On Wed, Oct 17, 2018 at 12:10:04PM -0300, Eduardo Habkost wrote: > On Wed, Oct 17, 2018 at 10:22:37AM +0100, Stefan Hajnoczi wrote: > > On Fri, Oct 12, 2018 at 11:54:35PM -0300, Eduardo Habkost wrote: > > > This patch adds separate device types for each of those virtio > > > device flavors: > > > > > > - virtio-*-pci: the existing multi-purpose device types > > > - Configurable using `disable-legacy` and `disable-modern` > > > properties > > > - Legacy driver support is automatically enabled/disabled > > > depending on the bus where it is plugged > > > - Supports Conventional PCI and PCI Express buses > > > (but Conventional PCI is incompatible with > > > disable-legacy=off) > > > - Changes PCI vendor/device IDs at runtime > > > - virtio-*-pci-0.9: legacy virtio device > > > - Supports Conventional PCI buses only, because > > > it has a PIO BAR > > > - virtio-*-pci-1.0-transitional: virtio-1.0 device supporting legacy > > > drivers > > > - Supports Conventional PCI buses only, because > > > it has a PIO BAR > > > - virtio-*-pci-1.0: modern-only > > > - Supports both Conventional PCI and PCI Express buses > > > > If new device types are being created, is it time to decouple the VIRTIO > > PCI transport from the actual VIRTIO device (blk, net, scsi) like we > > already have with virtio-mmio? > > > > -device virtio-pci-1.0,id=virtio-pci-0 > > -device virtio-blk,bus=virtio-pci-0,drive=drive0,serial=mydisk > > > > That way we avoid lots of boilerplate code and an explosion of new > > device types. > > I don't think that would work. This would in turn make > virtio-pci-1.0 a chameleon device that changes PCI ID depending > on the backend device plugged to it. > > Also, PCI IDs are not the only information contained inside the > virtio-pci subclasses. See all the PCI-specific + > device-type-specific knowledge encoded inside the class_init and > instance_init functions of each virtio-pci subclass.
I think we need to draw the line somewhere. We can't make new classes and bother users each time there is a behaviour change in the device. But I also think the transport/device split it also an internal virtio thing, no one who has not read the spec cares about it. > -- > Eduardo
