[PATCH] vhost: compilation fix for GCC-12

[PATCH] vhost: compilation fix for GCC-12

[Amit Prakash Shukla]

../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>
---
 lib/vhost/virtio_net.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c
index b3d954aab4..0220bc923c 100644
--- a/lib/vhost/virtio_net.c
+++ b/lib/vhost/virtio_net.c
@@ -1069,6 +1069,12 @@ vhost_enqueue_single_packed(struct virtio_net *dev,
 	else
 		max_tries = 1;
 
+	/* To avoid GCC-12 warning.
+	 * GCC-12 is not evaluating sizeof at compile time.
+	 */
+	if (unlikely(size == 0))
+		return -1;
+
 	while (size > 0) {
 		/*
 		 * if we tried all available ring items, and still
@@ -1574,6 +1580,12 @@ vhost_enqueue_async_packed(struct virtio_net *dev,
 	else
 		max_tries = 1;
 
+	/* To avoid GCC-12 warning.
+	 * GCC-12 is not evaluating sizeof at compile time.
+	 */
+	if (unlikely(size == 0))
+		return -1;
+
 	while (size > 0) {
 		/*
 		 * if we tried all available ring items, and still
-- 
2.25.1

RE: [PATCH] vhost: compilation fix for GCC-12

[Ruifeng Wang]

> -----Original Message-----
> From: Amit Prakash Shukla <amitprakashs@marvell.com>
> Sent: Thursday, September 1, 2022 4:50 PM
> To: Maxime Coquelin <maxime.coquelin@redhat.com>; Chenbo Xia <chenbo.xia@intel.com>
> Cc: dev@dpdk.org; jerinj@marvell.com; stable@dpdk.org; Amit Prakash Shukla
> <amitprakashs@marvell.com>
> Subject: [PATCH] vhost: compilation fix for GCC-12
> 
> ../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>
> ---
>  lib/vhost/virtio_net.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c index b3d954aab4..0220bc923c
> 100644
> --- a/lib/vhost/virtio_net.c
> +++ b/lib/vhost/virtio_net.c
> @@ -1069,6 +1069,12 @@ vhost_enqueue_single_packed(struct virtio_net *dev,
>  	else
>  		max_tries = 1;
> 
> +	/* To avoid GCC-12 warning.
> +	 * GCC-12 is not evaluating sizeof at compile time.
Is this a compiler behavior change against previous versions?
I tried to find some clue from gcc-12 doc but got nothing. Can you point me to any material?

> +	 */
> +	if (unlikely(size == 0))
> +		return -1;
> +
>  	while (size > 0) {
Change 'while(){}' to 'do{}while()' can be a simpler solution. What do you think?

Thanks.

>  		/*
>  		 * if we tried all available ring items, and still @@ -1574,6 +1580,12 @@
> vhost_enqueue_async_packed(struct virtio_net *dev,
>  	else
>  		max_tries = 1;
> 
> +	/* To avoid GCC-12 warning.
> +	 * GCC-12 is not evaluating sizeof at compile time.
> +	 */
> +	if (unlikely(size == 0))
> +		return -1;
> +
>  	while (size > 0) {
>  		/*
>  		 * if we tried all available ring items, and still
> --
> 2.25.1

RE: [PATCH] vhost: compilation fix for GCC-12

[Amit Prakash Shukla]

Thanks Ruifeng for the code review and feedback. Please find my response inline.

> -----Original Message-----
> From: Ruifeng Wang <Ruifeng.Wang@arm.com>
> Sent: Friday, September 2, 2022 12:54 PM
> To: Amit Prakash Shukla <amitprakashs@marvell.com>; 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; nd <nd@arm.com>
> Subject: [EXT] RE: [PATCH] vhost: compilation fix for GCC-12
> 
> External Email
> 
> ----------------------------------------------------------------------
> > -----Original Message-----
> > From: Amit Prakash Shukla <amitprakashs@marvell.com>
> > Sent: Thursday, September 1, 2022 4:50 PM
> > To: Maxime Coquelin <maxime.coquelin@redhat.com>; Chenbo Xia
> > <chenbo.xia@intel.com>
> > Cc: dev@dpdk.org; jerinj@marvell.com; stable@dpdk.org; Amit Prakash
> > Shukla <amitprakashs@marvell.com>
> > Subject: [PATCH] vhost: compilation fix for GCC-12
> >
> > ../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>
> > ---
> >  lib/vhost/virtio_net.c | 12 ++++++++++++
> >  1 file changed, 12 insertions(+)
> >
> > diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c index
> > b3d954aab4..0220bc923c
> > 100644
> > --- a/lib/vhost/virtio_net.c
> > +++ b/lib/vhost/virtio_net.c
> > @@ -1069,6 +1069,12 @@ vhost_enqueue_single_packed(struct virtio_net
> *dev,
> >  	else
> >  		max_tries = 1;
> >
> > +	/* To avoid GCC-12 warning.
> > +	 * GCC-12 is not evaluating sizeof at compile time.
> Is this a compiler behavior change against previous versions?
> I tried to find some clue from gcc-12 doc but got nothing. Can you point me to
> any material?
Apologies for the wrong wordings in the comment. In the comment I mean, it seems like 
point at which sizeof gets evaluated during compilation has changed. I am not sure on it though.
I too could not find documentation regarding the same.

