This is suggested by Michael S. Tsirkin according to [1] and the goal is to apply smp_rmb() inside vhost_get_avail_idx() if needed. With it, the caller of the function needn't to worry about memory barriers. Since we're here, other cleanups are also applied.
[1] https://lore.kernel.org/virtualization/20240327075940-mutt-send-email-...@kernel.org/ PATCH[1] drops the local variable @last_avail_idx since it's equivalent to vq->last_avail_idx PATCH[2] improves vhost_get_avail_idx() so that smp_rmb() is applied if needed. Besides, the sanity checks on the retrieved available queue index are also squeezed to vhost_get_avail_idx() PATCH[3] improves vhost_get_avail_head(), similar to what we're doing for vhost_get_avail_idx(), so that the relevant sanity checks on the head are squeezed to vhost_get_avail_head() PATCH[4] Reformat vhost_{get, put}_user() by using tab instead of space as the terminator for each line Gavin Shan (4): vhost: Drop variable last_avail_idx in vhost_get_vq_desc() vhost: Improve vhost_get_avail_idx() with smp_rmb() vhost: Improve vhost_get_avail_head() vhost: Reformat vhost_{get, put}_user() drivers/vhost/vhost.c | 199 +++++++++++++++++++----------------------- 1 file changed, 88 insertions(+), 111 deletions(-) -- 2.44.0
