Re: [Qemu-devel] [PATCH v3 2/5] hw/pci: introduce pcie-pci-bridge device

[Marcel Apfelbaum]

On 01/08/2017 18:51, Michael S. Tsirkin wrote:
> On Tue, Aug 01, 2017 at 06:45:13PM +0300, Marcel Apfelbaum wrote:
> > On 01/08/2017 18:32, Michael S. Tsirkin wrote:
> > > On Mon, Jul 31, 2017 at 09:40:41PM +0300, Alexander Bezzubikov wrote:
> > > > > > +typedef struct PCIEPCIBridge {
> > > > > > +    /*< private >*/
> > > > > > +    PCIBridge parent_obj;
> > > > > > +
> > > > > > +    bool msi_enable;
> > > > >
> > > > >
> > > > > Please rename the msi_enable property to "msi" in order
> > > > > to be aligned with the existent PCIBridgeDev and
> > > > > consider making it OnOffAuto for the same reason.
> > > > > (I am not sure about the last part though, we have
> > > > >    no meaning for "auto" here)
> > > >
> > > > Agreed about "msi", but OnOffAuto looks weird to me
> > > > as we always want MSI to be enabled.
> >
> > Hi Michael,
> >
> > > Why even have a property then? Can't you enable it unconditionally?
> >
> > Because of a current bug in Linux kernel:
> >     https://www.spinics.net/lists/linux-pci/msg63052.html
> > msi will not work until the patch is merged. Even when
> > it will be merged, not all linux kernels will contain the patch.
>
> You should Cc stable to make sure they all gain it eventually.

Right! thanks, we missed cc-ing stable.
Added stable to the mail thread.
Marcel


> > Disabling msi is a workaround for the above case.
> >
> > Thanks,
> > Marcel
>
> Really enabling MSI without bus master is a bug that I'm not 100% sure
> it even worth working around. But I guess it's not too bad to have a
> work-around given it's this simple.