Re: [PATCH V2 19/19] virtio_ring: add in order support

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

Hi Jason,

kernel test robot noticed the following build warnings:

[auto build test WARNING on mst-vhost/linux-next]
[also build test WARNING on linus/master v6.15 next-20250528]
[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/Jason-Wang/virtio_ring-rename-virtqueue_reinit_xxx-to-virtqueue_reset_xxx/20250528-144806
base:   https://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git linux-next
patch link:    https://lore.kernel.org/r/20250528064234.12228-20-jasowang%40redhat.com
patch subject: [PATCH V2 19/19] virtio_ring: add in order support
config: arm-randconfig-002-20250528 (https://download.01.org/0day-ci/archive/20250528/202505282256.MVII3mpu-lkp@intel.com/config)
compiler: clang version 17.0.6 (https://github.com/llvm/llvm-project 6009708b4367171ccdbf4b5905cb6a803753fe18)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250528/202505282256.MVII3mpu-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@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202505282256.MVII3mpu-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/virtio/virtio_ring.c:2109:40: warning: variable 'id' is uninitialized when used here [-Wuninitialized]
    2109 |                 BAD_RING(vq, "id %u out of range\n", id);
         |                                                      ^~
   drivers/virtio/virtio_ring.c:60:32: note: expanded from macro 'BAD_RING'
      60 |                         "%s:"fmt, (_vq)->vq.name, ##args);      \
         |                                                     ^~~~
   include/linux/dev_printk.h:154:65: note: expanded from macro 'dev_err'
     154 |         dev_printk_index_wrap(_dev_err, KERN_ERR, dev, dev_fmt(fmt), ##__VA_ARGS__)
         |                                                                        ^~~~~~~~~~~
   include/linux/dev_printk.h:110:23: note: expanded from macro 'dev_printk_index_wrap'
     110 |                 _p_func(dev, fmt, ##__VA_ARGS__);                       \
         |                                     ^~~~~~~~~~~
   drivers/virtio/virtio_ring.c:2075:19: note: initialize the variable 'id' to silence this warning
    2075 |         u16 last_used, id, last_used_idx;
         |                          ^
         |                           = 0
   1 warning generated.


vim +/id +2109 drivers/virtio/virtio_ring.c

  2069	
  2070	static void *virtqueue_get_buf_ctx_packed_in_order(struct vring_virtqueue *vq,
  2071							   unsigned int *len,
  2072							   void **ctx)
  2073	{
  2074		unsigned int num = vq->packed.vring.num;
  2075		u16 last_used, id, last_used_idx;
  2076		bool used_wrap_counter;
  2077		void *ret;
  2078	
  2079		START_USE(vq);
  2080	
  2081		if (unlikely(vq->broken)) {
  2082			END_USE(vq);
  2083			return NULL;
  2084		}
  2085	
  2086		last_used_idx = vq->last_used_idx;
  2087		used_wrap_counter = packed_used_wrap_counter(last_used_idx);
  2088		last_used = packed_last_used(last_used_idx);
  2089	
  2090		if (vq->batch_head == num) {
  2091			if (!__more_used_packed(vq)) {
  2092				pr_debug("No more buffers in queue\n");
  2093				END_USE(vq);
  2094				return NULL;
  2095			}
  2096			/* Only get used elements after they have been exposed by host. */
  2097			virtio_rmb(vq->weak_barriers);
  2098			vq->batch_head = le16_to_cpu(vq->packed.vring.desc[last_used].id);
  2099			vq->batch_len = le32_to_cpu(vq->packed.vring.desc[last_used].len);
  2100		}
  2101	
  2102		if (vq->batch_head == last_used) {
  2103			vq->batch_head = num;
  2104			*len = vq->batch_len;
  2105		} else
  2106			*len = vq->packed.desc_state[last_used].total_len;
  2107	
  2108		if (unlikely(last_used >= num)) {
> 2109			BAD_RING(vq, "id %u out of range\n", id);
  2110			return NULL;
  2111		}
  2112		if (unlikely(!vq->packed.desc_state[last_used].data)) {
  2113			BAD_RING(vq, "id %u is not a head!\n", id);
  2114			return NULL;
  2115		}
  2116	
  2117		/* detach_buf_packed clears data, so grab it now. */
  2118		ret = vq->packed.desc_state[last_used].data;
  2119		detach_buf_packed_in_order(vq, last_used, ctx);
  2120	
  2121		update_last_used_idx_packed(vq, last_used, last_used,
  2122					    used_wrap_counter);
  2123	
  2124		LAST_ADD_TIME_INVALID(vq);
  2125	
  2126		END_USE(vq);
  2127		return ret;
  2128	}
  2129	

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