From: Christophe Marie Francois Dupont de Dinechin <cdupontd@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Christophe de Dinechin <dinechin@redhat.com>,
trivial@kernel.org, Ben Segall <bsegall@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@redhat.com>, Mel Gorman <mgorman@suse.de>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Paolo Bonzini <pbonzini@redhat.com>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Jason Wang <jasowang@redhat.com>,
virtualization@lists.linux-foundation.org,
linux-kernel@vger.kernel.org,
Zhen Lei <thunder.leizhen@huawei.com>,
Juri Lelli <juri.lelli@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Murilo Opsfelder Araujo <muriloo@linux.ibm.com>
Subject: Re: [PATCH 3/3] virtio-pci: Use cpumask_available to fix compilation error
Date: Thu, 28 Apr 2022 11:48:01 +0200 [thread overview]
Message-ID: <3D264F7F-624D-4E9D-A139-F1DB0CC6045C@redhat.com> (raw)
In-Reply-To: <20220415044657-mutt-send-email-mst@kernel.org>
> 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
>
next prev parent reply other threads:[~2022-04-28 9:57 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-14 15:08 [PATCH 0/3] trivial: Fix several compilation errors/warnings with GCC12 Christophe de Dinechin
2022-04-14 15:08 ` [PATCH 1/3] sched/headers: Fix compilation error with GCC 12 Christophe de Dinechin
2022-04-14 15:21 ` Peter Zijlstra
2022-04-14 20:30 ` Andrew Morton
2022-04-17 15:52 ` Peter Zijlstra
2022-04-20 18:45 ` Kees Cook
2022-04-21 7:32 ` Peter Zijlstra
2022-04-25 14:23 ` Christophe de Dinechin
2022-04-17 13:27 ` David Laight
2022-04-25 14:07 ` Christophe de Dinechin
2022-05-19 11:16 ` Peter Zijlstra
2022-04-14 15:08 ` [PATCH 2/3] nodemask.h: Fix compilation error with GCC12 Christophe de Dinechin
2022-04-14 15:23 ` Peter Zijlstra
2022-04-14 15:08 ` [PATCH 3/3] virtio-pci: Use cpumask_available to fix compilation error Christophe de Dinechin
2022-04-15 8:48 ` Michael S. Tsirkin
2022-04-28 9:48 ` Christophe Marie Francois Dupont de Dinechin [this message]
2022-04-28 11:06 ` Michael S. Tsirkin
2022-05-15 21:24 ` [PATCH 0/3] trivial: Fix several compilation errors/warnings with GCC12 Davidlohr Bueso
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