Re: [PATCH v2 2/2] virtio: silence KCSAN warning in virtqueue_kick_prepare

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

Hi Johannes,

kernel test robot noticed the following build errors:

[auto build test ERROR on linus/master]
[also build test ERROR on v6.19-rc7]
[cannot apply to mst-vhost/linux-next next-20260127]
[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/Johannes-Thumshirn/virtio-silence-KCSAN-warning-in-virtqueue_get_buf_ctx_split/20260127-235023
base:   linus/master
patch link:    https://lore.kernel.org/r/20260127152524.200465-3-johannes.thumshirn%40wdc.com
patch subject: [PATCH v2 2/2] virtio: silence KCSAN warning in virtqueue_kick_prepare
config: sh-allmodconfig (https://download.01.org/0day-ci/archive/20260128/202601282030.CWdibo9B-lkp@intel.com/config)
compiler: sh4-linux-gcc (GCC) 15.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260128/202601282030.CWdibo9B-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/202601282030.CWdibo9B-lkp@intel.com/

All errors (new ones prefixed by >>):

   drivers/vhost/vringh.c: In function '__vringh_notify_enable':
>> drivers/vhost/vringh.c:559:33: error: lvalue required as unary '&' operand
     559 |                 if (putu16(vrh, &vring_avail_event(&vrh->vring),
         |                                 ^
   drivers/vhost/vringh.c:562:36: error: lvalue required as unary '&' operand
     562 |                                    &vring_avail_event(&vrh->vring));
         |                                    ^


vim +559 drivers/vhost/vringh.c

f87d0fbb579818f Rusty Russell      2013-03-20  542  
f87d0fbb579818f Rusty Russell      2013-03-20  543  static inline bool __vringh_notify_enable(struct vringh *vrh,
b9f7ac8c72894c1 Michael S. Tsirkin 2014-12-12  544  					  int (*getu16)(const struct vringh *vrh,
b9f7ac8c72894c1 Michael S. Tsirkin 2014-12-12  545  							u16 *val, const __virtio16 *p),
b9f7ac8c72894c1 Michael S. Tsirkin 2014-12-12  546  					  int (*putu16)(const struct vringh *vrh,
b9f7ac8c72894c1 Michael S. Tsirkin 2014-12-12  547  							__virtio16 *p, u16 val))
f87d0fbb579818f Rusty Russell      2013-03-20  548  {
f87d0fbb579818f Rusty Russell      2013-03-20  549  	u16 avail;
f87d0fbb579818f Rusty Russell      2013-03-20  550  
f87d0fbb579818f Rusty Russell      2013-03-20  551  	if (!vrh->event_indices) {
f87d0fbb579818f Rusty Russell      2013-03-20  552  		/* Old-school; update flags. */
b9f7ac8c72894c1 Michael S. Tsirkin 2014-12-12  553  		if (putu16(vrh, &vrh->vring.used->flags, 0) != 0) {
f87d0fbb579818f Rusty Russell      2013-03-20  554  			vringh_bad("Clearing used flags %p",
f87d0fbb579818f Rusty Russell      2013-03-20  555  				   &vrh->vring.used->flags);
f87d0fbb579818f Rusty Russell      2013-03-20  556  			return true;
f87d0fbb579818f Rusty Russell      2013-03-20  557  		}
f87d0fbb579818f Rusty Russell      2013-03-20  558  	} else {
b9f7ac8c72894c1 Michael S. Tsirkin 2014-12-12 @559  		if (putu16(vrh, &vring_avail_event(&vrh->vring),
f87d0fbb579818f Rusty Russell      2013-03-20  560  			   vrh->last_avail_idx) != 0) {
f87d0fbb579818f Rusty Russell      2013-03-20  561  			vringh_bad("Updating avail event index %p",
f87d0fbb579818f Rusty Russell      2013-03-20  562  				   &vring_avail_event(&vrh->vring));
f87d0fbb579818f Rusty Russell      2013-03-20  563  			return true;
f87d0fbb579818f Rusty Russell      2013-03-20  564  		}
f87d0fbb579818f Rusty Russell      2013-03-20  565  	}
f87d0fbb579818f Rusty Russell      2013-03-20  566  
f87d0fbb579818f Rusty Russell      2013-03-20  567  	/* They could have slipped one in as we were doing that: make
f87d0fbb579818f Rusty Russell      2013-03-20  568  	 * sure it's written, then check again. */
f87d0fbb579818f Rusty Russell      2013-03-20  569  	virtio_mb(vrh->weak_barriers);
f87d0fbb579818f Rusty Russell      2013-03-20  570  
b9f7ac8c72894c1 Michael S. Tsirkin 2014-12-12  571  	if (getu16(vrh, &avail, &vrh->vring.avail->idx) != 0) {
f87d0fbb579818f Rusty Russell      2013-03-20  572  		vringh_bad("Failed to check avail idx at %p",
f87d0fbb579818f Rusty Russell      2013-03-20  573  			   &vrh->vring.avail->idx);
f87d0fbb579818f Rusty Russell      2013-03-20  574  		return true;
f87d0fbb579818f Rusty Russell      2013-03-20  575  	}
f87d0fbb579818f Rusty Russell      2013-03-20  576  
f87d0fbb579818f Rusty Russell      2013-03-20  577  	/* This is unlikely, so we just leave notifications enabled
f87d0fbb579818f Rusty Russell      2013-03-20  578  	 * (if we're using event_indices, we'll only get one
f87d0fbb579818f Rusty Russell      2013-03-20  579  	 * notification anyway). */
f87d0fbb579818f Rusty Russell      2013-03-20  580  	return avail == vrh->last_avail_idx;
f87d0fbb579818f Rusty Russell      2013-03-20  581  }
f87d0fbb579818f Rusty Russell      2013-03-20  582  

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