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Date: Thu, 21 Jul 2016 19:02:39 +0200
From: Greg Kurz <groug@kaod.org>
Message-ID: <20160721190239.0153576f@bahia.lan>
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Subject: Re: [Qemu-devel] [PATCH v2] virtio-pci: error out when both legacy
 and modern modes are disabled
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To: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>, Cornelia Huck <cornelia.huck@de.ibm.com>, qemu-devel@nongnu.org

On Thu, 21 Jul 2016 19:52:28 +0300
Marcel Apfelbaum <marcel.apfelbaum@gmail.com> wrote:

> 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
> 

v3 will be using virtio_pci_legacy() and virtio_pci_modern().

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

I'll rephrase the message. BTW is there a formal limit for the length
of error lines ? 80 chars ?

> 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;
> >
> >  
>