[PATCH v2] virtio-net: Fix the interpretation of max_tx_vq

[Akihiko Odaki <akihiko.odaki@daynix.com>]

virtio-net uses the max_tx_vq field of struct virtio_net_rss_config to
determine the number of queue pairs and emits an error message saying
"Can't get queue_pairs". However, the field tells only about tx.

Examine unclassified_queue and indirection_table to determine the number
of queues required for rx, and correct the name of field in the error
message, clarifying its correct semantics.

Fixes: 590790297c0d ("virtio-net: implement RSS configuration command")
Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
---
Changes in v2:
- Handled unclassified_queue too.
- Added a Fixes: tag.
- Link to v1: https://lore.kernel.org/qemu-devel/20250321-vq-v1-1-6d6d285e5cbc@daynix.com
---
 hw/net/virtio-net.c | 26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index de87cfadffe1..afc6b82f13c9 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -1450,23 +1450,29 @@ static uint16_t virtio_net_handle_rss(VirtIONet *n,
         err_value = (uint32_t)s;
         goto error;
     }
-    for (i = 0; i < n->rss_data.indirections_len; ++i) {
-        uint16_t val = n->rss_data.indirections_table[i];
-        n->rss_data.indirections_table[i] = virtio_lduw_p(vdev, &val);
-    }
     offset += size_get;
     size_get = sizeof(temp);
     s = iov_to_buf(iov, iov_cnt, offset, &temp, size_get);
     if (s != size_get) {
-        err_msg = "Can't get queue_pairs";
+        err_msg = "Can't get max_tx_vq";
         err_value = (uint32_t)s;
         goto error;
     }
-    queue_pairs = do_rss ? virtio_lduw_p(vdev, &temp.us) : n->curr_queue_pairs;
-    if (queue_pairs == 0 || queue_pairs > n->max_queue_pairs) {
-        err_msg = "Invalid number of queue_pairs";
-        err_value = queue_pairs;
-        goto error;
+    if (do_rss) {
+        queue_pairs = MAX(virtio_lduw_p(vdev, &temp.us),
+                          n->rss_data.default_queue);
+        for (i = 0; i < n->rss_data.indirections_len; ++i) {
+            uint16_t val = n->rss_data.indirections_table[i];
+            n->rss_data.indirections_table[i] = virtio_lduw_p(vdev, &val);
+            queue_pairs = MAX(queue_pairs, n->rss_data.indirections_table[i]);
+        }
+        if (queue_pairs == 0 || queue_pairs > n->max_queue_pairs) {
+            err_msg = "Invalid number of queue_pairs";
+            err_value = queue_pairs;
+            goto error;
+        }
+    } else {
+        queue_pairs = n->curr_queue_pairs;
     }
     if (temp.b > VIRTIO_NET_RSS_MAX_KEY_SIZE) {
         err_msg = "Invalid key size";

---
base-commit: 825b96dbcee23d134b691fc75618b59c5f53da32
change-id: 20250321-vq-87aff4f531bf

Best regards,
-- 
Akihiko Odaki <akihiko.odaki@daynix.com>