_STATUS, &status,
> sizeof(status), false);
> +    IPL_assert(rc == 0, "Could not write DRIVER status to host");
> +
>      IPL_assert(
>          run_ccw(vdev, CCW_CMD_READ_CONF, &vdev->config, cfg_size,
> false) == 0,
>         "Could not get block device configuration");
> @@ -291,9 +300,10 @@ void virtio_setup_ccw(VDev *vdev)
>              run_ccw(vdev, CCW_CMD_SET_VQ, &info, sizeof(info),
> false) == 0,
>              "Cannot set VQ info");
>      }
> -    IPL_assert(
> -        run_ccw(vdev, CCW_CMD_WRITE_STATUS, &status, sizeof(status),
> false) == 0,
> -        "Could not write status to host");
> +
> +    status |= VIRTIO_CONFIG_S_DRIVER_OK;
> +    rc = run_ccw(vdev, CCW_CMD_WRITE_STATUS, &status,
> sizeof(status), false);
> +    IPL_assert(rc == 0, "Could not write DRIVER_OK status to host");
>  }
>  
>  bool virtio_is_supported(SubChannelId schid)