vhost: move smp_rmb() into vhost_get_avail_idx()

All callers of vhost_get_avail_idx() use smp_rmb() to
order the available ring entry read and avail_idx read.

Make vhost_get_avail_idx() call smp_rmb() itself whenever the avail_idx
is accessed. This way, the callers don't need to worry about the memory
barrier. As a side benefit, we also validate the index on all paths now,
which will hopefully help prevent/catch earlier future bugs.

Note that current code is inconsistent in how the errors are handled.
They are treated as an empty ring in some places, but as non-empty
ring in other places. This patch doesn't attempt to change the existing
behaviour.

No functional change intended.

Signed-off-by: Michael S. Tsirkin <[email protected]>
Reviewed-by: Gavin Shan <[email protected]>
Acked-by: Will Deacon <[email protected]>
Message-Id: <[email protected]>

0 files changed, 0 insertions, 0 deletions