> 
> > +	 */
> > +	if (unlikely(size == 0))
> > +		return -1;
> > +
> >  	while (size > 0) {
> Change 'while(){}' to 'do{}while()' can be a simpler solution. What do you
> think?
I agree, solution suggested by you is better than the one in patch. I will make the suggested
changes as part of v2. Thanks.

> 
> Thanks.
> 
> >  		/*
> >  		 * if we tried all available ring items, and still @@ -1574,6
> > +1580,12 @@ vhost_enqueue_async_packed(struct virtio_net *dev,
> >  	else
> >  		max_tries = 1;
> >
> > +	/* To avoid GCC-12 warning.
> > +	 * GCC-12 is not evaluating sizeof at compile time.
> > +	 */
> > +	if (unlikely(size == 0))
> > +		return -1;
> > +
> >  	while (size > 0) {
> >  		/*
> >  		 * if we tried all available ring items, and still
> > --
> > 2.25.1

[PATCH v2] vhost: compilation fix for GCC-12

[Amit Prakash Shukla]

../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

 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

Re: [PATCH v2] vhost: compilation fix for GCC-12

[Bagas Sanjaya]

[-- Attachment #1: Type: text/plain, Size: 1054 bytes --]

On Fri, Sep 02, 2022 at 06:11:52PM +0530, Amit Prakash Shukla wrote:
> ../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

Please describe what this patch is doing (the current state of code,
why it errored, and how it is fixing the error). Write the description
in imperative mood. I don't see the description other than error message
above.

Also, for stable patches submission, Cc stable@vger.kernel.org.

Thanks.

-- 
An old man doll... just what I always wanted! - Clara

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 228 bytes --]

RE: [EXT] Re: [PATCH v2] vhost: compilation fix for GCC-12

[Amit Prakash Shukla]

Thanks for the feedback.

> -----Original Message-----
> From: Bagas Sanjaya <bagasdotme@gmail.com>
> Sent: Friday, September 2, 2022 6:26 PM
> To: Amit Prakash Shukla <amitprakashs@marvell.com>
> Cc: Maxime Coquelin <maxime.coquelin@redhat.com>; Chenbo Xia
> <chenbo.xia@intel.com>; dev@dpdk.org; Jerin Jacob Kollanukkaran
> <jerinj@marvell.com>; stable@dpdk.org; Ruifeng.Wang@arm.com
> Subject: [EXT] Re: [PATCH v2] vhost: compilation fix for GCC-12
> 
> External Email
> 
> ----------------------------------------------------------------------
> On Fri, Sep 02, 2022 at 06:11:52PM +0530, Amit Prakash Shukla wrote:
> > ../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
> 
> Please describe what this patch is doing (the current state of code, why it
> errored, and how it is fixing the error). Write the description in imperative
> mood. I don't see the description other than error message above.
I have pushed v3 incorporating your suggestion regarding description.

> 
> Also, for stable patches submission, Cc stable@vger.kernel.org.
> 
> Thanks.
> 
> --
> An old man doll... just what I always wanted! - Clara

[PATCH v3] vhost: compilation fix for GCC-12

[Amit Prakash Shukla]

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

RE: [PATCH v3] vhost: compilation fix for GCC-12

[Amit Prakash Shukla]

Ping. 

> -----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

Re: [PATCH v3] vhost: compilation fix for GCC-12

[Maxime Coquelin]

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
> 

RE: [EXT] Re: [PATCH v3] vhost: compilation fix for GCC-12

[Amit Prakash Shukla]

Hi Maxime,

Sure, I will test and reply on your patch.

Thanks,
Amit Shukla

> -----Original Message-----
> From: Maxime Coquelin <maxime.coquelin@redhat.com>
> Sent: Thursday, October 6, 2022 12:55 PM
> To: Amit Prakash Shukla <amitprakashs@marvell.com>; Chenbo Xia
> <chenbo.xia@intel.com>
> Cc: dev@dpdk.org; Jerin Jacob Kollanukkaran <jerinj@marvell.com>;
> stable@dpdk.org; Ruifeng.Wang@arm.com
> Subject: [EXT] Re: [PATCH v3] vhost: compilation fix for GCC-12
> 
> External Email
> 
> ----------------------------------------------------------------------
> 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:
> 
> https://urldefense.proofpoint.com/v2/url?u=http-
> 3A__patches.dpdk.org_project_dpdk_patch_20221005203524.89336-2D1-
> 2Dmaxime.coquelin-
> 40redhat.com_&d=DwICaQ&c=nKjWec2b6R0mOyPaz7xtfQ&r=ALGdXl3fZgFG
> R69VnJLdSnADun7zLaXG1p5Rs7pXihE&m=vDZyV-
> pKSmtssm0L8YUPR6doPgIw44tOh3xWgNEwD3FGjqEomaP9lcYLhrbqwGKb&s
> =g54ujCkU-mDT0CQoJgqYlDllGLuzWs8lLa6YMzPfqkw&e=
> 
> 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
> >

Re: [EXT] Re: [PATCH v3] vhost: compilation fix for GCC-12

[David Marchand]

On Thu, Oct 6, 2022 at 10:05 AM Amit Prakash Shukla
<amitprakashs@marvell.com> wrote:
>
> Hi Maxime,
>
> Sure, I will test and reply on your patch.

Thomas merged Maxime alternative.
Marking this patch as rejected.


Thanks.

-- 
David Marchand