Hi Shreyansh,
First of all, thank you for your work, I was expecting a virtio sound device for some time...
You're welcome :)
Le 04/05/2021 à 21:35, Shreyansh Chouhan a écrit :
> On Tue, 4 May 2021 at 19:02, Laurent Vivier <laurent@vivier.eu <mailto:laurent@vivier.eu>> wrote:
>
> There is nothing specific to PCI in that code, why do you prevent the use of virtio-snd as a MMIO
> device?
>
> I am sorry I do not understand your question completely. If by preventing the use of virtio-snd, you
> mean
> why did I add the PCI dependencies to the Kconfig file, then I think I must have been a bit confused
> while writing it. VIRTIO_PCI already includes those dependencies, I will change the dependency to
> VIRTIO. (Which is what it is for other virtio devices too.)
>
> However if you mean why did I not add an MMIO binding for this device, then there is no
> specific reason. I simply followed what QEMU had been doing for the other virtio devices.
> Will there be any advantages to implementing the device as a MMIO device?
No, the question was only about the dependencies, generally a a virtio device is binded to a virtio
bus, and virtio PCI is a PCI card providing a virtio bus with the virtio device attached to it.
For instance, for virtio-net-pci:
HOST
-> PCI Host controller
-> PCI virtio net device (TYPE_VIRTIO_NET_PCI)
-> virtio Bus (TYPE_VIRTIO_BUS)
-> virtio net device (TYPE_VIRTIO_NET)
TYPE_VIRTIO_NET_PCI is created by hw/virtio/virtio-net-pci.c and TYPE_VIRTIO_NET by hw/net/vrtio-net.c:
hw/virtio/meson.build:
virtio_pci_ss.add(when: 'CONFIG_VIRTIO_NET', if_true: files('virtio-net-pci.c'))
virtio_ss.add_all(when: 'CONFIG_VIRTIO_PCI', if_true: virtio_pci_ss)
hw/net/meson.build
specific_ss.add(when: 'CONFIG_VIRTIO_NET', if_true: files('virtio-net.c'))
hw/net/Kconfig:
config VIRTIO_NET
bool
default y
depends on VIRTIO
So:
the virtio-net device is built when VIRTIO_NET is set,
the virtio-net-pci device is build when VIRTIO_NET and VIRTIO_PCI are set.
So what I expect for virtio-snd:
hw/virtio/meson.build:
virtio_pci_ss.add(when: 'CONFIG_VIRTIO_SND', if_true: files('virtio-snd-pci.c'))
hw/audio/meson.build:
softmmu_ss.add(when: 'CONFIG_VIRTIO_SND', if_true: files('virtio-snd.c'))
hw/audio/Kconfig
config VIRTIO_SND
bool
default y
depends on VIRTIO
With that kind of config, a machine without PCI bus will be able to create a virtio bus to add your
virtio device (like s390x with virtio-ccw of any other MMIO machine like the virt machines).
Thanks a lot for the detailed explanation. It clarifies everything regarding the separate
pci and device source files and how they are built, which was confusing me a little bit.
I will fix the meson.build and Kconfig files in the upcoming versions of these patches.
In short: update your hw/audio/config, and all will be fine.
Thanks,
Laurent
--
Thanks
Shreyansh