netdev - Re: [PATCH vhost v12 10/10] virtio_net: merge dma operations when filling mergeable buffers

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Message-ID: <202307191819.0tatknWa-lkp@intel.com>
Date: Wed, 19 Jul 2023 18:33:05 +0800
From: kernel test robot <lkp@...el.com>
To: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
	virtualization@...ts.linux-foundation.org
Cc: oe-kbuild-all@...ts.linux.dev, "Michael S. Tsirkin" <mst@...hat.com>,
	Jason Wang <jasowang@...hat.com>,
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Jesper Dangaard Brouer <hawk@...nel.org>,
	John Fastabend <john.fastabend@...il.com>, netdev@...r.kernel.org,
	bpf@...r.kernel.org, Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH vhost v12 10/10] virtio_net: merge dma operations when
 filling mergeable buffers

Hi Xuan,

kernel test robot noticed the following build warnings:

[auto build test WARNING on v6.4]
[cannot apply to mst-vhost/linux-next linus/master v6.5-rc2 v6.5-rc1 next-20230719]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Xuan-Zhuo/virtio_ring-check-use_dma_api-before-unmap-desc-for-indirect/20230719-121424
base:   v6.4
patch link:    https://lore.kernel.org/r/20230719040422.126357-11-xuanzhuo%40linux.alibaba.com
patch subject: [PATCH vhost v12 10/10] virtio_net: merge dma operations when filling mergeable buffers
config: i386-randconfig-i006-20230718 (https://download.01.org/0day-ci/archive/20230719/202307191819.0tatknWa-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce: (https://download.01.org/0day-ci/archive/20230719/202307191819.0tatknWa-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@...el.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202307191819.0tatknWa-lkp@intel.com/

All warnings (new ones prefixed by >>):

   drivers/net/virtio_net.c: In function 'virtnet_rq_init_one_sg':
>> drivers/net/virtio_net.c:624:41: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
     624 |                 rq->sg[0].dma_address = (dma_addr_t)addr;
         |                                         ^
   drivers/net/virtio_net.c: In function 'virtnet_rq_alloc':
>> drivers/net/virtio_net.c:682:28: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
     682 |                 *sg_addr = (void *)(dma->addr + alloc_frag->offset - sizeof(*dma));
         |                            ^


vim +624 drivers/net/virtio_net.c

   619	
   620	static void virtnet_rq_init_one_sg(struct receive_queue *rq, void *addr, u32 len)
   621	{
   622		if (rq->do_dma) {
   623			sg_init_table(rq->sg, 1);
 > 624			rq->sg[0].dma_address = (dma_addr_t)addr;
   625			rq->sg[0].length = len;
   626		} else {
   627			sg_init_one(rq->sg, addr, len);
   628		}
   629	}
   630	
   631	static void *virtnet_rq_alloc(struct receive_queue *rq, u32 size,
   632				      void **sg_addr, gfp_t gfp)
   633	{
   634		struct page_frag *alloc_frag = &rq->alloc_frag;
   635		struct virtnet_rq_dma *dma;
   636		struct device *dev;
   637		void *buf, *head;
   638		dma_addr_t addr;
   639	
   640		if (unlikely(!skb_page_frag_refill(size, alloc_frag, gfp)))
   641			return NULL;
   642	
   643		head = (char *)page_address(alloc_frag->page);
   644	
   645		if (rq->do_dma) {
   646			dma = head;
   647	
   648			/* new pages */
   649			if (!alloc_frag->offset) {
   650				if (rq->last_dma) {
   651					/* Now, the new page is allocated, the last dma
   652					 * will not be used. So the dma can be unmapped
   653					 * if the ref is 0.
   654					 */
   655					virtnet_rq_unmap(rq, rq->last_dma, 0);
   656					rq->last_dma = NULL;
   657				}
   658	
   659				dev = virtqueue_dma_dev(rq->vq);
   660	
   661				dma->len = alloc_frag->size - sizeof(*dma);
   662	
   663				addr = dma_map_single_attrs(dev, dma + 1, dma->len, DMA_FROM_DEVICE, 0);
   664				if (addr == DMA_MAPPING_ERROR)
   665					return NULL;
   666	
   667				dma->addr = addr;
   668				dma->need_sync = dma_need_sync(dev, addr);
   669	
   670				/* Add a reference to dma to prevent the entire dma from
   671				 * being released during error handling. This reference
   672				 * will be freed after the pages are no longer used.
   673				 */
   674				get_page(alloc_frag->page);
   675				dma->ref = 1;
   676				alloc_frag->offset = sizeof(*dma);
   677	
   678				rq->last_dma = dma;
   679			}
   680	
   681			++dma->ref;
 > 682			*sg_addr = (void *)(dma->addr + alloc_frag->offset - sizeof(*dma));
   683		} else {
   684			*sg_addr = head + alloc_frag->offset;
   685		}
   686	
   687		buf = head + alloc_frag->offset;
   688	
   689		get_page(alloc_frag->page);
   690		alloc_frag->offset += size;
   691	
   692		return buf;
   693	}
   694	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki