On 12/17/2019 07:14 AM, Daniel Verkamp wrote:
After 86a559787e6f ("virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_HINT"),
the virtio-balloon device unconditionally specifies 4 virtqueues as the
argument to find_vqs(), which means that 5 MSI-X vectors are required in
order to assign one vector per VQ plus one for configuration changes.
However, in cases where the virtio device only provides exactly as many
MSI-X vectors as required for the features it implements (e.g. 3 for the
basic configuration of inflate + deflate + config), this results in the
selection of the fallback configuration where one interrupt vector is
used for all VQs instead of having one VQ per vector.
I'm not sure if I get the above. Virtio won't do any vq allocation for
the one that has "callbacks[i] = NULL", so no msi-x vector will be
assigned for it.
Btw, did you trigger any bug with the existing code?
Best,
Wei
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