Re: [Qemu-devel] [PATCH] virtio: Provide version-specific variants of virtio PCI devices

[Stefan Hajnoczi]

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.

Stefan

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