Re: [Qemu-devel] [PATCH v2] virtio-pci: error out when both legacy and modern modes are disabled

[Marcel Apfelbaum <marcel.apfelbaum@gmail.com>]

On 07/21/2016 06:52 PM, Greg Kurz wrote:
> From: Greg Kurz <gkurz@linux.vnet.ibm.com>
>
> Without presuming if we got there because of a user mistake or some
> more subtle bug in the tooling, it really does not make sense to
> implement a non-functional device.
>
> Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
> Signed-off-by: Greg Kurz <groug@kaod.org>
> ---
> v2: - error out at realize time as suggested by Connie
>      - updated title and changelog
> ---
>   hw/virtio/virtio-pci.c |    6 ++++++
>   1 file changed, 6 insertions(+)
>
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index f0677b73d860..8d707aac0c21 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -1838,6 +1838,12 @@ static void virtio_pci_dc_realize(DeviceState *qdev, Error **errp)
>       VirtIOPCIProxy *proxy = VIRTIO_PCI(qdev);
>       PCIDevice *pci_dev = &proxy->pci_dev;
>
> +    if (proxy->flags & VIRTIO_PCI_FLAG_DISABLE_LEGACY &&
> +        proxy->flags & VIRTIO_PCI_FLAG_DISABLE_MODERN) {
> +        error_setg(errp, "device is unserviceable when both legacy and modern modes are disabled. At least one of the disable-modern or disable-legacy properties should be set to false.");
> +        return;
> +    }
> +

Hi Greg,

I agree with the patch, but other patch in the mailing list
replaces the flags with standalone fields:

https://lists.gnu.org/archive/html/qemu-devel/2016-07/msg04744.html

Also the error line may be too long and need to be truncated.

Thanks,
Marcel

>       if (!(proxy->flags & VIRTIO_PCI_FLAG_DISABLE_PCIE) &&
>           !(proxy->flags & VIRTIO_PCI_FLAG_DISABLE_MODERN)) {
>           pci_dev->cap_present |= QEMU_PCI_CAP_EXPRESS;
>
>