Messages in this thread | | | Subject | Re: [PATCH 3/3] virtio-pci: Use cpumask_available to fix compilation error | From | Christophe Marie Francois Dupont de Dinechin <> | Date | Thu, 28 Apr 2022 11:48:01 +0200 |
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> On 15 Apr 2022, at 10:48, Michael S. Tsirkin <mst@redhat.com> wrote: > > On Thu, Apr 14, 2022 at 05:08:55PM +0200, Christophe de Dinechin wrote: >> 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@dinechin.org> >> Signed-off-by: Christophe de Dinechin <dinechin@redhat.com> > > There was an alternate patch proposed for this by > Murilo Opsfelder Araujo. What do you think about that approach?
I responded on the other thread, but let me share the response here:
[to muriloo@linux.ibm.com] Apologies for the delay in responding, broken laptop…
In the case where CONFIG_CPUMASK_OFFSTACK is not defined, we have:
typedef struct cpumask cpumask_var_t[1];
So that vp_dev->msix_affinity_masks[i] is statically not null (that’s the warning) but also a static pointer, so not kfree-safe IMO.
> > >> --- >> 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 >
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