From: Maxime Coquelin <maxime.coquelin@redhat.com>
To: Amit Prakash Shukla <amitprakashs@marvell.com>,
Chenbo Xia <chenbo.xia@intel.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
Jerin Jacob Kollanukkaran <jerinj@marvell.com>,
"stable@dpdk.org" <stable@dpdk.org>,
"Ruifeng.Wang@arm.com" <Ruifeng.Wang@arm.com>
Subject: Re: [PATCH v3] vhost: compilation fix for GCC-12
Date: Thu, 6 Oct 2022 09:24:35 +0200 [thread overview]
Message-ID: <5fe93e73-a88a-88b6-e35f-a06038cf4414@redhat.com> (raw)
In-Reply-To: <PH0PR18MB5167B80A0538126CB062C01AC85C9@PH0PR18MB5167.namprd18.prod.outlook.com>
Hi Amit,
On 10/6/22 09:22, Amit Prakash Shukla wrote:
> Ping.
I posted a patch yesterday that fixes this issue without having to
change the runtime behavior:
http://patches.dpdk.org/project/dpdk/patch/20221005203524.89336-1-maxime.coquelin@redhat.com/
Could you test it and provide ack if OK on your side?
Thanks,
Maxime
>> -----Original Message-----
>> From: Amit Prakash Shukla <amitprakashs@marvell.com>
>> Sent: Friday, September 2, 2022 8:36 PM
>> To: Maxime Coquelin <maxime.coquelin@redhat.com>; Chenbo Xia
>> <chenbo.xia@intel.com>
>> Cc: dev@dpdk.org; Jerin Jacob Kollanukkaran <jerinj@marvell.com>;
>> stable@dpdk.org; Ruifeng.Wang@arm.com; Amit Prakash Shukla
>> <amitprakashs@marvell.com>
>> Subject: [PATCH v3] vhost: compilation fix for GCC-12
>>
>> GCC-12 complains about the possible use of un-initialized array. At compile
>> time it seems like it is not able to evaluate the size as it involves run-time
>> variable and at compile time it seems like gcc assumes value of "size" variable
>> to be zero which makes gcc-12 to jump the while loop.
>> "size = pkt->pkt_len + sizeof(struct virtio_net_hdr_mrg_rxbuf);"
>>
>> As part of the fix, "while (){}" is replaced by "do {} while()" which make the
>> compiler to generate a code in which buf_vec will never be used un-
>> initialized.
>>
>> ../lib/vhost/virtio_net.c:941:35: error:
>> 'buf_vec[0].buf_len' may be used uninitialized
>> [-Werror=maybe-uninitialized]
>> 941 | buf_len = buf_vec[vec_idx].buf_len;
>> | ~~~~~~~~~~~~~~~~^~~~~~~~
>> ../lib/vhost/virtio_net.c: In function 'virtio_dev_rx_packed':
>> ../lib/vhost/virtio_net.c:1285:27: note: 'buf_vec' declared here
>> 1285 | struct buf_vector buf_vec[BUF_VECTOR_MAX];
>> | ^~~~~~~
>> cc1: all warnings being treated as errors
>>
>> Fixes: 93520085efda ("vhost: add packed ring single enqueue")
>> Cc: stable@dpdk.org
>>
>> Signed-off-by: Amit Prakash Shukla <amitprakashs@marvell.com>
>> ---
>> v2:
>> - Changes for code review suggestion
>>
>> v3:
>> - Added a description
>>
>> lib/vhost/virtio_net.c | 8 ++++----
>> 1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c index
>> b3d954aab4..9b77d3d10f 100644
>> --- a/lib/vhost/virtio_net.c
>> +++ b/lib/vhost/virtio_net.c
>> @@ -1069,7 +1069,7 @@ vhost_enqueue_single_packed(struct virtio_net
>> *dev,
>> else
>> max_tries = 1;
>>
>> - while (size > 0) {
>> + do {
>> /*
>> * if we tried all available ring items, and still
>> * can't get enough buf, it means something abnormal @@ -
>> 1097,7 +1097,7 @@ vhost_enqueue_single_packed(struct virtio_net *dev,
>> avail_idx += desc_count;
>> if (avail_idx >= vq->size)
>> avail_idx -= vq->size;
>> - }
>> + } while (size > 0);
>>
>> if (mbuf_to_desc(dev, vq, pkt, buf_vec, nr_vec, num_buffers, false)
>> < 0)
>> return -1;
>> @@ -1574,7 +1574,7 @@ vhost_enqueue_async_packed(struct virtio_net
>> *dev,
>> else
>> max_tries = 1;
>>
>> - while (size > 0) {
>> + do {
>> /*
>> * if we tried all available ring items, and still
>> * can't get enough buf, it means something abnormal @@ -
>> 1601,7 +1601,7 @@ vhost_enqueue_async_packed(struct virtio_net *dev,
>> avail_idx += desc_count;
>> if (avail_idx >= vq->size)
>> avail_idx -= vq->size;
>> - }
>> + } while (size > 0);
>>
>> if (unlikely(mbuf_to_desc(dev, vq, pkt, buf_vec, nr_vec,
>> *nr_buffers, true) < 0))
>> return -1;
>> --
>> 2.25.1
>
next prev parent reply other threads:[~2022-10-06 7:24 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-01 8:49 [PATCH] " Amit Prakash Shukla
2022-09-02 7:23 ` Ruifeng Wang
2022-09-02 11:57 ` Amit Prakash Shukla
2022-09-02 12:41 ` [PATCH v2] " Amit Prakash Shukla
2022-09-02 12:56 ` Bagas Sanjaya
2022-09-02 15:11 ` [EXT] " Amit Prakash Shukla
2022-09-02 15:06 ` [PATCH v3] " Amit Prakash Shukla
2022-10-06 7:22 ` Amit Prakash Shukla
2022-10-06 7:24 ` Maxime Coquelin [this message]
2022-10-06 8:05 ` [EXT] " Amit Prakash Shukla
2022-10-06 12:35 ` David Marchand
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