CVS commit: src/sys/arch/xen/xen

["Taylor R Campbell" <riastradh%netbsd.org@localhost>]

Module Name:    src
Committed By:   riastradh
Date:           Sat Feb 25 00:34:13 UTC 2023

Modified Files:
        src/sys/arch/xen/xen: xennetback_xenbus.c

Log Message:
xennetback(4): Fix xennetback_evthandler loop.

- After observing the other side has produced pending tx requests by
  reading sring->req_prod, must issue xen_rmb before touching them.

  Despite all the effort to use the heavy-weight
  RING_FINAL_CHECK_FOR_REQUESTS on each request in the loop, this
  barrier was missing.

- No need to update req_cons at each iteration in the loop.  It's
  private.  Just update it once at the end.

- After consuming requests, must issue xen_wmb before releasing the
  slots with RING_FINAL_CHECK_FOR_REQUEST for the other side to
  reuse.

XXX pullup-8 (requires patch; at least add xen_rmb between
    RING_FINAL_CHECK_FOR_REQUESTS and RING_COPY_REQUEST)
XXX pullup-9 (requires patch; at least add xen_rmb between
    RING_FINAL_CHECK_FOR_REQUESTS and RING_COPY_REQUEST)
XXX pullup-10


To generate a diff of this commit:
cvs rdiff -u -r1.108 -r1.109 src/sys/arch/xen/xen/xennetback_xenbus.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.