Re: [Qemu-devel] [PATCH v3] virtio-pci: error out when both legacy and modern modes are disabled

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

On 07/21/2016 08:43 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>
> ---
> v3: - rebased on top of:
>      https://lists.gnu.org/archive/html/qemu-devel/2016-07/msg04744.html
>      - use virtio_pci_legacy/modern helpers
>      - rephrased error message to be shorter and use the on/off logic
>
> Marcel, this still results in > 80 char line in the code but I'd rather not
> split it to ease grepping, nor shorten the message even more to keep it
> meaningful.
> ---
>   hw/virtio/virtio-pci.c |    5 +++++
>   1 file changed, 5 insertions(+)
>
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index 755f9218b77d..1f5f00a50a0b 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -1842,6 +1842,11 @@ static void virtio_pci_dc_realize(DeviceState *qdev, Error **errp)
>       VirtIOPCIProxy *proxy = VIRTIO_PCI(qdev);
>       PCIDevice *pci_dev = &proxy->pci_dev;
>
> +    if (!(virtio_pci_modern(proxy) || virtio_pci_legacy(proxy))) {

Hi Greg,
Thanks for rebasing it.

A minor thing, disable-legacy is now auto/on/off.
If the user sets [disable-legacy=auto, disable-modern=on]
will not pass this test, but is possible that later on
will be enabled:
See virtio_pci_realize:
        if (proxy->disable_legacy == ON_OFF_AUTO_AUTO) {
           proxy->disable_legacy = pcie_port ? ON_OFF_AUTO_ON : ON_OFF_AUTO_OFF;
        }

On the the other hand, if the user sets disable-modern=on, is reasonable to ask
him to set disable-legacy to off.


Reviewed-by: Marcel Apfelbaum <marcel@redhat.com>

Thanks,
Marcel



> +        error_setg(errp, "device cannot work when both disable-modern and disable-legacy are set to on.");
> +        return;
> +    }
> +
>       if (!(proxy->flags & VIRTIO_PCI_FLAG_DISABLE_PCIE) &&
>           virtio_pci_modern(proxy)) {
>           pci_dev->cap_present |= QEMU_PCI_CAP_EXPRESS;
>