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/20240327155750-mutt-send-email-...@kernel.org/ PATCH[1] 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[2] drops the local variable @last_avail_idx since it's equivalent to vq->last_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 (3): vhost: Drop variable last_avail_idx in vhost_get_vq_desc() vhost: Improve vhost_get_avail_head() vhost: Reformat vhost_{get, put}_user() Michael S. Tsirkin (1): vhost: Improve vhost_get_avail_idx() with smp_rmb() drivers/vhost/vhost.c | 215 +++++++++++++++++++----------------------- 1 file changed, 97 insertions(+), 118 deletions(-) Changelog ========= v2: * Improve vhost_get_avail_idx() as Michael suggested in [1] as above (Michael) * Correct @head's type from 'unsigned int' to 'int' (l...@intel.com) -- 2.44.0
