Re: [PATCH 2/2] virtio-pci: check name when counting MSI-X vectors

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Dec 17, 2019 at 11:06:10AM -0800, Daniel Verkamp wrote:
> VQs without a name specified are not valid; they are skipped in the
> later loop that assigns MSI-X vectors to queues, but the per_vq_vectors
> loop above that counts the required number of vectors previously still
> counted any queue with a non-NULL callback as needing a vector.
> 
> Add a check to the per_vq_vectors loop so that vectors with no name are
> not counted to make the two loops consistent.  This prevents
> over-counting unnecessary vectors (e.g. for features which were not
> negotiated with the device).
> 
> Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>

And I'll add:
Fixes: 9564e138b1f6 ("virtio: Add memory statistics reporting to the balloon driver (V4)")

here too.

> ---
>  drivers/virtio/virtio_pci_common.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
> index f2862f66c2ac..222d630c41fc 100644
> --- a/drivers/virtio/virtio_pci_common.c
> +++ b/drivers/virtio/virtio_pci_common.c
> @@ -294,7 +294,7 @@ static int vp_find_vqs_msix(struct virtio_device *vdev, unsigned nvqs,
>  		/* Best option: one for change interrupt, one per vq. */
>  		nvectors = 1;
>  		for (i = 0; i < nvqs; ++i)
> -			if (callbacks[i])
> +			if (names[i] && callbacks[i])
>  				++nvectors;
>  	} else {
>  		/* Second best: one for change, shared for all vqs. */
> -- 
> 2.24.1.735.g03f4e72817-goog