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Subject[PATCH 5.5 275/367] virtio-pci: check name when counting MSI-X vectors
From: Daniel Verkamp <>

commit 303090b513fd1ee45aa1536b71a3838dc054bc05 upstream.

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).

Fixes: 86a559787e6f ("virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_HINT")
Reviewed-by: Cornelia Huck <>
Signed-off-by: Daniel Verkamp <>
Signed-off-by: Michael S. Tsirkin <>
Reviewed-by: Wang, Wei W <>
Signed-off-by: Greg Kroah-Hartman <>

drivers/virtio/virtio_pci_common.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- 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 virti
/* 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])
} else {
/* Second best: one for change, shared for all vqs. */

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