On Sunday 21 September 2014 13:21:06, Michael S. Tsirkin wrote: > On Sun, Sep 21, 2014 at 11:36:44AM +0200, Stefan Fritsch wrote: > > On Sunday 21 September 2014 11:09:14, Michael S. Tsirkin wrote: > > > On Thu, Sep 18, 2014 at 09:18:37PM +0200, Stefan Fritsch wrote: > > > > On Monday 01 September 2014 09:37:30, Michael S. Tsirkin wrote: > > > > > Why do we need INT#x? > > > > > How about setting IRQF_SHARED for the config interrupt > > > > > while using MSI-X? You'd have to read ISR to check that the > > > > > interrupt was intended for your device. > > > > > > > > > > > > > > > > The virtio 0.9.5 spec says that ISR is "unused" when in MSI-X > > > > mode. I don't think that you can depend on the device to set > > > > the > > > > configuration changed bit. > > > > The virtio 1.0 spec seems to have fixed that. > > > > > > > > > > > > Yes, virtio 0.9.5 has this bug. But in practice qemu always set > > > this bit, so for qemu we could do that > > > unconditionally. Pekka's lkvm tool doesn't > > > unfortunately. It's easy to fix that, but it would be nicer to > > > additionally probe for old versions of the tool, and disable > > > IRQF_SHARED in that case. > > > > > > > > What about other implementations? I think Linux should try to > > conform to the spec so that all device implementations which > > conform to the spec just work. > > > > > > > > One implementation that comes to mind is virtualbox. But from a > > quick look at the source, it seems that it sets the ISR bit > > always, too. And it uses qemu's subsystem vendor id. > > > > > > > > But there are other implementations. For example bhyve. > > I couldn't find any code in bhyve that sets VTCFG_ISR_CONF_CHANGED. > Maybe it doesn't generate config changed interrupts? > > bhyve sets subsystem vendor to 0 apparently? > We could use that to detect it. My point was that there are many virtio implementations by now and you can't assume you know all of them. > But maybe we should just make it a 1.0 only feature. FWIW, I think that would be the better option. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
