From mboxrd@z Thu Jan  1 00:00:00 1970
From: Cornelia Huck <cohuck@redhat.com>
Subject: Re: [PATCH 2/2] virtio-pci: check name when counting MSI-X vectors
Date: Wed, 18 Dec 2019 10:30:36 +0100
Message-ID: <20191218103036.1ec596ff.cohuck@redhat.com>
References: <20191217190610.248061-1-dverkamp@chromium.org>
 <20191217190610.248061-2-dverkamp@chromium.org>
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To: Daniel Verkamp <dverkamp@chromium.org>
Cc: "Michael S. Tsirkin" <mst@redhat.com>, virtualization@lists.linux-foundation.org
List-Id: virtualization@lists.linuxfoundation.org

On Tue, 17 Dec 2019 11:06:10 -0800
Daniel Verkamp <dverkamp@chromium.org> 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>
> ---
>  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. */

Reviewed-by: Cornelia Huck <cohuck@redhat.com>