linux-kernel - [PATCH 3/3] virtio-pci: Use cpumask_available to fix compilation error

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Date:   Thu, 14 Apr 2022 17:08:55 +0200
From:   Christophe de Dinechin <dinechin@...hat.com>
To:     trivial@...nel.org
Cc:     Ben Segall <bsegall@...gle.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>, Mel Gorman <mgorman@...e.de>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org,
        Zhen Lei <thunder.leizhen@...wei.com>,
        Christophe de Dinechin <dinechin@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH 3/3] virtio-pci: Use cpumask_available to fix compilation error

With GCC 12 and defconfig, we get the following error:

|   CC      drivers/virtio/virtio_pci_common.o
| drivers/virtio/virtio_pci_common.c: In function ‘vp_del_vqs’:
| drivers/virtio/virtio_pci_common.c:257:29: error: the comparison will
|  always evaluate as ‘true’ for the pointer operand in
|  ‘vp_dev->msix_affinity_masks + (sizetype)((long unsigned int)i * 8)’
|  must not be NULL [-Werror=address]
|   257 |                         if (vp_dev->msix_affinity_masks[i])
|       |                             ^~~~~~

This happens in the case where CONFIG_CPUMASK_OFFSTACK is not defined,
since we typedef cpumask_var_t as an array. The compiler is essentially
complaining that an array pointer cannot be NULL. This is not a very
important warning, but there is a function called cpumask_available that
seems to be defined just for that case, so the fix is easy.

Signed-off-by: Christophe de Dinechin <christophe@...echin.org>
Signed-off-by: Christophe de Dinechin <dinechin@...hat.com>
---
 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 d724f676608b..5c44a2f13c93 100644
--- a/drivers/virtio/virtio_pci_common.c
+++ b/drivers/virtio/virtio_pci_common.c
@@ -254,7 +254,7 @@ void vp_del_vqs(struct virtio_device *vdev)
 
 	if (vp_dev->msix_affinity_masks) {
 		for (i = 0; i < vp_dev->msix_vectors; i++)
-			if (vp_dev->msix_affinity_masks[i])
+			if (cpumask_available(vp_dev->msix_affinity_masks[i]))
 				free_cpumask_var(vp_dev->msix_affinity_masks[i]);
 	}
 
-- 
2.35.1