[PATCH net-next v2] net: mana: hardening: Reject zero max_num_queues from GDMA_QUERY_MAX_RESOURCES

[Erni Sri Satya Vennela <ernis@linux.microsoft.com>]

In a CVM environment, hardware responses cannot be trusted. The
GDMA_QUERY_MAX_RESOURCES command returns resource limits used to
determine the maximum number of queues.

In mana_gd_query_max_resources(), gc->max_num_queues is initialized
from num_online_cpus() and successively clamped by the hardware-reported
max_eq, max_cq, max_sq, max_rq, and num_msix_usable values. If any of
these hardware values is zero, gc->max_num_queues becomes zero and the
function returns success. This leads to a confusing failure later when
alloc_etherdev_mq() is called with zero queues, returning NULL and
producing a misleading -ENOMEM error.

Add an explicit zero check for gc->max_num_queues after all clamping
steps and return -ENOSPC for a clear early failure, consistent with the
existing gc->num_msix_usable <= 1 guard.

Signed-off-by: Erni Sri Satya Vennela <ernis@linux.microsoft.com>
---
Changes in v2:
* Rebase to latest main.
---
 drivers/net/ethernet/microsoft/mana/gdma_main.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/ethernet/microsoft/mana/gdma_main.c b/drivers/net/ethernet/microsoft/mana/gdma_main.c
index 098fbda0d128..f3316e929175 100644
--- a/drivers/net/ethernet/microsoft/mana/gdma_main.c
+++ b/drivers/net/ethernet/microsoft/mana/gdma_main.c
@@ -194,6 +194,9 @@ static int mana_gd_query_max_resources(struct pci_dev *pdev)
 	if (gc->max_num_queues > gc->num_msix_usable - 1)
 		gc->max_num_queues = gc->num_msix_usable - 1;
 
+	if (gc->max_num_queues == 0)
+		return -ENOSPC;
+
 	return 0;
 }
 
-- 
2.34.1