Re: [PATCH v1] s390/virtio_ccw: don't allocate/assign airqs for non-existing queues

[Michael S. Tsirkin]

Wow great job digging through all these hypervisors!

On Mon, Apr 07, 2025 at 10:38:59AM +0200, David Hildenbrand wrote:
> crossvm:
> https://github.com/google/crosvm/blob/main/devices/src/virtio/balloon.rs
> 
> -> Hard-codes queue numbers; does *not* offer/implement
>    VIRTIO_BALLOON_F_STATS_VQ but does offer VIRTIO_BALLOON_F_STATS_VQ
>    and VIRTIO_BALLOON_F_DEFLATE_ON_OOM.
> 
> -> Implements something that is not in the virtio-spec
> 
> const VIRTIO_BALLOON_F_WS_REPORTING: u32 = 8; // Working Set Reporting
> virtqueues
> 
> and
> 
> const WS_DATA_VQ: usize = 5;
> const WS_OP_VQ: usize = 6;
> 
> 
> IIUC, Linux inside cross-vm might actually be problematic? They would
> disagree on the virtqueue for free-page-reporting


That's why things must be tied to negotiated features, not to offered
ones.


> 
> Maybe I am missing something, it's a mess ...

Indeed. Let's fix the implementations while keeping work arounds for
existing ones.

-- 
MST