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Message-ID: <20230719070450-mutt-send-email-mst@kernel.org>
Date: Wed, 19 Jul 2023 07:05:50 -0400
From: "Michael S. Tsirkin" <mst@...hat.com>
To: kernel test robot <lkp@...el.com>
Cc: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
virtualization@...ts.linux-foundation.org,
oe-kbuild-all@...ts.linux.dev, Jason Wang <jasowang@...hat.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
On Wed, Jul 19, 2023 at 06:33:05PM +0800, kernel test robot wrote:
> 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));
> | ^
yea these casts are pretty creepy. I think it's possible dma_addr_t won't fit in a pointer
or a pointer won't fit in dma_addr_t.
>
> 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
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