Re: [PATCH net-next v5 13/15] virtio-net: support AF_XDP zc rx

[kernel test robot <lkp@intel.com>]

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Hi Xuan,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on net-next/master]

url:    https://github.com/0day-ci/linux/commits/Xuan-Zhuo/virtio-net-support-xdp-socket-zero-copy/20210617-033438
base:   https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git c7654495916e109f76a67fd3ae68f8fa70ab4faa
config: x86_64-randconfig-a015-20210617 (attached as .config)
compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 64720f57bea6a6bf033feef4a5751ab9c0c3b401)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install x86_64 cross compiling tool for clang build
        # apt-get install binutils-x86-64-linux-gnu
        # https://github.com/0day-ci/linux/commit/f5f1e60139e7c38fbb4ed58d503e89bbb26c1464
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Xuan-Zhuo/virtio-net-support-xdp-socket-zero-copy/20210617-033438
        git checkout f5f1e60139e7c38fbb4ed58d503e89bbb26c1464
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

>> drivers/net/virtio/virtio_net.c:1304:2: warning: variable 'oom' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
           if (fill_recv_xsk(vi, rq, gfp))
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/compiler.h:56:28: note: expanded from macro 'if'
   #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
                              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/compiler.h:58:30: note: expanded from macro '__trace_if_var'
   #define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond))
                                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   drivers/net/virtio/virtio_net.c:1329:10: note: uninitialized use occurs here
           return !oom;
                   ^~~
   drivers/net/virtio/virtio_net.c:1304:2: note: remove the 'if' if its condition is always false
           if (fill_recv_xsk(vi, rq, gfp))
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/compiler.h:56:23: note: expanded from macro 'if'
   #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
                         ^
   drivers/net/virtio/virtio_net.c:1297:10: note: initialize the variable 'oom' to silence this warning
           bool oom;
                   ^
                    = 0
   1 warning generated.


vim +1304 drivers/net/virtio/virtio_net.c

  1285	
  1286	/*
  1287	 * Returns false if we couldn't fill entirely (OOM).
  1288	 *
  1289	 * Normally run in the receive path, but can also be run from ndo_open
  1290	 * before we're receiving packets, or from refill_work which is
  1291	 * careful to disable receiving (using napi_disable).
  1292	 */
  1293	static bool try_fill_recv(struct virtnet_info *vi, struct receive_queue *rq,
  1294				  gfp_t gfp)
  1295	{
  1296		int err;
  1297		bool oom;
  1298	
  1299		/* Because virtio-net does not yet support flow direct, all rx
  1300		 * channels must also process other non-xsk packets. If there is
  1301		 * no buf available from xsk temporarily, we try to allocate
  1302		 * memory to the channel.
  1303		 */
> 1304		if (fill_recv_xsk(vi, rq, gfp))
  1305			goto kick;
  1306	
  1307		do {
  1308			if (vi->mergeable_rx_bufs)
  1309				err = add_recvbuf_mergeable(vi, rq, gfp);
  1310			else if (vi->big_packets)
  1311				err = add_recvbuf_big(vi, rq, gfp);
  1312			else
  1313				err = add_recvbuf_small(vi, rq, gfp);
  1314	
  1315			oom = err == -ENOMEM;
  1316			if (err)
  1317				break;
  1318		} while (rq->vq->num_free);
  1319	
  1320	kick:
  1321		if (virtqueue_kick_prepare(rq->vq) && virtqueue_notify(rq->vq)) {
  1322			unsigned long flags;
  1323	
  1324			flags = u64_stats_update_begin_irqsave(&rq->stats.syncp);
  1325			rq->stats.kicks++;
  1326			u64_stats_update_end_irqrestore(&rq->stats.syncp, flags);
  1327		}
  1328	
  1329		return !oom;
  1330	}
  1331	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

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